The Fontanella Metopica and Its Remnants in an Adult Skull

AUTHOR’S ABSTRACT OF THIS PhPER lRSUED BY THE BIBLIOGRAPHIC SERVICE, UECEVBER 15

THE FONTANELLTA METOPICA AND ITS REMNANTS InTAN ADULT SKULL ADOLF H. SCHULTZ Carnegie Institution of Washington

FIVE FIGURES It is not uncommon to find in the skull of a newborn infant a small fontanelle between the two frontalia in their nasal third. This is usually called fontanella metopica (f. medio-frontalis, fonticulus interfrontalis inferior) (fig. 1). A considerable number of skulls, both of childrcn and of adults, showing short, irregular, transverse or V shaped sutures or fissures in the mid- line of the frontal bone abore the level of the superciliary ridges have been described in the literature and interpreted as remilants of thc fontanella metopica. The author has found in the skull of an adult an abnormal suture, which is comparable to those above mentioned, hut which is more extensive than in any of the cams previously described; accordingly its publication appears justifiable. This specimen (fig. 2) belongs to the Anatomical Department of thc Johns Hopkins Medical School and was kindly placed at my disposal by Dr. W. H. Lewis. The skull is that of an American negro, fifty-five years of age. It might be mentioned that the skin over the frontal region was absolutely normal, therefore any external factor, whether acci- dental or surgical (trepanation) can be excludcd as the cause of the anomaly. The greatest length of the skull is 193 mm., the greatest breadth 148 mm., the basion-bregma height 128 mm. and the horizontal circumference 553 mm. The weight of the skull, including the mandible, is 985 grams, a figure, which is close to the upper limit of variation of weight for the human skull. This is an indication of the thickness of the bones of the skull, which is characteristic of the negro. Most of the sutures are 259 260 ADOLF H. SCHULTZ

Fig. 1 Frontal view of the skull of 8 male negro fetus with a fontanella metopica.

Fig. 2 Frontal vicw of the skull of a negro with an abnormal sutme on the frontal bone. FONTANELLA METOPIC-4 IN AN ilDULT SKLTLL 261

obliterated, on the inner surface more than on the outer. This is also true of the internasal suture, although its course can still be recognized (the suture was retouched in fig. 2), and therefore the right nasal bone is found at its upper end to extend far into the left. On each side, at the iiicisura parietalis, there is a Wormian bone. The lambdoid suture is rich in Wormian bones. It is noteworthy that there is present on both sides of the mandible a well pronounced processus anguli mandibulae (apophysis lemurica) , which points downward and outward and shows rough outlines for muscle-insertion. The latter are likewise present on the thick eygomatic arch. Attention may also be called at this point to the prominent processus marginalis on the posterior border of the malar bone. The processus anguli rnandibulae assumes in our case special interest, in as much as Herpin ('07) reported that this anomaly is rare in the negro and when present is poorly developed. The abnormal suture on the frontal bone, which is situated not exactly median but somewhat to the right, consists on its outer surface of a transverse, irregular, dentate part, 15 mni. long, and of two lateral, ascending limbs, which diverge upward and have a length of 9 and of 13 mm. on the right and on the left respectively. The distance between the upper ends of these diverging limbs is 23 mm. The middle of the transverse part is situated 25 mm. above the nasion arid 15 rnm. below the line con- necting the two tubcra frontalia. If, as according to Schwalbe ('01) the length of the frontal arc is represented as 100, thcn the transverse portion of the suture lies 20.3 above the nasion. It is of interest to compare the position of the abnormal suture on the frontal bone in the author's case with those reported by Schwalbe ('Ol), Fischer ('02) and Davida ('14). Table 1 is a compilation of the tables of the two first mentioned authors with the corresponding measurements of Davida's case and of that herein described. The figures show that the suture or fis- sure is always situated below the level of the tubertt frontalia, and with oiily two exceptions always in the upper half of the nasal third of the nasion-bregma arc. In thc twelve European skulls the average relative distance between the nasion and the 262 SDOLF H. SCHULTZ

TABLE 1 Positior~of the transverse abnormal suture on the mtal bone c adults ~ DISTANCE POSITION P THE SUTUI11 18 THB SUTURE FROM N>\aiox BELOW AUTHOR RACE IOE SEX v mil ~L&-T01 RTE:HT UBIHIL PHE FRONTAL LINT: IN ARC MILLIMETER8

European 32 y. 18.5 17.5 I European ad. 17.3 11.0 Sehwalbe ...... 1 European 31 y. 17.1 19.0 European 58 y. 20.3 19.5 I European 41 y. 13.8 20.0 f Europcan ad. 18.0 18.0 I European 64 y. 23.9 19.0 European 40 y. 22.2 20.0 European ad. 18.5 16.0 Fischer ...... European ad. 15.2 15.0 European 41 y. 20.0 29.0 European 19 y. 17.4 16.0

Negro ad. 27.5 12.0

I Negro ad. 21 .8 11 .o Davida...... ? 50 y. 15.4 SchuIta...... Negro 55 y. 20.3 15.0 suture is 18.8 mm., and the distance between the intertuberal line and the suture 18.3 mm. The average of the two negro skulls of Fischer and that of the author's case is, for the corresponding measurements, 23.2 and 12.6 mm. respectively. There- fore the suture in the negro seems to be relatively higher above the nasion and closer to the intertuberal line than in the white. The exact determination of the position of this abnormal suture is also of importance in the explanation of its origin, as will be seen later. Upon examining the inner surface of the skull, the suture is Iike- wise found to be extensive (fig. 3). Incidentally it might be stated that the crista frontalis interna is only moderately developed, as was the case in the skull with the same anomaly described by Rauber ('03). In two of Schwalbe's cases the crista frontalis was examined, and found in both to be broad and blunt. For the most part the abnormal suture on theinner surface communi- cates with that on the outer surface, often allowing the passage FONTANELLA METOPICA I&- AN SDULT SKULL 263

of a fine bristle. The transverse portion presents itself on the inner surface as eight, short perpendicular adjacent fissures, with a total width of 9 mm. and located 19 mm. above the foramen coecum. The lateral limbs of the suture, which also diverge upward, %restraight regular fissures, in contrast to those on the tabula extcrna. The right limb is 13, the left 19 mm. in length and they are 16 mm. apart at their upper ends. The bony part included by the suture is narrower but higher on its inner side than on the outer. On a horizontal section through the frontal

Fig. 3 Frontal bone of the skull in figure 2 seen from the inside (upper part sawed oft'). bone, at a level somewhat above the transverse portion of the abnormal suture, a trapezium is formed by the lateral limbs, with its shorter base directed inward. This wedge-shaped piece of bone is plainly shown in Rauber's section of a similar case. Schwalhe directed attention to the fact tlhat adult skulls showing remnants of a fontanella metopica present an unusually large interorbital breadth. Table 2 is a compilation of tables by Schwalbe and Fischer 51-ith Rauber's case and that of the author, in which the interorbital breadths and the interorbital indices are given. The interorbital index represents the relation between the interorbital breadth and the internal biorbital 264 ADOLF H. SCHULTZ

TABLE 2 Interorbital brcadlk and inlerorbilal index on adult skulls with the abnormal sulure wr Jssure on [lie frontal bone

UTERORBIT.4L XTERORBITAL lUTKOR RACE SEX BHEdDTH lNDhX

mm.

I European 28.5 26.6 I European 32.0 30.2 Gchwalk1e...... 1 European 27.5 27.5 European 28.0 26.4 European 31.0 29.8

European 31 .o 30.1 European 29.0 26.9 I European 29.0 26.6 Fischer...... i European 24.0 25.8 I European 30.0 29.4 Negro 26.0 26.3 Negro 37.0 33.3 Rauher ...... European 30.5 Schult,z...... Negro 32.0 29.1 breadth; the technique of these measurements may be found in Schwalbe’s studies on Pithecanthropus erectus (’99). In this same work are published similar measurements of a considerable nuniber of normal skulls of most heterogeneous races. Xccord- ing to these measurements, the interorbital breadth varies between 18 and 31 mm. with an average of 24.2 mm., the interorbital index lies between 20 and 30.1 with an average of 24.3. X comparison of these figures with table 2 shows that both the absolute and relative interorbital breadths of skulls showing remnants of a metopical fontanelle are much above the average. For the determination of the relative frequency of the anomaly in the two sexes, the material at our disposal has been much en- larged through the published cases of transverse fissures in the frontal bone of children aid newborns. In Scliwalbe’s cases sex is stated in 9 juvenile and in 5 adult; all were rriale except one newborn. Fischer found in 1 newborn and in 7 adults, in which sex was known, that the female sex was represented twice. FONTANELLA METOPICA IN AN ADULT SKULL 265

Adding to these the case of Rauber and that of the author, both of which were males, the total of males is 21, of females 3. The anomaly, therefore, would appear to be of much greater frequency in males. This same preponderance has been found by the author ('16) in another anomaly, namely, the persistent canalis cranio pharyngeus, and this relatively greater frequency has been likewise shown in respect to other anomalies. From this it would seem probable that anomalies are more common in the male, but whether this is a rule for progressive or for atavistic anomalies, or for both, can only be determined when care is taken by investigators to always mention the sex in reporting anomalies. Short transverse sutures or fissures occurring in the lower third of the frontal arc in adults have always been interpreted by the various authors as remnants of the fontanella metopica, but the origin of the latter has been explained in widely different ways. The inetopic fontanelle was first described by Gerdy in 1837. He was followed by Hamy and the Italian scientists Maggi, Riccardi, Staderini and Zanotti. Of these, Harny ('772) sees in the metopical foritanelle a divergence of the lines of ossification of the tubera frontalia. Maggi ('94, '98, '99) inter- prets the fontanella metopica as a product of the approximation of the four frontalia media. These assumptions are based upon his isolated comparative anatomical observations. Zanotti ('01) explains the medio-frontal fontanelle as the last trace of the foramen, which corresponds to the location of the paraphysis in primitive vertebrates; in other words, a foramen frontale for the paraphysis similar to the foramen parietale for the epiphysis. Both Maggi and Zanotti to a certain extent place atavistic in- terpretations upon the fontanelle, but these must be considered as extremely hypothetical. Bolk ('11) was led to believe that the fontanella metopica arises at the site of the primitive or primary nasofrontal suture. This opinion was based upon observations on monkeys, in which the nasal bones have become shortened, that is the supramaxil- lary portion of the nasalia is displaced by a medial growth of the frontalia, by which process a secondary naso-frontal suture, situated closer to the apertura nasalis, is formed. This theory 266 ADOLF H. SCHULTZ

does not explain in a satisfactory manner the extremely rare occurrence of a true metopic fontanelle in monkeys, together with the relatively frequent appearance of incomplete nasal reduction. On the other hand, the relative frequency of the metopic fontanelle in man according to Schwalbe is 15.2 per cent in children up to 1%years, whereas high reaching nasal bones, such as are found in monkeys, have never been described in the human skull. Moreover, it must be borne in mind that the remnants of the fontanella metopica are often situated in the adult high above the nasion. As shown in table 1, the lowest point of the remnants of the fontanelle is located as much as 27.5 per cent of the frontal arc above the nasion, its middle point, being even higher. If the fontanelle really corresponds to the original uppermost end of the nasalia, then the latter must have extended between the frontalia high above tlhe orbits and the superciliary ridges. Bolk assumes that the supranasal portion of the frontal suture (supranasal field or triangle)-a frequent finding in adults-is the resuIt of the reduction of the nasalia. However, this supranasal suture reaches as a rule only slightlyabove the glabella and not,, as Bolk supposes, to the level at which the fontanella metopica occurs. Rauber ('06) describes the skull of a child with two fontanelles at the frontal suture (fonticulus interfrontalis superior et inferior) which in his opinion had become separated from the frontal arm of the anterior fontanelle. The fonticulus interfrontalis inferior corresponds to the metopic fontanelle, and as a factor in its remaining patent Rauber considers it possible that the site of the anterior neuropore of the medullary canal of vertebrates exerts its influence under special circumstances, even to the ossification of the skull. Schwalbe ('01) in contrast to the explanations offered by pre- vious authors, considers it possible that the metopic fontanelle is to be conceived as a progressive variation, which bears a rela- tiori to the greater development of the frontal lobe of the cere- brum. The adult skull described in this paper would seem to support this theory inasmuch as its capacity was 1520 cc. and its smallest frontal width was 109 mm. Both these measurements are rather large for the negro; on the other hand Fischer's cases FONTANELLA METOPICA IN AN ilDULT SKULL 267

showed the metopic fontanelle to be present in two idiots, one of them a microcephalus with a skull capacity of only 704 cc. Schwalhe in his explanation makes use of the hypothetical sup- position that the tubera frontalia might consist of two adjacent ossification centers, which usually join immediately, but in ex- ceptional cases remain separate, later forming two independent systems of lines of ossification. The divergence of these lines forms the metopic fontanelle, which in children is situated on a plane with the tubcra frontalia. Schwalbe emphasizes the fact that the metopic fontanelle and its derivatives are always found at a definite location, while the fontanelles and fontanelle bones which arc found at timcs in the upper portion of the frontal suture have a more variable situation and are to be included in the great fontanelle. Schwalbc cites among other the cases described by Staderini, in which the fontanella metopica is connected with the great fontanelle by a wide space. In spite of this, however, he makes a distinction between the two above mentioned fontanelles, which rests purely upon the situation of the metopic fontanelle. According to Schwalbc in children up to 13 months the latter varies in respect to the lower end of the fontanelle from 5.6 to 17.8, in respect to its middle point from 11.2 to 22 per cent of the frontal arc above the nasion. Fischer described the skulls of two children in which interfrontal fontanelle bones are divided in two and in three part’s respectively. In one of these the middle point of the fontanelle bone was situated 30.6 in the other 50 per cent of the frontal arc above the nasion. It is evident that the position of the metopic fontanelle is not as definite as claimed by Schwalbe, who makes the following statement : In the rare cases in which two or wen three groups of Wormian bones occur in the frontal suture, only the lowest corresponds to the normal medio-frontal fontanelle; those situated near the parietal bones, however, are to be considered as Worrnian hones in an abnormally wide suture (hydrocephalus). The latter may even represent the anterior end of the large fontanelle, which has extended abnormally far into the frontal region. It sometimes occurs that the anterior end remains open for a longer period than that portion lying directly posteriorly; therefore the anterior end may become separatcd as a secondary fontanelle. 268 ADOLF 13 SCHULTZ

This dist'inction of Schwalbe seems somewhat arbitrary, inasmuch as all transitions can be observed in juvenile skulls. On the basis of original observations the author is convinced that the metopic fontanelle is derived from the bregmatic fontanelle, and at some time has become separated from it. Figure 4 gives the best proof. An interfrontal suture wide at its upper part, that is, a very long arm of the great fontanelle, as shown in num- bers 1, 2, 3 and 4 in figure 4 is not of rare occurrence. Among 35 skulls of infants up to a few months' old the frontal arm of the great fontanelle was found to extend six times to within 10 to 17

2. Negro newb.

?.White 7m. intrroufer.

6. Negro Sm. 8. White 4 m. 5.

Pig. 4 Normae frontales of frontal bones of juvenile skulls with a long arm of the bregmatic fontanelle, which has been constricted in the lower cases to form a metopic fontanelle. FONTANELLA METOPICA IN AN ADULT SKULL 269 mm. of the nasion. In three other cases the great fontanelle reached within 22 mm. of the nasion. This prolonged arm of t'he great fontanelle is an extreme variation, and is not necessarily a result of hydrocephalus. In the skull of a year old hydrocephalic negro, the author found thc great fontanelle reaching to within 16 mm. of the nasion; in contrast to the cases in figure 4, however, it was, even at its lower end, 17 mm. wide; in the middle of the frontal arc 29 mm. and at its upper end 35 mm. It is striking that the lowest portions of the frontal hones always approximate

Fig. 5 Norma verticalis of a skull of erethizon dorsatus with fontanelle bones. each other and indeed to a height which is considered typical for the position of the metopic fontanelle, that is, to a point to which the frontal arm of thc great fontanella may extend un- interrupted or constricted. As a designation for the lowest portion of such long bregniatic font8anelles extending into the nasal third of the frontal arc, the name fontanella metopica may well be retained. Howex-er, no fundamental difference is to be made between thc two nientioned fontanelles. Tt is more frequent for the lower end alone to remain patent in children and

THE AMERIC.4N JOURNAL OF ANATOMY, VOl,. 23, XO. 2 270 ADOLF 11. SCHULTZ to be recognizable in adults. The constriction of different portions of the frontal arm of the great fontanelle results from locally decreased or increased growth of the lines of ossification, and may occur in any situation, but appears to be most common between the two tubera frontalia. Double constriction to form secondary fontanelles has also been described (Rauber '06), This identity of the metopic and the great fontanelle is also demonstrated by the position of the fontanellebones, which occur anymhere from the bregma to the upper portion of the nasal third of the frontal arc (Hartmann 1868, Barclay-Smith '09 and '10, Gulliver 1890). Whether the above described case of partial persistence of the metopic fontanelle in an adult was associated with a fontanelle bone can not be determined with certainty, but seems probable, especially upon examining t'he inncr surface. Before any definite statements can be made as to the cause of the occurrence and partial persistence of a long frontal arm of the great fontanelle, more material must be available, and attention must be paid to correlations, especially in the frontal region. The author hopes by this contribution to stimulate interest in this anomaly in order that further cases may be reported. Observations on the occurrence of fontanelle structures in the frontal bones of mammals have been reported in a limited number, and further cases would be of great value. Among 10 skulls of erethizon dorsatus, which the author collected recently, 3 cases presented paired symmetrical fontanelle bones extending far between the frontalia. Figure 5 shows one of these cases. FONTANELLA METOPICA IN AN ADULT SKULL 271

BIRLTOGRAPIIY

BARCLAY-SMITH,E. 1909 A rare condit,ion of Wormian ossifications. Jour. of Anat. and Yhys., vol. 43, p. 277. 1910 Two cases of Worrnian bones in the bregmatic fontanelle. Jour. of Anat. and Phys., vol. 44, p. 312. BOLK,L. 1911 Die Herkunft tier Fontanellametopica bcim Mcnschcn. Anatom. Anzeiger, Bd. 38, Ergzh., p. 195. DAVIDA,E. 1914 Beitriige zur Persistene dcr transitorischen Niihte. Anatom. Anzeiger, Bd. 46, p. 399. FISCHER,E. 1902 Zur Kenntnis der Font.anella metopica und ihrer Bildungcn. Zeitschr. f. Morphol. und Anthrop., Bd. 4, p. 17. GERDP,J. V. 1837 Recherches ct propositions d’anat.ornie, dc pathologic et de tocologie, et,c. These de Paris, 1837, p. 6. GULLIVER,G. 1890 A skull with Wormian bones in the frontal sutiire. Jour. of Anat. and Phys., vol. 25. Proceedings of the Anatomical Society of Great Britain and Ireland, hTov. 1890. HAYY,E. 1872 Bicerche sulk fontanelle anomale del cranio umano. Archivio per I’antropol. e la ctnologia 11, p. 6. HARTMANN,G. 1869 Bcitriige eur Osteologie der Keageborenen. Diss. Tubingen. HEEPIN,1907 Evolution de 1’0s maxillaire inf6rieur. Thhe pour le doctorat dc m6di.cine. Paris. MAGOI,L. 1894 Preinterparietale e fontanella int,erparietale in un idrocefalo di Bos taurus juv. Rendiconti del Real Ist,ituto Lombardo., vol. 27, p. 160. 1898 Ornologie craniali fra Ittiosauri e feti dell’uomo e d’altri inammi- feri. Reridiconti del Real Ist’ituto Lombardo, vol. 31, p. 631. 1899 Ossicini metopiai negli uccelli e nei manimiferi. Rendiconti del Real 1stitut.o Lombardo, vol. 32. 1899 FontanelIc m6topiqiie et frontaux moyens quadruples chez les v6rt6brGs supdricurs. Archives ital. de biologie. T. 32, fasc. 3: p. 4.53. RAUBER,A. 1903 Zur Kcnntnis des 0sinterfrontale und supranasale. Anatom. Anecigcr. 22. Bd. p. 214. 1906 Fonticuli intcrfrontales inferior et superior. Gegenbaur’s Morpholog. Jahrbuch, Bd. 35, p. 354. RICCAEDI,P. 1878 Studii intorno Di crani Papuani. Archivio pcr I’antrop. e la etnol., 8, p. 25. SCHULTZ,,4. H. l9lG Der Canalis cranio-pharyngeus pcrsistens beim Mensch und bci dcn Men. Gegenbaur’s inorpholog. Jahrbuch, Bd. L, Heft 2. SCHWALHE, G. 1899 Studien tiller Pithecanthropus erectus Dubois. Zeitschr. f. Morphol. u. Anthrop., Btl. p. 16. 1901 Uebcr die Fontanella metopica (medio-frontalis) und ihre Bildungcn. Zeitschr. f. Morphol. u. hnthrop., Rd. 3, p. 93. STADERINI,R. 1896 Osservazioni anatomiche. 11. Tntorno alla fontartella medio-frontale del cranio iimano. Slti della R. ilccad. dei fisiocrit,ici. Siena. ZANOTTI,1901 La fontanella mctopica ed il suo significato. Bollettiiio Science hlcdiche, Bologna, 8, Ser. 1’. 2.