Status of Research in Cleft Lip and Palate: Anatomy and Physiology," Part 2

NOTE: PART 1 OF THIS REPORT WAS PUBLISHED IN VOLUME II, OC- TOBER, 1974 ISSUE OF THE CLEFT PALATE JOURNAL. ~

DAVID R. DICKSON, Ph.D. J. C. B. GRANT, M.C., M.B., Ch.B., FR.C.S. HARRY SICHER, M.D., D.Sc. E. LLOYD DUBRUL, D.D.S., Ph.D. JOSE PALTAN, M.D. Pitisburgh, Pennsylvania

IV. THE TONGUE

Normal In general, little research on the anatomy and physiology of the human tongue has been found. Therefore, development of the tongue as well as its anatomy and physiology will be covered to give as clear a picture as possible of the paucity of research in this important area. While some foreign language research has not yet been translated for the purpose of this review, no studies of human tongue embryology have been found. Many research reports on tongue structure and function have been published. However, few of these concern the basic anatomy of the human tongue and only the genioglossus muscle has been studied electromyo- graphically. A good deal of research has demonstrated major differences in muscular, vascular, and neural structure of the tongue among sub-human animals and between subhuman animals and man. For example, muscle spindles have been found in the human but not in the cat tongue. Many animals, excepting man, have a posterior branch from the hypoglossal nerve to the tongue. Yet the literature is replete with studies of cats, dogs, etc., which tend to generalize to human. For these reasons only human studies will be reviewed except for embryogenesis where no human studies have been found. Emsrvyorogy. The embryological derivation of the tongue can be considered in terms of 1) surface epithelium, and 2) underlying viscera, primarily musculature. No experimental embryological studies have been found on the tongue epithelium. Five studies involving lingual muscular development, four on the chick, and one on the cat, have been found and will be reviewed. Hunter (34) traced the myotome components of the occipital somites along their migration path in the chick embryo and described their contribution to the hypoglossal musculature. Although no mention is made concerning methodology, it is obvious from the accompanying illustrations that the authors performed a histologic study. The authors state that the hypoglossal musculature in the chick is derived * The subcommittee presenting this report (see Part 1, Volume 11 of the Cleft Pal- ate Journal, October, 1974) was part of a larger group, the Committee on Clinical Re- search in Cleft Lip and Cleft Palate, the work of which was supported by contract NIH- 71-643 awarded by NIDR to the American Speech and Hearing Association. The Com- mintsae findings were summarized in Volume 10 of The Cleft Palate Journal (April, 19783). 131 132 Dickson and others from downgrowth of the 'first seven myotomes, with myotomes three, four, and five as major contributors and myotomes one, two, six, and seven as minor contributors. Bates (3) provides an excellent historical review of the controversy surrounding the origin of the hypoglossal musculature of mammals. He states that "there is general agreement that the hypoglossal musculature of all vertebrates below mammals is derived from the somites of the embryo" but that the origin of this musculature in mammals has been a subject of controversy with two major groups of opposing opinions: the first, that the hypoglossal musculature of mammals is also derived from the somites as first proposed by Froriep in 1885; the second, that the tongue musculature simply differentiates out of local mesenchyme as proposed by Lewis in 1910 and by Pons-Tortella in 19836. Bates studied the early hypoglossal musculature of 35 cat embryos (11 somite stage to the 9 millimeter stage) which were fixed, stained, and serially sectioned. He traced the developing hypoglossal mesenchyme condensations from the ventro- lateral edges of the involved somites to their eventual destination in the pharyngeal floor. He stated the first six somites, four occipital and the first two cervical, give rise to the hypoglossal muscles in the cat, with the first occipital somite being rudimentary. Deuchar (20) performed an experiment which he states eliminated a problem found in the studies of Bates (3) and Hunter (84): the difficulty of differentiating the hypoglossal rudiments from the surrounding tissue. Deuchar operated on 10-12 mm chick embryos and inserted carbon particles into one of the first three posterior otic somites with a needle. He then reinoculated the embryos three to four days; those embryos surviving the procedure for three to four days (25 percent) were fixed, embedded, sectioned, stained, and observed. In 21 out of the 25 processed embryos, carbon had reached the tongue region and was specifically localized here with hardly any occurring in other parts of the pharynx. Deuchar draws the conclusion from these studies that the occipital somites do indeed participate in the formation of the tongue musculature. In both Bates and Hunter, the authors observed what they took to be migration of somitic mesenchyme from the occipital somite region into the region of the embryonic tongue. The hypoglossal mesenchyme appeared slightly darker than the surrounding tissue, thus making differentiation possible. The same type of phenomena (apparent migration) could have been observed if the mesenchyme differ- entiated and proliferated along a linear path from occipital to lingual region, with no actual migration involved. For this reason the study of Deuchar is especially valuable in proving migration of the precursor somites or myotomes. Hammond (28) tried to ascertain the role of the occipital somites in the formation of the hypoglossal musculature by surgically removing the somites unilaterally in chick embryos and observing resultant deficiencies in the tongue musculature of the same side. He unilaterally extirpated the dorsal and medial portions (the dermamyotome) of the anterior six or seven somites in 85 chick embryos of eight to twenty-five somites. The embryos were sacrificed six to nine days later and fixed, embedded, sectioned and stained. Only 29 of the embryos showed any degree of hypoglossal muscle deficiency. Of the five glossal muscles in the chick which the author lists, only one, the copuloentoglossal, was absent (in one-third of the embryos) and only two others, the styloentoglossal and thyroentoglossal muscles, were reduced (in almost all of the 29 embryos). The author stated that the failure to show more extensive reductions may have been due to the difficulty in realizing a complete and clean extirpation of the somites involved. This absence of complete removal was shown in a related study in eight embryos whose somites were surgically removed; later (two to 48 hours) when the embryos were examined, small portions of the myotomes were observed still present. From his experimental data, Hammond concluded that extirpation of somites two through six (or their myo- STATUS OF RESEARCH 133 tomes) is followed by absence or reduction of hypoglossal musculature in the chick and that these studies provided proof that the hypoglossal musculature in the chick takes origin from myotomes of somites two through six. Hammond's study has if anything created more doubt about the somitic origin of the hypoglossal musculature than before. In only 29 of 85 embryos was the hypoglossal musculature affected at all, and only in nine embryos was any muscle totally absent. It is possible that simply the trauma involved could have inhibited the tongue muscle formation to the degree observed. A simple control test could have been performed to determine this. From the data presented in this experiment one could just as easily have concluded that since in the majority (56 out of 89) of embryos no loss of hypoglossal musculature was seen after extirpation of somites two through six, the occipital somites play no role in the formation of the tongue muscles. Hazelton (29) described the migration pattern and fate of cells of the occipital somites and their overlying ectoderm in the chick embryos which had been marked with tritium labeled thymidine. The somites were transferred from labeled donor embryos to host embryos, which were incubated, sacrificed, and the migration pattern of the labeled cells determined radioautographically. The labeling operation was performed at the six to eight somite stage. The transfer operation was performed three to four hours later. The second to fourth or fifth occipital somites plus overlying ectoderm was removed as a single entity from the unlabeled host and replaced with comparable segments from the labeled donor embryos. Incuba- tion periods after transplantation ranged from 15 minutes to five days. Of two hundred experiments carried out, 30 were successful (the embryos survived until sacrificed). The embryos were sacrificed, fixed, sectioned and analyzed. The authors found active proliferation and migration of the labeled cells of the myotomic portion of the somites from their preliminary site in the occipital region to the floor of the mouth, where they united with their fellow of the opposite side. Hazelton carried out a further experiment, transplanting only the labeled overlying ectoderm, to determine its contribution to the observed migration phenomenon; the labeled ectoderm did not participate in the hypoglossal migration. PaTrerns or MovemENnt. Many studies beginning in the early 1800's have been designed to investigate movement patterns of the human tongue in speech and in swallowing. Some of them, most notably MacNeilage and Shales (88), have ascribed various movement to specific tongue muscles. However, little anatomical work has been completed on the human tongue. In addition, research which has been reported on tongue anatomy stresses its extreme complexity with interweaving of muscles in the body of the tongue. For these reasons, the validity of assigning specific tongue movement patterns to specific muscles is highly questionable. Analysis of movement patterns of the tongue is also difficult. Kent and Moll (86) have made significant progress in developing methodology for meaningful study in this area. As important as this type of information is to an understanding of speech and swallowing behavior, the status of basic anatomic and physiologic information regarding the tongue does not permit more than speculation regarding the muscular bases for these movement patterns. Pruystiorogy. While a few surface electromyographic studies of the tongue have been reported, only four studies have been found in which the authors attempted to isolate the activity of specific muscles. Three of these studies (8, 18, 48) found genioglossus to be active during inhalation. Through the use of surface electrodes, MacNeilage and Shales speculated on the roles of each of the tongue muscles during vowel production. Their anatomical descriptions, and therefore the validity of their speculations, were based on the research of Abd-El-Malek (1). However, Abd-El-Malek does not present the source of his data, that is, whether based on one tongue or many, nor does he give any information on anatomic variability. Also, since MacNeilage and Shales placed 134 Dickson and others electrodes in a single parasagittal plane on the dorsum of the tongue, it is difficult to conceive how they could have isolated the several intrinsic muscles or could have derived any data relative to extrinsic muscles.

ANATOMY Dimensions: Four studies have been found concerning tongue dimension. Hopkin (83) measured 32 neonatal tongues (16 male, 16 female; age range from birth to 15 days) and 30 adult tongues (14 male, 16 female; age range 29-85 years) post- mortem. Hopkin found that the mean dimensions of the adult tongue were double those of the neonate. Kunimoto (87) derived slightly smaller measures among Japanese adults than did Hopkin among his North American adults. In a third study, Hopf and Edzard (32) measured six Negro and one Japanese specimen. However, the measurement points were not defined. Bell (4) histologically studied the muscle patterns and fiber diameters of seven neonatal and six adult tongue tips, all formalin fixed. He found that the average fiber diameter almost doubled (25 microns to 47 microns) from newborn to adult, and that histological patterns of newborn and adult tongue tips displayed a definite similarity. The observation error in measured fiber diameters was five microns. Although simplistic in nature, the relationship between the doubling of fiber diameter (4) and the doubling of the tongue in all dimensions (Hopkin 33) between neonate and adult appears interesting. Connective tissue skeleton: The connective tissue skeleton of the tongue is important in understanding glossal musculature because it not only surrounds and separates various muscles, but also serves as a site of attachment in certain in- stances. Three experimental studies found to date mention specific parts of the connective tissue skeleton of the tongue. Dontenwill (21) examined the histological and functional structure of the lingual fascia as well as their relations to the lingual muscles. Dontenwill states that the membranous layer of the lingual fascia is thickest in the area of the V-shaped sulcus terminalis and it becomes thinner toward the tip and sides of the tongue, fading away at the margins. He also states that this layer consists of a network of bundles of collagen fibers through which the muscular fibers of their tendons pass. Abd-El-Malek (1) studied the human tongue by gross microscopic dissections and histological methods. He describes the tongue musculature and its relations to the lamina propria in detail, but gives no indication of the number of tongues observed or variability encountered. He states that the lamina propria becomes gradually thicker and stronger on the dorsum of the tongue as it extends from its root to its tip (opposite the findings of Dontenwill) where it forms a cap-like thickening which is more extensive ventrally than dorsally. To this so- called "anterior arch", he says, are attached the anterior aspects of the longitudinal muscle fibers. His lamina propria is seen on the ventral tongue back to the lingual frenum. Abd-El-Malek also lists the median, paramedian, hypoglossal, and lateral septa of the tongue. His midline medial septum, strongest in its middle portion, is clearly seen in the anterior two-thirds of the tongue. It gives attachment to the medial part of the transverse lingual muscle, and ventrally it intervenes between and is coterminous with the two genioglossus muscles. Posteriorly it consists of a very loose areolar tissue. Dorsally it is practically absent. Abd-El-Malek does not give specific superior, inferior, and posterior limits, but his illustrations indicate that the median septum is attached anteriorly to the anterior arch. He found the paramedian septum to be the strongest septum of the tongue, especially at its posterior part, where it is called the hypoglossal membrane. It molds itself on the lateral surface of the genioglossus muscle, with its narrow apex reaching as far forward as, and corresponding in extent with, this muscle. Posteriorly, it broadens in a horizontal direction and is attached to the hyoid bone, this part being called the hypoglossal membrane; laterally it reaches the submucous layer and intermuscular septa of the muscles of the floor of the mouth. The lateral septa, triangular in shape STATUS OF RESEARCH 135 with its apex directed anteriorly is attached to the paramedian septum medially. Its lateral border is divided into lateral and medial lamellae, and posteriorly it is continuous with the posterior part of the paramedial septum. Salter (47), in a gross and histological study of the human tongue meluded a description of its connective tissue aspects. He gives no information about numbers of specimens or about variational anatomy. Salter lists the connective tissue components as the median fibrous septum, hypoglossal membrane, and submucous areolar tissue. The median fibrous septum is described as springing from the anterior surface of the hypoglossal membrane, and passing forward between the two genioglossus muscles as far as their genial origin, upwards to the dorsum as far forward as its center, and then to the anterior free border of the genioglossi. He found it thick and dense behind and below, gradually becoming thinned out as it spread upwards and forwards; as it got thinner it became cribriform to allow passage of the transverse muscle fibers of the tongue. He states that, without exception, the median septum does not give attachment to any transverse fibers, they all pass through without any break in their medial plane. Salter lists the hypoglossal membrane as a vertical transverse lamina of very dense areolar tissue passing upwards from the upper border of the body of the hyoid bone into the tongue sometimes as far as an inch. Posteriorly it is in relation with the upper part of the epiglottis; it immediately underlies the glossoepiglottic folds. This author also describes the condensed submucous areolar tissue of the tongue as being thickest on the upper surface, especially toward the middle. Musculature: Four studies from the eighteen-hundreds were found which describe specific tongue musculature. Sommering (61) concluded from studies of fresh human tongues that vertical muscle fibers did not exist. However, Cruveilheir (17) and Hesse (80) both show histologic sections which they felt demonstrated a vertical muscle. The work of Salter (47) is presented in the Todd Cyclopedia of Anatomy and Physiology. While no research design is presented, it is apparent that Salter's descriptions are based on gross and histologic dissections of human material. He describes the superior longitudinal muscle as thin posteriorly, becoming thicker toward the tongue tip. He states that it arises from the hyoglossal membrane and tunica propria. Salter describes the inferior longitudinal as extending from tongue base between genioglossus and hyoglossus to the inferior surface of the tongue tip with intermediate attachments to the cutis of the tongue. The transverse muscle of the tongue is described by Salter as passing from the submucous fibrous tissue of one side of the tongue through the fenestrated median septum to the opposite side. He goes on to describe in detail the relationships of the vertical, transverse, and longitudinal intrinsic fibers at different points in transversely sectioned human tongues. Just anterior to the free margin of the genioglossus, his tongue in cross section consists of a muscular cortex and medulla (which he calls the lingual nucleus of Bauer). The medulla consists of tightly interwoven vertical and transverse fibers at right angles, with no longitudinal fibers intervening. The superior and inferior cortices consist of longitudinal fibers regularly interrupted by vertical fibers. The lateral cortices consist of longitudinal fibers regularly interrupted by transverse fibers. The superolateral and inferolateral cortices consist of longitudinal fibers interrupted by interwoven vertical and transverse fibers. Just behind the anterior free margin of the genioglossus the appearance is similar to that above except the bilateral genioglossus muscle passes vertically upwards to insert into and contribute to the vertical fibers of the inferior border. A section made near the base of the tongue shows the cortical portion nearly lost superiorly but greatly accumulated laterally with obliquely vertical fibers abundant and transverse fibers nearly lost. With regard to the extrinsic muscles, Salter describes the anterior genioglossus as passing upward and forward to the dorsum of the tongue, contrary to Cruveil- heir's (17) opinion (as stated in Salter) that it travels on the ventral surface to the tip of the tongue. Salter states that the two genioglossus muscles may be separated 136 Dickson and others up to the point of their insertion into the tongue; beyond that line their separation is no longer possible. For having entered the tongue they come into relation with the transverse intrinsic fibers, with which they interlace at right angles forming part of the vertical muscle. Salter finds no disposition to lateral divergence in any part of the genioglossus; on the contrary, its direction is rather upwards and inwards throughout. Salter states that the most inferior fibers of genioglossus insert into the hyoglossal membrane with some fibers immediately above passing backward and to the sides of the pharynx where, uniting with the middle constrictor, they form the geniopharyngeus of Winslow. Salter describes hyoglossus as arising from the lateral part of the body sand greater cornu of the hyoid, and passing upward to enter the tongue between inferior longitudinal and styloglossus. He states that Albinus has described and named the hyoglossus as three distinct muscles: one, the ceratoglossus, arising from the greater cornu; another, the basioglossus, from the body; and a third, intermediate, the chondroglossus, taking its origin from the lesser cornu. The portions from the body and greater cornu Salter describes as being separated below by a cellular interval and above by a few fibers of the styloglossus which pass inbetween. He states that after the styloglossus reaches the base of the tongue, a few of its fibers bend inwards, the majority being continued longitudinally along the side of the tongue, mingling with fibers of the hyoglossus and inferior longitudinal having a similar direction. Historically, the next article which was found, that of Abd-El-Malek in 1939, (1) is perhaps the most frequently referred to by modern authors. Abd-El-Malek studied the human tongue musculature by gross microscopic directions and by histologic methods. He describes the tongue musculature and its relations to the lamina propria and septa in detail. Unfortunately, like Salter, Abd-El-Malek gives no indication of the number of tongues examined nor does he deal with anatomic variability. With regard to the superior longitudinal, he states that its fibers, in the same location, are divided by interruption of the genioglossus. He describes the muscle as thin only in its periferal parts, but in the middle two-fourths as a bulky mass triangular in cross section with its apex ventral. He states that its posterior attachment is the lamina propria of the posterior third of the tongue back to the lower part of the epiglottis and hyoepiglottic ligament, and partly to the hyoglossal membrane with its anterior fibers attached to the dorsal lamina propria and to the anterior arch. Abd-El-Malek describes the inferior longitudinal as a narrow muscle, oval in cross section, extending between the paramedian septum and the medial lamella of the lateral septum. He states that posteriorly it generally possesses two attachments, medial and lateral. The medial part arises in conjunction with the most lateral and ventral fibers of the genioglossus, with whose fibers it decussates, from the anterior surface of the hyoid bone. Its lateral attachment is from the root of its great cornu, together with the most medial of the decussating fibers of the hyoglossal muscle. As it proceeds forward, the inferior longitudinal partially rotates inferomedially and about its middle it blends with the anterior fibers of genioglossus, hyoglossus, and styloglossus with which it forms the ventral part of the tongue tip. Contrary to the report of Salter, Abd-El-Malek describes the transverse muscle as extending from the median septum laterally, with some fibers ending on neighbor- ing muscles and their septa, others extending to the lamina propria of the side of the tongue. Abd-El-Malek lists two sets of vertical muscle fibers, both of which, he says, decussate intimately with the transverse fibers. His "long" set reaches the lamina propria dorsally and the submucous layer ventrally. The rest fall short between the paramedian septum and adjacent muscle septa. Genioglossus is described by Abd-El-Malek as constituting the main bulk of the tongue posteriorly, being present in all transverse and horizontal sections and all parasagittal sections except the most lateral. In the main he agrees with Salter's STATUS OF RESEARCH 137 description except for his finding that genioglossus radiates mediolaterally, especially in the intermediate and posterior parts of the tongue. In describing hyoglossus, Abd-El-Malek states that the anterior portion interdigitates at its origin with the geniohyoid, and that the posterior part interdigitates with the inferior longitudinal muscle. He describes the anterior fibers running nearly longitudinally toward the tip of the tongue with styloglossus and inferior longitudinal to the anterior arch to which they are attached. Its posterior fibers, which lie under the cover of styloglossus with which they decussate, radiated nearly transversely and posteriorly toward the root of the tongue, decussating again with the lateral part of the inferior longitudinal muscles medially. Both middle and posterior fibers are partly attached to the paramedian septum and partly after decussation join the fibers of the superior longitudinal dorsally and the transverse and genioglossus ventrally. Finally, Abd-El-Malek (1) describes the styloglossus after reaching the tongue as dividing into two parts, "upper" and "lower"; the "lower is smaller and decussates superficially with the lateral surface of the hyoglossus, the "upper" proceeds toward the tip where its deep fibers interdigitate with the same muscle. At the anterior border of the hyoglossus the styloglossus is enlarged to a ventral direction and winds around the lateral and ventral parts of the tongue until it gains its inferior surface. It then insinuates itself among the anterior fibers of the genioglossus, hyoglossus, and inferior longitudinal muscles, joining together to be attached to the anterior arch. The following year Keaster (86) reported her study of the intrinsic muscles of the tongue. Unfortunately she did not present any of her own findings. Neither did she document any of her long treatise on phylogenetic development of the tongue. - In 1951, Dabelow (19) presented a study of the interconnections of the lingual muscles and their relationships with the lingual septa based on histologic sections of fetuses and newborn infants. While a complete translation of his work was not available for the purpose of this report, his work is detailed and well documented. Among other findings, he agreed with Salter that the median septum "is no fibrous dividing wall but a complicated linkage of the transverse muscles." He also reported that the deep fibers of superior longitudinal are continuous with fibers of styloglossus. De Paula Assis (1954), based on a study of sixty human specimens, described the normal anatomy of the palatoglossus. He found its fibers to mix with those of styloglossus upon entering the lateral margin of the tongue. No substantial differences were found based on race, sex, or age. Another often quoted study, that of Strong (62), was published in 1956. He dissected 0.5 cm. sections of four and one-half month human fetal tongues with attention only to the vectors of the intrinsic muscles. He does not indicate the number of specimens dissected, nor does he deal with variability. He mentions "sub-aponeurotic short imbricated bows" of superior longitudinal. He illustrates the transverse muscle as extending from the median septum to the lateral lamina propria. In the tip of the tongue, in front of the termination of the median septum, he describes and illustrates a unique arrangement of muscle fibers which he places with the transverse system. Such fibers, he states, are attached to the aponeurosis near the juncture of the lateral and middle dorsal thirds of the tongue half, pass through the mid-region of the tongue, and attach to the opposite lateral inferior surface near the juncture of its middle and lateral thirds. Bell (4) in a histologic study of seven neonatal and six adult human tongue tips found that while muscles could, in his opinion, be identified, individual intrinsic groups would not be traced due to complicated interlacing of fibers. He reported clear evidence of vertical muscle fibers, and direct insertion of muscle fibers into the reticular lamina propria on the dorsal but not the ventral surface. Doran and Baggett (22) described the genioglossus in several animals, including 138 Dickson and others man, and found its fibers to stop short of the tongue tip. They also described three distinct sites of mandibular attachment. Unfortunately they do not give any information on subjects or variability. A few other old studies have been located but are, at this time, untranslated. However, the above review does seem an accurate representation of the status of information. Nerve and Blood Supply: There was not time, for this review, to thoroughly search the older foreign literature on tongue innervation and blood supply. Thus far, detailed anatomical studies of the distribution of lingual nerves and blood vessels have not been found. Weddell et al., (66) do report on a nerve study based on anesthetization and conclude that the lingual and inferior alveolar nerves do not cross midline in the anterior two-thirds of the tongue. A number of investigators have looked for muscle spindles in the tongue. While some authors (see review by Weddell, et al., (66) have not found spindles in human tongues, others (14, 16, 24, 25, 55) have found them. Cooper found spindles in a number of muscles in the tongue but reported that there are few spindles in the anterior third of the tongue. She also reported finding ganglia on the lingual nerve in the base of the tongue and on the glossopharyngeal nerve in the tongue. Bielik (6) reported on 25 human dissections, but confined his observations of anastomoses between the mylohyoid and lingual nerve which he found to occur in 16% of his dissections. Sussman, Hanson, and MacNeilage (65) reported on an investigation of single motion units in tongue, and Sussman (638) provides an excellent and integrative review of research pertaining to neuromuscular control of tongue activity. Rakhawy (45) reported on a study of phosphotases in nerve tissue of the human tongue and stated that his evidence suggests that the lingual ganglia studied were parasympathetic rather than sensory. In the literature reviewed to date, only Abd-El-Malek (7) gives any description of blood vessel dissection. , Oturr Puyvsionrocicam StupIEs. While studies of tongue and lip pressure and force, and studies of intra-oral perception are beyond the seope of this review, two excellent sources are available for information in these areas. Richard L. Chris- tiansen (15) has written an excellent review of pressure and force studies. The two volumes on oral stereognosis edited by Bosma (9, 10) present much of the collected work in that area. A few studies have been published in these areas since the reviews cited: (2, 26, 27, 48, 44, 46, 49, 50).

Cleft While a number of investigators (6, 11, 12, 138, 283, 81, 89, 40, 42) have investigated tongue position in the speech of cleft palate persons, there is still a lack of detailed specific information on what characterizes lingual patterning in cleft palate, even though there is evidence that it may differ from normal. The experimental methods of Kent (86) on tongue movement of normals will hopefully be applied to the cleft palate population. Experimental studies of the anatomy and physiology of the tongue in cases of cleft palate have not been found. However, preliminary investigations by one of the reviewers (Dickson) suggest that anatomical differences may occur in the tongues of cleft palate persons.

Discussion The paucity of basic normative information on human tongue anatomy and physiology is obvious. In spite of the work of Salter and Abd-El-Malek, we still do not have a clear picture of even the basic structure of the tongue. Further, there is good evidence (7) that subhuman animal studies will not suffice. Until reliable normative data is established, studies of abnormality can not be intelligently planned. STATUS OF RESEARCH 139

References . ABD-E1-MAarEx, S. Observations on the morphology of the human tongue. J. Anat., 73, 201-210, 1989. . AnprEws, J. R., Oral form discrimination in individuals with normal and cleft palates. Cleft Palate J ., 10, 92-98, 1973. . BaTEs, N. B., The early development of the hypoglossal musculature in the cat. Amer. J. Anat., 83, 329- 345, 1948. . BELL, W. A., Muscle patterns of the late fetal tongue tip. Angle Orthod., 40, 262-265, 1970. i= . BErrv, M. F., Lingual anomalies associated with palatal clefts. J. Speech Dis., 14, 359-362, 1949. Ou . P., Observacédes sobre a anastomose entre o n. mylohyoideus e o n. lingualis em negros et mulatos O Brasileiros. Ann. Paculd. Med. Univ. Sao Palo, 14, 85-111, 1989. . Brom, S., anp S. Sxocuun, Some observations on the control of the tongue muscles. Experientia (Basal), 15, 12-13, 1959. . Bors, C. T., anp M. A. Electromyography of the genioglossus muscles in man. J. Applied Physiol., 21, 1695-1698, 1966. . Bosma, J. F. (Ed.), Symposium on Oral Sensation and Perception, Charles C. Thomas, Springfield, IIl. 1967. . BosmaA, J. F. (Ed.), Second Symposium on Oral Sensation and Perception, Charles C. Thomas, Springfield, Ill., 1970. . Brooks, A. R., R. L. Surmron, K. A. Youncstrom. Compensatory tongue-palate-posterior pharyngeal wall relationships in cleft palate. J. Speech Hear. Dis., 30, 166-173, 1965. . Buck, M., Facial skeletal measurements and tongue carriage in subjects with repaired cleft palate. J. peech Hear. Res., 18, 121-132, 19583. 183. Buck, M., Velopharyngeal movements and tongue carriage during speech in adults with unrepaired in- complete cleft palates. Cleft Palate Bull., 10, 8-10, 1960. 14. CECCHKERELLT, G., Contributo alla conoscenza delle expansioni nerrose di senso nella mucosa del cavo orale e della lingua dell'luomo. Int. Mschr. Anat. Physiol., 265, 2738-350, 1908. 15. CuristiansEn, R. L., Some biologic considerations in orthodontic research. Amer. J. Orthod., 60, 329-343, 1971. 16. CoorE®Rr, S., Muscle spindles in the intrinsic muscles of the human tongue. J. PAysiol., 122, 198-202, 1953. 17. CrUvEILHEIR, J. Anatomy of the Human Body, Trans. by G. 8. Pattison, Harper and Bros., New York, 1844. 18. Cunrninenxam, D. P., aAnp J. V. BasmaJI&AN, Electromyography of genioglossus and geniohyoid muscles during deglutition. Anat. Rec., 165, 401-409, 1969. 19. Darrow, R., Vorstudien zu einter betrachtung der zunge als funktionelles system. J. Morphol. Micro- scap. Anat., 91, 3-76, 1951. 20. DEtcHAR, E. M., Experimental demonstration of tongue muscle origin in chick embryos. J. Embryol. Exp. Morphol., 6, 527-529, 1958. I 21. DonNTENWILL, W., Die funktionelle morphologie der tunica propria linguae beim menschen, Acta Anat., 8, 156-167, 1949. 22. Doran, G. A., anp H. Baga®tr, The genioglossus muscle: A reassessment of its anatomy in some mammals, including man. Acta Anat., 83, 403-410, 1972. 28. FALK, M. L., anp G. A. Kopp, Tongue position and hypernasality in cleft palate speech. Cleft Palate J ., 5, 228-287, 1968. 24. ForstER, Zur Kenntnis der muskelspindln, Virckow's Arch., 187, 121-154, 1894. 25. FraAnNqu®r, O. Von, Beitrage zur kenntnis der muskelknospen. A muscle spindle in human tongue. Phys. Med. Gesch. Wurzburg, 24, 19-48, 1891. 26. Fuccr, D., Oral vibrotactile sensation: An evaluation of normal and defective speakers. J. Speech Hear. Res., 16, 179-184, 1972. Fucer, D. J., D. E. HALL, AND F. F. WEmmER, Normative study of oral and non-oral structures using vibro-

27. I tractile stimuli. Percep. Motor Skills, 33, 1099-1105, 1971. 28. Hammonp, W. S., Origin of hypoglossal musculature in chick embryos. Anat. Rec., 161, 547-557, 1965. 29. HazEuron, R. D., A radioautographic analysis of the migration and fate of cells derived from the occipital somites in the chick embryo with special reference to the development of the hypoglossal musculature. J. Embryol. Morphol., 24, 455-466, 1970. 30. HEssE, Fr., Uber die muskeln der menschlichen zunge. Z. Anat. Eniw., 1, 80-160, 1875. 31. Hixon, E., An X-ray study comparing oral and pharyngeal structures of individuals with nasal voices and individuals with superior vorces. Unpubl. M.S. Thesis, State Univ., Iowa, 1949. 32. Hopr, K., D. Enzarv, Beobacht ungen fiber die verteilung der zungenpapillen bei verscheidenen men- schenrassen. Z. Morphol. Antropol., 12, 545-557, 1910. 38. Hopkin, G. B., Neonatal and adult tongue dimensions. Angle Orthod., 87, 132-183, 1967. 34. HunTEr, R. P., The early development of the hypoglossal musculature in the chick. J. Morphol., 57, 472-491, 1985. 35. KrErastERr, J., Studies on the anatomy and physiology of the tongue. Laryngoscope, 50, 222-257, 1940. 36. Kent, R. D., Ano K. L. Morr, Cineflucrographic analyses of selected lingual consonants. J. Speech Hear. Res., 15, 453-473, 1972. 37. Kuntromo, K., Uber die zungen papillen und die zungengrosse der Japaner. Z. Morphol. Anthrop., 14, 3839-366, 1912. 140 Dickson and others

38. MacNzrItAcE®, P. F., ano G. N. Sanes, An electromyographic study of the tongue during vowel production. J. Speech Hear. Res., 7, 200-232, 1964. 39. Marrarws, J., ano M. C. Byrn®, An experimental study of tongue flexibility in children with cleft palates. J. Speech Hear. Dis., 18, 43-47, 19583. 40. McKEE, T. L., A cephalometric radiographic study of tongue position in individuals with cleft palate deformity. Angle Orthod., 26, 99-109, 1956. 4 pa . Mirn®, I. M., anv J. F. Curaruu, Cinefluorographic study of functional adaptation of the oropharyngeal structures. Angle Orthod., 4, 267-283, 1970. 42. Nomurstronm, P. H., anv B. D. AnpErson, A functional cephalometric radiographic investigation of the nasal and oral pharyngeal structures during deglutition in operated cleft palate and non-cleft palate persons. Oral Surg. Oral Med. Oral Path., 12, 142-155, 1959. 43. PRoOFFIT, W. R., Lingual pressure patterns in the transition from tongue thrust to adult swallowing. Arch. Oral Biol., 17, 555-563, 1972.

44. H Putnam, A. H. B., anp R. L. Rinaru, Some observations of articulation during labial sensory depriva- tion. J. Speech Hear. Res., 15, 520-542, 1972. 45, Rarmnawy, M. T., Phosphotases in the nervous tissue. Acta Anat., 83, 356-366, 1972.

46. C> Rinaru, R. L., et al., Some relations between orosensory discrimination and articulatory aspects of speech production. J. Speech Hear. Dis., 35, 3-11, 1970. 47. Sauter, H. H. Tonauv®. Todd Cyclopedia of Anatomy and Physiology, Longman, Brown, Green, and Long- mans, London, 4, 1120-1163, 1852. 48. SAUERLAND, E. K., anp 8. P. MitcuEruLt, Electromyographic activity of the human genioglossus muscle in response to respiration and to positional changes of the head. Bull. Los Angeles Neurological Soc., 85, 69-73, 1970. 49. Scott, C. M., ano R. L. Rinaeru, Articulation without oral sensory control. J. Speech Hear. Res., 14, 804- 818, 1971 a 50. Scort, C. M., anp R. L. Rinarut, The effects of motor and sensory description on speech. A description of articulation. J. Speech Hear. Res., 14, 819-828, 1971 b. 51. SommEring, S. T., Vom ban des menschlichen korpers. Muskellehre, 3, 1-392, 1841. 52. Strona, L. H., Muscle fibers of the tongue functional in constant production. Anat. Rec., 126, 61-79, 1956. 53. Sussman, H. M., What the tongue tells the brain. Psychol. Bull., 77, 262-272, 1972. 54. Sussman, H. M., R. J. Haxnsoxr, anp P. F. MacNEmacE®, Studies of single motor units in the speech musculature: Methodology and preliminary findings. J. Acoust. Soc. Amer., 51, 1872-1374, 1972. 55. WarkEr, L. B., ano M. D. Rasacorar, Neuromuscular spindles in the human tongue. Anat. Rec., 133, 438, 1959. 56. WreppErLt, G., et al., The innervation of the musculature of the tongue. J. Anat., 74, 255-267, 1940.

V. THE LARYNX Up to the present time the reviewers and their associates have found and reviewed over 200 references on the innervation of the larynx and over 300 references in the English language alone on the non-neurological anatomy of the larynx. Approximately one-third of the latter represents experimental studies. The re- mainder are case studies or surgical reports. While some of the foreign literature on the non-neurological anatomy of the larynx has been reviewed, this review is not complete. However, recent research on the anatomy of the muscles, ligaments, and joints of the human larynx has clarified the current status of information in this area. Further, electromyographic studies of the laryngeal musculature have only been undertaken in the past thirty years. These studies have all been reviewed. Thus, while the present review does not represent all of the literature which has ever been written on laryngeal anatomy and physiology, it is quite likely that it does represent our current status of information. Only experimental articles of particular relevance or significance to this paper will be specifically referred to here.

Normal EnmmBrvorogy. In 1972, over sixty years after the classical work of Frazer (41) in the development of the human larynx, Hast (61) stated that "in the study of the developmental anatomy of the human, one of the most neglected organs has been, and still is, the larynx . . . where study of the earlier [embryologic] stages was made by the 'classical' investigators, conclusions can be tenuous since findings were derived from an examination of only 5 to 10 representative specimens covering STATUS OF RESEARCH 141 all stages of development." Also, in 1972, Tucker and O'Rahilly (185) stated that "although the larynx was the first portion of the respiratory tree to be studied developmentally in the human, it has not previously been described in a clearly graded series of specifically staged human embryos." These two studies by Hast (61) and Tucker and O'Rahilly (1385) are an encouraging thrust into this complex area. The information they contain is far from complete, but these studies and others will hopefully continue. Soustin (126) in his study of Laryngeal epithelium also adds important developmental information. In 1970, J. Wind (145) published his monumental treatise "On the Phylogeny and the Ontogony of the Human Larynx" in which he reviews over 600 references on this subject and presents his own data from reconstruction of human larynges in the embryonic period. Much of the very old work on the larynx not included in this review is synthesized in Wind's work. Parrerns or MovEmENt. Various methods have been employed for the study of the living human larynx. Foremost among these have been laryngeal photography (30, 87, 52, 87, 100, 101, 107) and various X-ray techniques (1, 2, 8, 69, 60, 62, 71, 95, 99, 110, 112, 123, 140). Some of these studies have involved simultaneous evaluation of acoustical, electrical, and air-flow data. They have provided ample evidence for the validity of the myoelastic-aerodynamic theory of voice production and have provided indisputable evidence against the neurochronaxic theory of voice production. (Husson, 1951). Based on this literature there is evidence to support the following contentions regarding normal laryngeal function. First, there is a basic difference in the laryngeal mechanisms for biologic closure (e.g., respiration, gag, cough, swallow, and the Valsalva maneuver) and for phonation. The former movements are far more gross in nature. Their total purpose is to accomplish complete and sustained closure of the glottis as in the case of building up intrathoracic and intra-abdominal pressure, to maintain adequate opening of the glottis as during respiration, or to close the larynx in swallowing. The descriptions of Ardran and Kemp (2, 3, 4), Shelton, Bosma, and Sheets (1960), and Steward (129) are illustrative of this mechanism. In contrast, phonatory movements of the larynx seem to involve more highly discreet cooperative functions of the laryngeal muscles for the control of pitch and intensity. These movements were first described by Hodgkinson (1895) who utilized laryngoscopy to observe movements of indigo powdered particles on the surface of the vocal folds during phonation. While the mechanism for pitch and intensity adjustment are not completely understood, the movement patterns associated with these changes seem to be fairly well defined. It is accepted that the vocal folds adduct at the initiation of phonation (37), that sufficient impedance is established at the vocal folds so that as air pressure builds up beneath them with expiratory effort they are blown apart (1386, 138) and that their return to closure is a function of the original adductory force and the Bernoulli effect. Hollien, (69) found that the vocal folds are shorter during phonation than in any condition of abduction, that pitch rise is accompanied by vocal fold lengthening in the normal pitch register, that the length of the vocal folds increases systematically with increases in pitch, but that no single pattern of elongation or shortening is consistent in the falsetto register. He also found that the magnitude of the lengthening is no greater in one portion of the pitch range than in any other and suggested that increases in vocal pitch are accompanied by increase in vocal fold elasticity with simultaneous decrease in vocal fold mass. It is also evident from the studies cited above that motion at the cricothyroid joint has a direct effect on vocal fold length. There is, however, some dispute among investigators as to whether cricoarytenoid joint movement is associated with vocal fold length change while the folds are in the adducted position. Also, from the X-ray and photographic data, there is dispute about the nature of the motion at both of 142 Dickson and others these joints. Motion at the cricothyroid joint has been described as both rotary and sliding. Motion at the cricoarytenoid joint has been described as rocking of the arytenoid cartilage over the rim of the cricoid, sliding of the arytenoid along the facet of the cricoid articulation, and rotation of the arytenoid about a vertical axis. The reason for this dispute is related to difficulty in obtaining good visualization of the laryngeal cartilages in X-ray and difficulty in discerning the exact nature of cartilage movement by direct observation of the larynx from above. More information about the nature of movement at these joints has been gained from anatomical studies which will be reviewed later in this paper.

ANATOMY Cartilages, Ligaments, and Joints: Anatomical studies of the cartilages, joints, and ligaments of the human larynx have been reported (11, 12, 40, 44, 78, 79, 80, 128, 139). With regard to the cricothyroid joint, it has been demonstrated (78, 79) that the structure of the joint and the placement of its ligaments would greatly inhibit sliding motion but do allow free rotation. They also demonstrated that in {fresh human larynges taken at autopsy rotation of the joint produced up to 25% length change in the vocal folds. This degree of change is consistent with that observed in the living larynx. Motion at the cricoarytenoid joint is described traditionally as rotatory about a vertical axis through the joint (24, 180), or as a combination of rotation and sliding along the long axis of the cricoid facet (101), or as sliding only (88). The experimental work of Snell, (121); von Leden and Moore, (189); Sonesson, (124); Maue, (78); and Maue and Dickson, (79), has demonstrated that the primary motion at this joint is posterolateral to anteromedial rocking of the arytenoid cartilage over the cricoid facet. The work of the latter authors has indicated that this type of motion is quite free in the fresh autopsy larynx but sliding of the arytenoid along the axis of the cricoid is minimal and that rotation of the arytenoid about a vertical axis does not seem to be possible. This type of rocking motion was first suggested in 1879 by Illingworth. Thus, there is ample anatomical evidence that cricothyroid joint movement can create changes in vocal fold length and that cricoarytenoid motion can produce abduction and adduction of the vocal folds but probably cannot account for changes in vocal fold length in the adducted position. Musculature: While standard texts of anatomy describe a number of muscles intrinsic to the vocal folds and the lateral walls of the larynx, Leidy in 1846 (738) pointed out that some of these divisions of laryngeal musculature are not found in anatomical dissection. For example, he found no anatomical basis for differentiating thyroarytenoid and vocalis. He further considered thyroepiglottic and aryepiglottic as extensions of the thyroarytenoid muscle. Maue and Dickson (79) have gone a step further in suggesting that dissections of human and subhuman larynges suggest that the lateral cricoarytenoid, thyroarytenoid, thyroepiglottic and aryepiglottic muscles may be viewed as a single muscle complex. Sonesson (125) and Rossi, Giovanni, and Cortesina (105) have studied the relationship of the vocalis muscle to the vocal ligament and present excellent reviews of the literature on this topic. There seems to be ample evidence that vocalis does not attach to the vocal ligament but that some of its fibers do attach to the conus elasticus. A comprehensive review of the literature on the anatomy of the aryepiglottic fold is provided by Cleary (22), and a review of the literature on the extrinsic laryngeal muscles, their attachments and their function is given by Sokolowsky (122). Minnigerode (88) recently studied the structure of the cricopharyngeus muscle. From a mechanical standpoint the work of Maue and Dickson (79) suggests that the combination of the thyroarytenoid muscle mass and the interarytenoid muscle mass can provide an adductory STATUS OF RESEARCH 143 foree on the arytenoid cartilages in direct opposition to the abductory force provided by the posterior cricoarytenoid. Innervation: As pointed out by Lam and Ogura (72), the diverse functions served by the human larynx (i.e. cough, reflex closure of the glottis, the Valsalva maneuver, maintenance of vocal fold tonus, phonation, and the automatic functions of neuromuscular, neurovascular, and neuro-secretory reflex activities) presuppose a complex system of neuronal connections and pathways. Investigation of these parameters of laryngeal innervation has been extremely limited to man, and, as indicated earlier in this report, since there is no proof of equivalence between man and experimental animals, much of the information which has been gained from animal studies in this area must be viewed with extreme caution in a description of human laryngeal neurology. Delevan (26), Bertrand (16), Lam and Ogura (72), and Furstenberg and Magiel- ski (42) have attempted to define the central pathways involved in laryngeal innervation. There is general agreement that the movements of the intrinsic laryngeal muscles are under fine pyramidal tract control and that the specific neural pathway involved is the common pyramidal tract, which ultimately ends in the upper portion of the medulla oblongata in the region of the nucleus ambiguus. This nucleus is the origin of the lower motor neurons which enter the glossopharyngeal, vagus, and accessory nerves and which ultimately furnish the motor and sensory innervation to the larynx. The peripheral innervation of the human larynx is far more accessible for research and has received substantially greater attention than the central innervation (15, 74, 75, 76, T?, 90, 92, 108, 109, 141, 148). It has also been investigated by White (142), Donaldson (27, 28), Simanowski (120), Rustad and Morrison (108), Tomasch and Britton (184), Faaborg-Andersen and Buchthal (83), Bowden and Scheuer (18), Konig and von Leden (67, 68), Rossi and Cortesina (105), and Wyke (146). The peripheral innervation of the human larynx may be summarized grossly by tracing the course and termini of the laryngeal nerves from their origin in the nucleus ambiguus as fibers of cranial nerve XI. Fibers destined for the larynx leave the nucleus ambiguus as part of cranial nerve XI. These fibers then leave cranial nerve XI and join the fibers of cranial nerve X at the nodose ganglion. This ganglion gives rise to the superior laryngeal nerve, the recurrent laryngeal nerve, and the pharyngeal nerve. The superior laryngeal nerve divides into the internal and external laryngeal nerves. The internal branch is generally considered to supply the mucosa of the epiglottis and the larynx superior to the glottis. The external branch supplies the cricothyroid muscles and some fibers of the inferior constrictor. The internal branch usually enters the larynx by way of the thyroid membrane and then splits into three branches: the rami anterior, media, and posterior. Ramus anterior is thought to supply the epiglottis; ramus media the aryepiglottic fold, and the laryngeal vestibule; and ramus posterior the arytenoid region, some of its twigs piercing the arytenoid muscle and supplying the inner surface of the arytenoid cartilage and some of the other twigs anastomosing with branches of the inferior laryngeal nerve in the arytenoid muscles (Galen's anastomosis). The external branch of the superior laryngeal nerve enters and supplies the cricothyroid muscle and is a motor division whereas all of the branches of the internal branch of the superior laryngeal nerve are sensory in function. The recurrent laryngeal nerve terminates in the laryngeal mucosa inferior to the glottis and in the various intrinsic laryngeal muscles with the exception of the cricothyroid. The recurrent laryngeal nerve typically divides into two branches before entering the larynx; its anterior ramus supplies the homolateral posterior cricoarytenoid, arytenoid, lateral cricoarytenoid, and the thyroarytenoid muscles; its posterior ramus forms Galen's anastomosis with a branch of the superior laryngeal nerve. There is 144 Dickson and others still a substantial degree of disagreement about this "typical" picture of human laryngeal innervation, however. While this is the "typical"" presentation of human laryngeal innervation usually described, it is far from being a documented consensus. The course of the innervation from the medulla to the larynx has been fairly well documented with the exception of its course through the pharyngeal plexus and the pattern of the sympathetic innervation to the larynx, but there are still numerous questions about the specific termini of laryngeal nerves within the larynx, about specific nerve functions, and about specific nerve distribution within the larynx. For example, the possibility of double motor innervation of the interarytenord muscles is a recurring issue in the literature. Some researchers state that the interarytenoids are supplied bilaterally by both the left and right recurrent laryngeal nerves. Others state that the interarytenoid muscles are innervated unilaterally by each recurrent laryngeal nerve. Still others contend that the interarytenoid muscle receives motor fibers from the internal branch of the superior laryngeal nerve. Vogel (137) and Clerf (238) state that they have demonstrated motor endplates within the interarytenoid muscle of man, proof of double innervation of the muscle by recurrent and superior laryngeal nerves, while other researchers including Lemere (74, 75, 76), Meurman (85), and Williams (1438) have been unable to demonstrate any contractions of the interarytenoid muscle by direct stimulation of the superior laryngeal nerve, and thus contend that this muscle does not receive motor innervation from the superior laryngeal nerve. As pointed out by Pressman and Keleman (102), even if stimulation of the superior laryngeal nerve does produce contraction of the interarytenoid muscle, it is not proof that motor fibers pass into it from this nerve because the stimulation could produce afferent sensory stimulation of the recurrent laryngeal nerve and thus result in reflexive contraction of the interarytenoid muscle. It is apparent in the literature on laryngeal innervation that there is still no consensus about either sensory-motor subdivisions of the laryngeal nerves or about the innervation supplying specific structures within the larynx (106). For example, innervation of the laryngeal mucosa has been attributed to (a) a combination of the external laryngeal (ie., external branch of the superior laryngeal nerve), the internal laryngeal (ie., the internal branch of the superior laryngeal nerve), and the recurrent laryngeal nerve (ie., Gegenbaur, (94); (b) a combination of the external and internal laryngeal nerves only (ie., Testus, from Onodi1, (94); (c) the internal laryngeal nerve only (ie., St. Clair Thomson, and Negus, (128); and (d) the internal laryngeal and recurrent nerves only (i.e., Arnold, (6). The latter concept has received the greatest support recently. The specific motor-sensory divisions of the laryngeal nerves have likewise been disputed. The internal laryngeal nerve is thought by some researchers to be sensory only (13). By other researchers the internal laryngeal nerve is thought to be a mixed nerve (94). The former view has received the most support recently. The external laryngeal nerve has likewise been the object of dispute. It is said to be a mixed nerve by some authors (128). By other researchers it is considered to be motor to the cricothyroid muscle only (138). The recurrent laryngeal nerve is said by some researchers to be mixed (18). Others consider it to be exclusively motor (128). The strongest research support would indicate that the recurrent laryngeal nerve is a mixed nerve which supplies motor innervation to all of the intrinsic laryngeal muscles except the cricothyroid, which is supplied by the external laryngeal nerve, and that it supplies sensation to the larynx from the level of the glottis downward. Sensation from the glottis upward is supplied by the internal laryngeal nerve. Equally divergent opinions are expressed on the final termin of the various branches of these nerves within the intrinsic laryngeal muscles. It has been stated that the anterior branch of the internal laryngeal nerve supplies the epiglottis and STATUS OF RESEARCH 145

aryepiglottic fold, that the medial branch supplies the mucosa of the posterior cricoid area and sensation down to the level of the vocal folds, and that the posterior branch unites with the posterior branch of the recurrent nerve to form Galen's anastomosis. Other references indicate that the aryepiglottic fold is supplied by the medial branch of the internal laryngeal nerve, and that the posterior branch assists in supplying the posterior cricoid area and sensation down to the level of the vocal folds. There is little dispute, however, over the destination of the external laryngeal nerve; it supplies the motor innervation to the cricothyroid muscle and to part of the inferior constrictor. Interestingly, while there is general agreement in the literature that the posterior (medial) branch of the recurrent laryngeal nerve supplies the motor innervation to the interarytenoid and posterior cricoarytenoid muscles and that the anterior (lateral) branch supplies the lateral cricothyroid and thyroarytenoid muscles, innervation of thyroepiglottic and aryepiglottic muscles is not described, nor is the innervation of the ventricular folds. The lack of information on the thyroepiglottic and aryepiglottic musculature may well reflect the amount of experimentation on innervation in experimental animals, which do not possess these two muscles. Pressman and Keleman (102) stated that movements of the ventricular folds still occur when the recurrent laryngeal nerve is paralyzed, and concludes that the superior laryngeal nerve must be at least partially involved in motor innervation of the ventricular fold. Galen's anastomosis, mentioned previously, is another area of laryngeal neurology which has been the subject of extensive discussion in the literature. It forms the most consistent connection between the internal laryngeal nerve and the recurrent and is usually stated to contain descending sensory fibers from the internal laryngeal nerve (1.e., New, 1923). Langer (94) believed, however, that it also contained motor fibers, since he considered the internal laryngeal nerve to be a mixed nerve. Babes (from Onodi, (94), Onodi (94), and Lemere (74, 75)) considered the anastomosis to be mainly composed of descending and ascending sensory fibers and possibly also a few autonomic fibers. In man Galen's anastomosis is considered to be rudimentary (74, 75), supplying only the mucosa of the posterior cricoid area and of the cervical esophagus. The contribution of the sympathetic nervous system to the control of the larynx has been alluded to in the preceding discussion. This has been described in detail by Mitchell (1954) and Johnson (64). It appears to be a consensus in the literature that filaments from the superior cervical ganglion join either the superior laryngeal nerve or its external branch directly, or pass through the pharyngeal plexus and thus reach the larynx indirectly. Frequently some of the sympathetic fibers run for a short distance with the superior cervical sympathetic ganglion before branching off to join the superior laryngeal nerve. Other branches derived from the parent external carotid cardiovascular and subclavian plexus travel with the superior thyroid arteries, receiving fibers from the middle cervical sympathetic ganglion en route to the larynx. The sympathetic system is responsible for secretomotor functions of the larynx, as described by Johnson (64). While there does not seem to be any focused disputes in the literature over the course and basic functions of the sympathetic system supplying the larynx, it is also obvious that the variability in its specific pattern of branching has not been well defined, nor has its course through, and contributions from, the various plexes been well defined. The nerve muscle fiber ratio is presumed to be lower in man than in any of the experimental animals used for studies of innervation (cat, dog, monkey, goat, sheen, pig), and to be highest within the thyroarytenoid muscle in man. It has been estimated to average 1:20. Another question which has not been settled is the division pattern of the laryngeal nerve as it enters the larynx. According to some authors, it divides into abductor and adductor branches; according to Williams (144) it divides into motor and sensory branches. The latter view has received the greatest support. 146 Dickson and others

Finally, there has been a great deal of dispute over whether or not there are muscle spindles in the intrinsic laryngeal muscles. The consensus would seem to be that there definitely are spindles in all of the intrinsic laryngeal muscles. While three investigators (14, 46, 47), found no spindles in the larynx, spindles have been found in the intrinsic muscles examined by Goerttler (45), Paulsen (96), Bowden, ef al. (19), Keene (66), Konig and von Leden (67, 68), Rossi and Cortesina (105), Grim (48), Baken and Noback (10), and Baken (9). In view of this, it is very surprising that there is practically no mention in the literature reviewed of the possibility of a gamma efferent system of innervation to the intrinsic laryngeal muscles. This would seem to be inevitable, since neural control of the larynx is extraordinarily complex and would appear to involve both kinestheses (conscious, cortical responses) and proprioception (subconscious responses cerebellar and medullary control) as well as spinal level reflexes. Only one author mentions the gamma efferent system in connection with laryngeal innervation, and he states that there is no evidence to suggest that it is present. Sutton, Larson, and Farrel (131) recently studied motor units in the human cricothyroid muscle. Blood Supply: The blood supply of the larynx has received less attention by researchers than any other area of laryngeal anatomy and physiology except perhaps for dimensions and mechanical parameters of the hard tissue components. Only seven studies specific to laryngeal blood supply were found in a search of the literature from 1750 to 1973: Dwight (81); Carco (21); Hansel (60); Terracol and Guerrier (133); Schechter and Ogura (111); Shin, et al. (115); and Speiden, Tucker, and Soulen (127). Terracol and Guerrier (133) refer to descriptions of the blood supply given by Luschka, Broeckaert, and Salmon. They also cite the work of Vulpian (1875), Hedon (1894), Broeckaert and Terracol (1930, 19831, 1932), and Azemar (1937) on vasomotor innervation of the larynx. The general pattern of the vessels supplying the larynx has been fairly well laid out by these authors. The superior thyroid artery, which emanates from the common carotid on the left and from the subclavian on the right, gives rise to the hyoid, sternocleidomastoid, superior laryngeal, cricothyroid, muscular, and glandular arterial branches. The superior laryngeal artery thus supplies the muscles of the hyoid bone and larynx, the laryngeal mucosa, the thyroid gland and the lower part of the pharynx. The hyoid branch anastomoses with its fellow of the opposite side and also with the lingual artery. The cricothyroid artery anastomoses with its fellow of the opposite side and usually also sends small branches into the larynx. There are several variations which have been noted in the literature on the course of the superior laryngeal artery. It may arise directly from the external carotid and it may enter the larynx via the thyroid foramen. The venous supply generally parallels the arterial supply. While there does not appear to be as much dispute in the literature about the blood supply of the larynx as there is about its innervation, there is little information on the variability of the normal vascular pattern, and little on its transmidline distribution. These remain two areas in need of investigation. Muscurar Puystorogy. The following review represents a summary of the highlights of electromyographic findings on the human intrinsic laryngeal muscles with reference to some of the major experimental work in this area. The principal point of agreement in the electromyographic research is that the cricothyroid muscle contracts during phonation and that its degree of activity is directly correlated with vocal frequency (5, 82, 33, 48, 98, 97, 118, 119, 147). Faaborg-Andersen ($2), Shipp (116), Shipp and McGlone (119), and Gay, et al. (43), also found thyroarytenoid muscle contraction to correlate with vocal frequency. Faaborg-Andersen and Buchthal (83), Faaborg-Andersen (82), Hiroto, et al., (56) and Shipp (118) all found that the interarytenoid muscle contracts during phonation. Shipp (118) and Shipp and McGlone (119) found its degree of contraction was not related to vocal frequency while Faaborg-Andersen (32) found some relationship between degree of contraction of interarytenoid and vocal fre- STATUS OF RESEARCH 147

quency but not the same degree as he found for cricothyroid and thyroarytenoid. Posterior cricoarytenoid has been found to be only slightly active or inactive in phonation by Faaborg-Andersen and Buchthal (838), Faaborg-Andersen (82), Hiroto, et al. (66), Shipp (118), and Shipp and McGlone (119). This muscle has been found to be active in inspiration (82, 33, 56). In addition, Shipp (118) and Shipp and McGlone (119) found that the contraction of thyroarytenoid and cricothyroid are correlated with subglottic pressure. They felt that this relationship is responsible for the necessary vocal fold resistance to subglottic pressure required for phonation. Hirose and Gay (65) revealed that "coordinated actions of the abductor and the adductor muscles of the larynx" are related to various type of vocal initiation. Hirose (64) had previously indicated the need for additional study of laryngeal function associated with speech activity. Kotby and Haugen (69, 70) reported on their research beginning with the premise that the posterior cricoarytenoid muscle cannot abduct the vocal folds (though there is a great deal of anatomical and physiological evidence to the contrary). Their results were seemingly so variable and self-contradictory that their conclusions are difficult to evaluate. For example, they report activity from posterior cricoarytenoid during adduction and increasing pitch and cricothyroid activity during anterior separation of the cricoid and thyroid. While Gay, ef al., (438) also reported posterior cricoarytenoid action at high pitch, he found all muscles under study to increase their contraction at highest pitch. This does not necessarily mean that all of these muscles cause pitch increase by their contraction. One study of oxygen consumption and cell biology of laryngeal muscles was found (65) and represents a needed area of further research. One further and very interesting line of research has generated a good deal of interest. That is the effect of aging on voice (29, 365, 36, 61, 81, 82, 88, 86, 91, 103, 118, 182). Unfortunately there has been virtually no study of the anatomy of the developing larynx (7, 113). While not concerned with the intrinsic muscles of the larynx, it should also be noted here that Shipp (116) and Shipp Deutsch, and Robertson (117) have presented electromyographic evidence for the differentiation of function of the inferior constrictor muscle and the cricopharyngeus; Hirano, Loike, and von Leden (538) have studied the sternohyoid muscle during phonation.

Cleft As pointed out by Blumberg, ef al. (17), a total of twelve cases of laryngoesopha- geal cleft, involving cleft of the cricoid lamina along its vertical midline, have been documented in the literature. Richter (104) was the first author to document this defect. It was later described in case studies by Finlay (89), Crooks (25), Pettersson (98), Zachary and Emery (148), and Cameron and Williams (20). Blumberg, et al., (17) has pointed out that only three of these twelve cases occurred in term infants. An additional case report of laryngo-esophageal cleft was documented in 1966 by Shapiro and Falla (114). This is obviously an area in which very little research has been conducted. It would be of interest to know, for example, if there is any correla- tion between laryngeal clefts and clefts of other structures within the oral-facial- pharyngeal-laryngeal complex. No information has been found in the literature relevant to the anatomy and physiology of the larynx in the cleft palate individual. Neither has there been any investigation of the function of the ericopharyngeal muscle in cleft palate. However, laryngeal problems may be associated with cleft palate (84).

Discussion The principal areas of information on the human larynx are such that a great deal of basic anatomical research is still necessary to define laryngeal parameters ickson and others 148 CJ relevant to function. The paucity of developmental information on the larynx is evident. The total lack of research on the larynx of the individual with cleft palate is apparent. However, even with the adult normal larynx, information is necessary to resolve issues of specific muscle morphology and of the distribution of nerves and blood vessels. While electromyographic investigations of the larynx are underway, these analyses of muscle function are far from complete. The information called for is basic to any analysis of the complex interactions of the larynx and the system of which it is a part. Once again the combined efforts of a number of specialties are required in order to advance our knowledge of laryngeal structure and function. The anatomist, the physiologist, the speech pathologist and the surgeon must work together in order to develop and test logical hypotheses relating to normal and pathologic function and methods of surgical and non-surgical management.

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H., Fluoroscopic and spot-film examination of the larynx. Radiology, 79, 969-972, 1962. 118. SEarE, R., Senescence of the vo ce. Eye Har Nose Throat Monthly, 50, 62-68, 1971. 114. SnarIRro, M. J., anD A. Fanta, Congenital posterior cleft larynx. Ann. Otol., 74, 961-967, 1966. 115. Sumn, T., et al., Vasomotor responses to laryngeal nerve stimulation. Arch. Oto-Laryngol., 91, 257-261, 1970. 116. SHmipp, T., EMG of pharyngoesophageal musculature during alaryngeal voice production. J. Speec/. Hear. Res., 13, 184-192, 1970. 117. Smpp, T., W. W. Dratscn, aAnp K. Pharyngoesophageal muscle activity during swallowing in man. Laryngoscope, 80, 1-16, 1970. 118. SHpp, T., anp H. Speech frequency and duration measures as a function of chronological age. J. Acoust. Soc. Amer., 5, 111, 1971. 119. Surp, T., anp R. E. Laryngeal dynamics associated with voice frequency change. J. Speech Hear. Res., 14, 761-768, 1971. 120. SmanowskI, N., Ueber die schwingungen der stimmbaender bei laebumungen verschiedener kehlkopfmuskeln, PfAlueger's Arch. Physiol., 42, 104-119, 1888. . SxErt, C., On the function of the crico-arytenoid joints in the movements of the vocal cords. Proc. Kon. Nederl. Acad. Wet., 50, 1370-1381, 1947. 122. Soxorowsxy, P. R., Effect of extrinsic laryngeal muscles on voice production. Arch. Oto-Laryngol., 38, 355-364, 1943. 1283. SonEsson, B., Die funktionelle anatomie des cricoarytaenoidgelenkes. Z. Anat. Entw., 121, 292-303, 1959. 124. SonrEssorn, B., A method for studying the vibratory movements of the vocal cords; a preliminary report. J. Laryngol., 78, 732-737, 1959. 125. SonrEsson, B., On the anatomy and vibratory pattern of the human vocal folds with special reference to a photo-electrical method for studying the vibratory movements. Acta Otolaryngol., Suppl. 156, 1-80, 1960. 126. SoustIN, V. P., The histochemical characteristics of the epithelium of true vocal cord development of man (Russian). Vestn., 3, 33-36, 1969. 127. SpEipEx, L. M., G. TuckER, Jr., anD R. SouuEn, Angiography of the larynx: An anatomic study in cadaver larynges. Canad. J. Otolaryngol., 1, 219-2283, 1972. 128. Sr. CraIr, T., aAnNDp V. E. NEaus, Diseases of the Nose and Throat. Appleton Century Crofts, Inc., NY, 1949 (p. 535). 129. STUART, A., The mode of closure of the larynx. J. PAystol., 13, 59-60, 1891. 130. SULLIv¥AN, W. W., M. E. Savrer, anp G. Corssen, A study of the rotary component of the motion of the arytenoid cartilages in man. Texas Rep. Biol. Med., 18, 284-287, 1960. 131. Surrox, D., C. R. Larsox, anp D. M. FarrEuLLt, Cricothyroid motor units. Acta Otolaryng., 74, 145-151, 1972. 132. TARLOW, A., A comparative study of the speaking fundamental frequency characteristics of children with cleft palates. Unpubl. M.S. Thesis, Univ. of Wisconsin, 1968. 133. TERrRACOL, J., AND Y. GurrriEr, Vascularization of vocal cords. Ann. Ofolaryngol., 73, 407-4283, 1956. 134. TomascH, J., aND W. A. Brirroxn, A fiber-analysis of the laryngeal nerve supply in man. Acta Anat., 10, 386-398, 1940. 135. TuckER, J. A., anD R. O'Ranxiuuy, Observations on the embryology of the human larynx. Trans. Amer. Laryngol. Assn., 93rd Mtg.: 35-38, 1972. 136. Vax pEn Brra, J. W., J. T. ZantEmMa, anp P. DoornENBAL, On the air resistance and the Bernoulli effect of the human larynx. J. Acoust. Soe. Amer., 29, 626, 1957. 137. VocEt, P. H., The innervation of the larynx of man and the dog. Amer. J. Anat., 90, 427-447, 1952. 138. Von LEpEx, H., The mechanism of phonation. Arch. Otolaryngol., 74, 660-675, 1961. 139. Vox LrEpEx, H., ano P. Moors, The mechanics of the cricoarytenoid joint. Arch. Otolaryngol., 81, 616- 625, 1965. 140. Warp, P. H., et al., Laryngeal and pharyngeal pouches. Surgical approach and the use of cinefluorographic and other radiologic technics as diagnostic aids. Laryngoscope, 73, 564-582, 1963. 141. WeEExs, C., anp J. W. Hmmtonxn, Extralaryngeal division of the recurrent laryngeal nerve. Ann. Surg., 116, 251-258, 1942. 142. WuitE, W. H., Further communication on the function of the recurrent laryngeal nerve with regard to the thyroid body. Brit. Med. J ., 2, 1014, 1885. 152 Dickson and others

143. A. F., The nerve supply of the laryngeal muscles. J. Laryngol. Otol., 65, 3483-348, 1951. 144. Wirr1aMs, A. F., The recurrent laryngeal nerve and the thyroid gland. J. Laryngol. Otol., 68, 719-725, 1954. 145. Winp, J., On the Phylogeny and Ontogeny of the Human Larynz. Wolters-Noordhoff Publ., Groningen, 1970. 146. Wyxx®, B., Recent advances in the neurology of phonation: phonatory reflex mechanisms in the larynx. Brit. J. Dis. Commun., 2, 2-14, 1967. 147. YantiamaRra, N., anp H. von LepEx, The criciothyroid muscle during phonation. Ann. Otolaryngol.. 74, 987-1006, 1968. 148. R. B., anp J. L. EmERy, Failure of separation of larynx and trachea from the esophagus: Persistant esophagotrachea. Surg. 49, 525, 1961.

VI. THE FACE AND MUSCLES OF THE MANDIBLE

Normal Anatomy. In 1931, Ernst Huber (8) published his study of the anatomy and development of the muscles of the face. In that document he not only presents the results of his own extensive work including studies of racial differences, but provides a comprehensive review of literature including phylogenetic considerations and covers over 250 references. Only two studies have been located which antedate his work. In 1962, Martone and Edwards (14) published a description of some of the facial anatomy. However, it was difficult to determine how much of their description was from actual anatomical research. In 1967 Gasser (4) studied the embryologic and fetal development of the facial muscles and provided an excellent review of work done to that time as well as careful descriptions of the 50 specimens which he studied. The only other study of the musculature of the face and mandible which has been found was that of Honee (7). Honee studied the lateral pterygoid muscle bilaterally in five cadavers. He presents detailed descriptions of his findings including estimates of vector and force. Another area of research in which little has been done (22) is the anatomy of the nasal cartilages. It appears that our current concepts in this area derive principally from clinical reports and subhuman research. Even here there is little agreement except on gross form. PHuystorLogy. A number of electromyographic studies have been reported on this musculature. Buccinator has been studied by Lundquist (12) and Sousa and Villi (20). Lundquist found buccinator to be active during sucking, swallowing, and clenching of the teeth. Sousa found that it was active during lateral retraction of the angle of the mouth as well as for lip compression. The masseter muscle has been found to act in occlusion and protraction of the mandible. In occlusion it may be preceded by temporalis and inhibited by tooth contact (5, 6, 18, 15, 17, 19). Tem- poralis has been studied by Moyers, (15); Pruzansky, (19); MacDougall and Andrew, (138); Griffin and Munro, (6); and Perry, (17). It seems evident that the principle role of this muscle is mandibular elevation and retraction. Moyers (15) and Carlsoo (2) studied the action of the pterygoid muscles. Carlsoo found the lateral pterygoid to be active on protrusion and lateralization of the mandible but also found it active "in movements where it has a mechanically antagonistic action." Moyers stated that the external pterygoid contracted prior to the suprahyoids for mandibular depression. It is then followed by the anterior digastric. Elevation of the mandible was found to involve internal pterygoid, but this muscle increased activity when elevation was combined with protrusion. Moyers felt that the pterygoid muscles were principal in mandibular lateralization, aided by temporalis. The two pterygoid muscles were always found to be active for protraction. Carlsoo (1) also found the suprahyoid muscles to be active during mandibular projection and lateral displacement. These descriptions, however, are over-simplified. Moyers (15) and Pruzansky (19) stress the complex interaction of these muscles and the need to view the coordinated working system. STATUS OF RESEARCH 153

Leanderson, Ohman, and Persson (11) in their well-controlled electromyographic study of the lip musculature found that lip closing was related to contraction of depressor anguli oris and mentalis (obicularis oris was not studied) and lip separation to contraction of depressor labii interioris with "probable inhibitions of the depressor anguli oris." They later found lip rounding to be related to contraction of orbicularis oris. Proffit and Norton (18) present an excellent review of the literature pertaining to lingual and labial pressure on the dentition. They conclude that "studies to date have not been designed to test the pertinent variables. Such studies continue to be needed . .."

Cleft Anatomical studies of the face and muscles of the mandible associated with cleft lip and/or cleft palate are few in number and relate almost exclusively to clinical description. Physiologic research in this area, if it exists, has not been found by the reviewers. Fara (3) studied the anatomy and arteriography of the cleft lip in 16 stillborn children with various types of clefts. They report their findings in detail. In general, both the muscle fibers and blood supply followed the cleft margin toward the nasal wing or columella. The muscles on the philtral side of the cleft lip were found to be hypoplastic with poorer arterial supply than on the lateral side in unilateral clefts. In the prolabium of bilateral clefts, the musculature and arterial supply was described as very poor. Perezynska-Partyka and Pruszezsynski (16) reported muscle and "numerous" blood vessels in the bilateral cleft prolabium. In 1949, Huffman and Lierle (9) stated that "in a search of the literature for information concerning the nasal variations that may accompany a unilateral chiloschisis, we were unable to find what we considered a comprehensive and detailed study of the condition."" Unfortunately, the same statement could be made today. From "study of living patients," photographs, masks, and operative experience they described the features of the unilateral cleft lip nose. However, this obviously did not involve controlled dissection and histologic study. Krikun (I0) describes the anatomy of the nose in 64 patients with nasal clefts. It is not clear whether his descriptions are based on speculation from surface anatomy or from actual dissection. Finally, Stark and Kaplan (21) describe the nasal anatomy in two bilateral cleft embryos.

Discussion It is apparent that several major areas of anatomy and physiology relating to face and mandible are in urgent need of research. These include physiological normative studies of all types and basic anatomical, leading to physiological, studies of various types of clefting.

References 1. CarLsoo, S., An electromyographic study of the activity of certain suprahyoid muscles (mainly the anterior belly of digastric muscle) and of the reciprocal innervation of the elevator and depressor musculature of the mandible. Acta Anat., 26, 81-98, 1956 (a). 2. CaARLsOO, S., An electromyographic study of the activity, and the anatomic analysis of the mechanics of the lateral pterygoid muscle. Acta Anat., 26, 339-351, 1956 (b). 3. Fara, M., Anatomy and arteriography of cleft lips in stillborn children. Plast. reconst. Surg., 42, 29-36, 1968. 4. GassEr, R. F., The development of the facial muscles in man. Amer. J. Anat., 120, 357-376, 1967 (b). . Grirrin, C. J., anp R. R. Mauro, Electromyography of the jaw-closing muscles in the open-close-clench Cr cycle in man. Arch. Oral Biol., 14, 141-149, 1969. 6. Hannax, A. G., B. Marturws, axnp R. YEmnm, Changes in the activity of the masseter muscle following tooth contact in man. Arch. Qral Brol., 14, 1401-1406, 1969. 154 Dickson and others

7. Hox®®, G. J. M. L., The anatomy of the lateral pterygoid muscle. Acta Morphol. Neerl.-Scand., 10, 381- 340, 1972. 8. HuBER, E., Evolution of Facial Musculature and Facial Expression. Johns Hopkins Press, Baltimore, 1931. 9. HurrMax, W. C., aAnp D. M. LiEru®, Studies on the pathologic anatomy of the unilateral hare-lip nose. Plast. reconst. Surg., 4, 225-234, 1949. 10. L. A., Clinical features of median cleft of nose. Acta Chir. Plast., 14, 137-148, 1972. 11. LEanpERrsoN, R., anp B. E. F. Muscle activation for labial speech gestures. Acta Otolaryng., 73, 362-373, 1972. 12. Lunpaquist, D. O., An electromyographic analysis of the function of the buceinator muscle as an aid to denture retention and stabilization. J. Prosth. Dent., 9, 44-52, 1959. 13. MacDovaaLL, J. D. B., axnp B. L. AnorEw, An electromyographic study of the temporalis and masseter muscles. J. Anat., 87: 37-45, 19583. 14. MartTon®, A. L., anp L. E. Epwaros, Anatomy of the mouth and related structures. II. Musculature of expression. J. Prosth. Dent., 12, 4-27, 1962. 15. MovyErs, R. E., An electromyographic analysis of certain muscles involved in temporo-mandibular movement. Amer. J. Orthod., 36, 481-515, 1950. 16. PErczynxsra-PartykAa, W., anp M. Pruszczynsk1, Badania mikroskopowe prolabium w obustronnych rozszezepach wargi gornej. Czas. Stomat., 24, 1049-1054, 1971. 17. PErryx, H. T., Muscle contraction patterns in swallowing. Angle Orthod., 42, 66-80, 1972. 18. ProFFIT, W. R., aAnp L. A. Nortoxn, The tongue and oral morphology : Influences of tongue activity during speech and swallowing. ASH A Reports, No. 5, 107-115, 1970. 19. Pruzansxy, S., The application of electromyography to dental research. J. Amer. Dent. Assoc., 44, 49- 68, 1952. 20. Sousa, O. M. pF, anp M. VITTI, Estudo eletromiografico do m. buccinator. O Hospital (Brazil), 68, 105- 117, 1965. 21. Starx, R. B., anv J. M. Kaprax, Development of the cleft lip nose. Plast. reconst. Surg., 61, 413-415, 1973. 22. Straatsma, B. R., anp C. R. Srraatsma, The anatomical relationship of the lateral nasal cartilage to the nasal bone and cartilaginous septum. Plast. reconst. Surg., 8, 443-455, 1951.

VII. GENERAL SUMMARY AND DISCUSSION Today there is a critical need to develop more efficient and effective methods of diagnosis and treatment of persons with cleft palate. It would seem apparent that one of the areas of information necessary to that development is an understanding of how the pre- and post-surgical cleft palate functions in relation to the non-cleft palate and what structural differences occur in the musculature, blood supply, and nerve supply of the cleft palate. However, the palate is only a part of this mechanism. It is imperative to consider not only the palate but all of the oral-facial- pharyngeal-laryngeal system; and, in addition, the respiratory apparatus. The need for further anatomical and physiological research in the areas of normal and cleft palate is apparent. With regard to normal patterns of movement, the specific nature of the lateral pharyngeal wall involvement needs to be further delineated. The site of maximum movement relative to the torus tubarius needs particular attention. Detailed electromyographic investigation of all the muscles of this area is still necessary to resolve the conflicts apparent in the available literature. However, this work must be preceded by or coincident with more detailed anatomical study of the normal mechanism. There is little specific information on the developmental morphology of this musculature. Detailed studies of the palato- pharyngeus, palatoglossus, and uvular muscles are almost non-existent. With regard to nerve supply there is still a need to sort out the pharyngeal plexus and the origins of the vagus nerve. This may be possible through embryologic and fetal studies. Studies of the anatomy and physiology of the palate and pharynx of the person with cleft palate is not nearly as advanced as studies of the normal structure and function. Radiographic and motion picture studies of these movement patterns and their degree of variability needs to be pursued in a manner similar to studies of the normal. The field of electromyography of the cleft palate is practically virgin territory. While some very good information is available on the musculature of the cleft palate, more detailed information is necessary to indicate the degree of varia- STATUS OF RESEARCH 155 bility which should be expected with various types of cleft palate. In addition, no studies of the detailed anatomy of the Eustachian tubes of persons with cleft palate have been found. Nerve supply and blood supply in cleft palate have received very little attention. The need for further research on maxillary growth and development of the maxilla is evident and indicative of similar research which is needed on the whole craniofacial complex, not only to add information where there is none, but to resolve existing conflicts in the literature. With regard to the tongue, the most urgent need in terms of the normal mechanism is for more defined information on the anatomical structure of the human tongue. There is ample evidence of the fact that the structure of the human tongue is unlike that of lower animals in many important ways. Thus animal studies will not suffice. Yet, little human research on tongue anatomy has been reported. Based on this needed research, physiological studies of the normal tongue and anatomical and physiological studies of the tongues on cleft palate persons can be planned. The principle area of information on the human larynx is such that a great deal of basic anatomical research is still necessary to define laryngeal parameters relevant to function. The paucity of developmental information on the larynx is evident. The total lack of research on the larynx of the individual with cleft palate is apparent. However, even with the adult normal larynx, information is necessary to resolve issues of specific muscle morphology, and the distribution of nerves and blood vessels. While electromyographic investigations of the larynx are underway, these analyses of muscle function are far from complete. The information called for is basic to any analysis of the complex interactions of the larynx and the system of which it is a part. In all areas referred to an area of urgent need is developmental morphology. Our interest is directed toward the developing child, yet anatomical research has largely been embryologic or adult. In none of the areas reviewed is there adequate developmental information. While the need for further anatomical and physiological research in the area of face and mandible of both normal and cleft is clear, the most urgent need would seem to be in nasal anatomy where little information, normal or pathological, now exists. In summary, much more attention must be given to the basic structure of this system both in the normal and abnormal. The concentrated effort in this direction seems to these reviewers to necessitate the training of more highly qualified investigators in this area of research. Speech phatologists, dentists, and surgeons who are aware of the clinical problems of management of cleft palate must work together with highly trained anatomical and physiological investigators if problems of clinical significance are to be solved. At the present time few centers in this country are turning out investigators well trained in anatomical and physiological investigations with specific interest and competency in this area. It is suggested then that one of the high priorities should be the training of investigators in anatomy and physiology in an interdisciplinary environment with extensive exposure to speech, dental, and management problems. At the present time these investigations are being carried on by persons from a variety of fields with a variety of back- grounds. Perhaps because of this, these investigators do not commonly communicate with one another. More opportunities for cross fertilization among current investigators should be encouraged. Many programs now train classical anatomists, or classical physiologists, or speech scientists, or medical or speech clinicians. What is lacking is an integrated, multidisciplinary, intensive program of training for the classical anatomist or physiologist, for example, within a clinical setting. There is urgent need for research scientists who can cross the traditional boundaries of 156 Dickson and others the classical biological fields and clinical fields; scientists who can interact with the clinician with knowledge and understanding of management problems faced by the clinician but with thorough, in-depth training in the basic sciences and basic science research. One of the handicapping factors in anatomical research, particularly of cleft palate, is the difficulty in obtaining material for study. Another problem is the expense involved in setting up laboratories for extensive physiological investigation. One way of helping to offset these problems would be to establish a national committee for the registration of material available for study. Such a committee could maintain a record of sources of anatomical material for study and a record of laboratories specifically equipped to do various types of physiological research. Thus, if an experimenter were in need of a specific type of anatomical material or needed processing of data beyond the capacity of his own center, the registry committee could put him in touch with other investigators who could provide material for him or help in the processing of his data. This plan would make two assumptions: First, that current investigators are anxious to work cooperatively, and second, that they would be willing to share materials. In the present reviewers experience both assumptions are true to an extent which would make the formation of such a committee extremely valuable. The suggested committee could serve as a coordinating body to make interdisciplinary contacts among investigators and clinicians much more possible. It should also lead to much more cooperative research. Finally, the need for more basic science oriented interdisciplinary traiming programs has been mentioned. Such training must be interdisciplinary and may most efficiently be interinstitutional. There are a number of examples in this country where a number of training institutions have cooperated in a way which makes it possible for a student to use the facilities of more than one institution depending on his own needs and the strength of the institutions involved. This type of interinstitutional and inter-disciplinary training should be encouraged. The suggested committee could act as an information clear- ing house for the development of these types of programs. Several basic factors seem to emerge from the present review. First, there is still urgent need for further anatomical research in all of the areas covered. Second, normative data must be further developed in order to support study of pathologic conditions. Third, anatomical and physiological research must be coordinated in order to provide meaningful data. Fourth, investigations of muscle function, air flow and pressure, mechanical pressure, acoustics, and movement patterns must be integrated as sufficient basic information is developed to permit such integration. Fifth, basic and clinical scientists must work together to develop and test meaningful hypotheses related to normal and abnormal function, and related to improved methods of diagnosis, prognosis, and treatment of disorders. Sixth, there is an urgent need to train more investigators in depth in the basic sciences, but also in an interdisciplinary environment so that they can serve the needs outlined for interdisciplinary research. Finally, it has been suggested that a national committee could be established to help meet some of the needs reflected in this report.