Ossification Defects and Craniofacial Morphology In Incomplete Forms of Mandibulofacial Dysostosis A Description of Two Dry Skulls 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 ossification anomalies were found localized to the temporal, sphenoid, the zygomatic, the maxillary and the mandibular bones. The observations substantiate the concept of the regional and bilateral nature of this malformation syndrome. Bilateral orbital deviations, hypoplasia 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, mandible, mandibulofacial dysostosis, maxilla, sphenoid bone, temporal bone, zygomatic bone 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 ear. 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 skull 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 fossa 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 process 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 sphenoid bone 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 infratemporal fossa 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 zygomatic process 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 infraorbital foramen corpus and of the anteroposterior width of the (Figure 3). The lateral orbital margin lies far ramus. The mandibular condyles are rela- back in the face, 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. heads (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 incisors, 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 prognathism 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 orbit 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 eyelid 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.