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Home , Mandible, Sphenoid bone, Zygomatic bone, Zygomatic process

Ossification Defects and Craniofacial Morphology In Incomplete Forms of Mandibulofacial Dysostosis

A Description of Two Dry

ERIK DAHL, D.D.S., DR. ODONT. ARNE BJORK, D.D.S., ODONT. DR. Copenhagen, Denmark

The morphology of two East Indian dry skulls exhibiting anomalies which were suggested to represent incomplete forms of mandibulofacial dysostosis is described. Obvious although minor anomalies were found localized to the temporal, sphenoid, the zygomatic, the maxillary and the mandibular . The observations substantiate the concept of the regional and bilateral nature of this malformation syndrome. Bilateral orbital deviations, of the malar bones, and incomplete zygomatic arches appear to be hard tissue aberrations which may be helpful in exami- nation for subclinical carrier status. Changes in mandibular morphology seem to be less distinguishing features in incomplete or abortive types of mandibulofacial dysostosis. KEY WORDS craniofacial problems, , mandibulofacial dysostosis, , sphenoid , ,

Mandibulofacial dysostosis (MFD) often roentgencephalometric examinations were results in the development of a characteristic made of the skulls, and tomograms were ob- facial disfigurement with considerable simi- tained of the internal and middle . Com- larity between affected individuals. However, parisons were made with normal adult skulls the symptoms may vary highly in respect to and with an adult exhibiting the char- type and degree, and both incomplete and acteristics of MFD. All of the skulls were from abortive forms of the syndrome have been the same ethnic group. ' reported in the literature (Franceschetti and Klein, 1949; Moss et al., 1964; Rogers, 1964). Results In previous papers, we have shown the DEsCRIPTION OF THE SKULLS. The overall additional information about skeletal aber- size of both skulls was considered to be within rations which can be obtained from studies of normal limits for their ethnic group. The dry skulls exhibiting various pathological con- deviations in both specimens were localized ditions (Dahl, 1971; Dahl et al., 1975). Also, to the temporal, sphenoid, and zygomatic in the identification of incomplete forms of a bones, the maxilla, and the mandible. Only given syndrome, the detailed information of these bones will be described in detail. the bony changes provided by such studies Skull No. 177-The squamous part of the may be helpful and may direct clinical atten- temporal bone is extended forward on both tion to areas where problems can be antici- sides and forms the major part of the bottom pated. The present report describes two skulls of the temporal which appears more in which minor symptoms of mandibulofacial narrow than normal (Figure 1). The petrous dysostosis were present. and tympanic parts of the temporal bones appear normal whereas the zygomatic Materials and Methods is hypoplastic on both sides with a consequent The two skulls examined were those of lack of continuity of the zygomatic arches. young adults of East Indian ancestry. No sex The greater wings of the are determination was attempted. Clinical and grossly underdeveloped, and the pterygoid processes are narrow and thin (Figure 2). The authors are affiliated with the Royal Dental Otherwise, this bone is normal. The temporal College, Copenhagen, Denmark. process of the zygomatic bone appears on 83 SKULL NO. 177

"Tig FIGURE 2 a and b. Close-up of the temporal and on the right and the left sides.

FIGURE 3. Frontal view. FIGURE 4. The mandible. Dahl and Bjork, manpiBuLOFACIAL DysOSTOSIS 85

SKULL NO. 65

FIGURE 5 a and b. Lateral views of skull both sides as a hypoplastic blind-ending ex- and length. The entire anterior surface ap- tension leaving a gap of 1.5 cm between it pears markedly concave and the teeth facially and the abortive of the inclined. The zygomatic processes are ex- temporal bone. The zygomatic bone on both tended laterally forming one half to two thirds sides forms only the lateral part of the down- of the inferior orbital margins. ward, lateral inclining inferior orbital margin. The mandible appears as a slender sym- Thus, the zygomatico-maxillary sutures are metrical bone with reduced height of the placed lateral to the corpus and of the anteroposterior width of the (Figure 3). The lateral orbital margin lies far ramus. The mandibular are rela- back in the , and irregularities are seen in tively small. On both sides, small exostoses the upper part of the frontosphenoid process are seen on the lateral aspect of the condylar on the left side. (Figure 4). The maxilla is reduced in height, width, Skull No. 65-The squamous part of the

FIGURE 6 a and b. Close-up of the temporal and infratemporal fossa on the right and the left sides.

86 Cleft Palate Journal, April 1981, Vol. 18 No. 2

SKULL NO. 65

FIGURE 7. Frontal view.

FIGURE 8 a and b. Close-ups of the orbits. temporal bone is bilaterally small, and the The pterygoid processes are small and end articulation with the greater wing of the very high on the posterior aspects of the max- sphenoid is irregularly shaped on the left side illa (Figure 6). The corpus of the zygomatic (Figure 5). The zygomatic processes are defi- bone is small on both sides and both the cient and are not fused to the zygomatic bone. temporal and the frontosphenoid processes The temporal surface of the greater wing of are hypoplastic. The lateral orbital margin the sphenoid bone is small bilaterally, and lies far back, and its middle third is formed supernumerary suture lines are seen on the by a serrated area at the articulation between right side. The infratemporal surface is de- the zygomatic and the frontal bones (Figure markated from the temporal surface by a crest 8). Atypical supernumerary sutures are also and appears deficient - especially on the right seen in the lateral orbital wall. The anterior side, and supernumerary suture lines are seen. surface of the maxilla exhibits some concavity

Dahl and Bjork, manpmsuroractar pysostosts 87 corresponding to the , but otherwise the maxilla is well developed in all dimen- sions. The zygomatic processes are large and laterally extended forming two thirds of the downward and outward sloping inferior mar- gins of the orbits (Figures 7 and 8). In this specimen, the mandible deviated less morphologically than did skull No. 177. The ramus, however, was relatively thin and was narrow in the anteroposterior dimension. The condyles appeared to be of normal shape and size (Figure 9). The coronoid processes are thin, and their upper margin appears on both sides as a horizontal edge. RoENTGENCEPHALOMETRIC EXAMINATION. Roentgencephalometric films were obtained from both skulls (Figures 10 and 11). Skull No. 177 is characterized by a large FIGURE 11. Lateral roentgencephalometric film of bimaxillary alveolar and in- skull No. 65. creased facial inclination of the incisors both in the maxilla and in the mandible. The lateral orbital margin is placed far back in the face. The mandible is retrognathic and in- clined backward but otherwise appears mor- phologically normal. In skull No. 65, the alveolar prognathism in the maxilla is increased and the upper incisors facially inclined. The mandible is re- trognathic relative to the cranial base and backward inclined. Otherwise, the contour of the mandible appears normal. The lateral margin of the is placed far back in the face.

FIGURE 12. Superimposition of roentgencephalo- metric tracings of previously described skull (No. 110) with complete MFD (full line) and skull No. 177 (dotted line).

In Figure 12, a cephalometric tracing of skull No. 177 is superimposed on the tracing of the previously described skull exhibiting the characteristics of MFD (Dahl et al., 1975). The facial contour is essentially the same FIGURE 10. Lateral roentgencephalometric film of except for the less deviating morphology of skull No. 177. the mandible in skull No. 177. Comparison of

88 Cleft Palate Journal, April 1981, Vol. 18 No. 2

report exhibited obvious, although minor, os-

sification anomalies which had much in com-

mon with the bony aberrations seen in MFD.

The issue is, therefore, do these specimens

represent incomplete forms of MFD? Diag- ~ ~ ~ -~ ~ _- nosis of any syndrome in which some of its

features are not expressed may be a problem

especially in sporadic occurrence, and the eti-

ologic background for the malformations seen

=- _ h in the skulls was unknown. However, detailed A \ FS bessc- 7 <1 _L i\ *}_| Q e / / I \ \\ / comparison between the observed anomalies ~ \ 40 /

\ l” a 70 Z \ ~ / P \ t ~Lee. I /_/ and the bony changes previously described in i / ~ tS I‘ \ / 20d uP 3 ~ = 7 \\ } a ll *_l_ t specimens representing complete MFD (Dahl 1 / A 1 \ / \ \ /. \ me- Leet, 1 et al., 1975; Herring et al., 1979) showed a #7 r z- "ae <- \ {\ high degree of similarity both with respect to

type and localization. MFD is characterized

by bilateral occurrence of the anomalies, and

the involvement in both of these skulls was

similar on the right and left sides, although

the two sides were not completely symmetri-

cal. The skulls differed from the complete

form of MFD in that there was no involve-

ment of the external auditory canal; there FIGURE 13. Superimposition of roentgencephalo-

metric tracing of skull No. 177 (dotted line) and skull No. were no ossicular defects; the deficiency of the

65 (full line). zygomatic bones was mild; and mandibular

changes were minor.

Incomplete and abortive forms of MFD the cephalometric tracings of skull No. 177 have previously been described in clinical and skull No. 65 is shown in Figure 13. Com- cases with deformities, downward and mon features in these skulls were the mandib- outward inclining palpebral fissures, and un- ular retrognathia and the backward position derdevelopment of the malar bones as the of the lateral orbital margin. The differences major clinical features (Berry, 1889; Isakow- in the contours of the cranial vault in the itz, 1927; Franceschetti and Klein, 1949; Zu- frontal and the occipital regions as well as the nin, 1957; Moss et al., 1964). No reports of larger mandible in skull No. 65 could only the subsurface anatomy of this condition have partly be explained by the difference in the been published. The bony anomalies observed size of the two skulls. in the two skulls reported here appear to agree

Tomograms of the middle and internal ear with clinical findings. In both skulls, the orbits revealed no abnormalities in either of the were relatively large. Their downward-out- skulls. ward obliquity, as well as the deficient and

backward placed lateral orbital margins, con- Discussion tribute to the understanding of clinical fea-

Comprehensive knowledge of the pheno- tures that have been found. typical spectrum of a given syndrome is nec- Because of the overall pattern of abnor- essary for correct delineation of the condition. malities in the two specimens presented here,

Although minor anomalies may not be of it was presumed that they represented incom- immediate surgical or medical significance, plete forms of MFD. the finding of such anomalies may add infor- Changes in mandibular morphology have mation about the clinical features of the syn- been considered to be essential to the diag- drome and may help to improve genetic coun- nosis of complete MFD (Pruzansky, 1969; selling. This is especially important when the Roberts et al., 1975; Behrents et al., 1977). In recurrence risk is high and the disorder disfig- both of the skulls in the present study, the uring as is often the case with MFD. mandible was retrognathic and appeared as

Both of the specimens presented in this a slender bone. Minor deviations were seen in Dahl and Bjork, MaNDIBULOFACIAL DYSOSTOSIS 89 the condylar and coronoid processes, but cleft and palate, Tandlaegebladet, 75, 1170-1181, otherwise the appeared morpho- 1971. Dahl, E., Kreiborg, S. and Bjork, A., A morphologic logically normal. The observations suggest description of a dry skull with mandibulofacial dysos- that the changes in mandibular morphology tosis, Scand. J. Dent. Res., 83, 257-266, 1975. characteristic of complete forms of MFD may Franceschetti, A., and Klein, D., The mandibulo-facial be less distinguishing in incomplete or abor- dysostosis, a new hereditary syndrome, Acta Ophthal- mol., 27, 141-224, 1949. tive types of the syndrome. The explanation Herring, S. W., Rowlatt, U. F. and Pruzansky, S., Ana- may be that the original damage has been less tomical abnormalities in mandibulofacial dysostosis, extensive with minor involvement of the man- Am. J. Med. Genet., 3, 225-259, 1979. dibular condyles. Furthermore, the functional Isakowitz, J., Eine seltene erbliche Anomalie der Lid- environments influencing mandibular mor- spalte (atypisches Lidkoloboma?), Kiin. Monatsbl. Au- genheilkd., 78, 509-512, 1927. phology during growth have been less deviat- Moss, M. H., Saphir, R. L., and Gottlieb, M. I., Mandi- ing. bulofacial dysostosis, Am. J. Dis. Child., 107, 304-307, Bilateral orbital deviations, hypoplasia of 1964. the malar bones, and incomplete zygomatic Pruzansky, S., Not all dwarfed mandibles are alike, Pro- ceeding of First Conference on Cilinical Delineation of arches seem to be hard tissue defects which Birth Defects, Part 2, Malformation Syndromes in may serve as diagnostic aids in the clinical Birth Defects, Original Article Series, D. Bergsma (ed.), identification of incomplete types of MFD. New York: National Foundation, Vol. 2, 120-129, 1969. Roberts, F. G., Pruzansky, S., and Aduss, H., An x- References radiocephalometric study of mandibulofacial dysosto- Behrents, R. G., McNamara, J. A. and Avery, J. K., sis in man, Arch. Oral Biol., 20, 265-281, 1975. Prenatal mandibulofacial dysostosis (Treacher Collins Rogers, B. O., Berry-Treacher Collins syndrome: A re- syndrome), Cleft Palate J., 14, 13-34, 1977. view of 200 cases, Br. J. Plast. Surg., 17, 109-137, 1964. Berry, G. A., Note on a congenital defect (? coloboma) of Zunin, C., Contributo allo studio della sindrome de the lower lid, R. London Ophthalmol. Hosp. Rep., 12, 255- Franceschetti. Rilievi clinici e genetici da una osser- 257, 1889. vazione familiare, Acta Genet. Med. Gemello. (Roma), 6. Dahl, E., Craniofacial structures in a skull with bilateral 483-491, 1957.