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Radiographic features of the ear-related developmental anomalies in patients with mandibulofacial dysostosis
lnternationalJournalofPediatricOtorhinolaryngology, 7 (1984) 229-238
229
Elsevier PER00253
Radiographic features of the ear-related developmental anomalies in patients with mandibulofacial dysostosis * M a h m o o d F. Mafee 1, Joyce A. Schild z, A. K u m a r 2, G.E. Valvassori ~ and Samuel Pruzansky Departments of I Radiology and " Otolaryngology- Head and Neck Surgery, University of lllinois College of Medicine and University of Illinois Hospital and Eye and Ear Infirmary, Chicago, IL (U.S.A.) (Received January 6th, 1984) (Revised March 20th, 1984) (Accepted March 26th, 1984)
Key words: branchial arches - mandibulofacial dysostosis - Treacher Collins syndrome - HallermannStreiff syndrome
Summary Among the conditions that arise from disturbances in development of the first two branchial arches, the symmetric syndrome of mandibulofacial dysostosis and the asymmetric anomalies of the hemicraniofacial microsomia represent a characteristic pattern of craniofacial malformation distinct from other first and second arch syndromes. Since the usual embryonic aberration in both of these anomalies involves the first and second branchial arch derivatives, malformations of the external and middle ear are common. The external auditory canal is absent in the vast majority of the cases. Incudomallear deformities are usually present. In this paper, radiographic analysis of the ear-related developmental anomalies of 17 patients with mandibulofacial dysostosis is described.
Introduction The major deformities of the first and second branchial arch derivatives are generally grouped as symmetric and asymmetric [11,12]. Most of the congenital * Presented paper, SENTAC Annual Meeting, Orlando, FL, Dec. 4, 1981.
Correspondence and reprint requests: M.H Mafee, University of Illinois Hospital, Eye and Ear Infirmary, 1855 West Taylor Street, Chicago, IL 60612, U.S.A. 0165-5876/84/$03.00 © 1984 Elsevier Science Publishers B.V.
230 symmetric malformations affecting the first and second branchial arch derivatives have a genetic basis [4,12] and the degree of expression and abnormality frequently vary among individuals and among siblings with the same etiologic syndrome [12]. In studying the spectrum of the malformation syndrome, many patients may be found in whom facial morphogenesis is almost normal [12]. The malformations such as the similar syndromes of Treacher Collins and Hallermann-Streiff represent the symmetric patterns of malformation of severe effect [4,11,12]. Symmetric deformity of the face may also be acquired, particularly when it follows juvenile rheumatoid (Still's) disease of the temporomandibular joints with subsequent ankylosis of the joints [12,13].
Mandibulofacial dysostosis Mandibulofacial dysostosis (Treacher Collins syndrome) is a well-known malformation that affects the face, orbits, and ears bilaterally. Several comprehensive reports have described the features of this congenital malformation [1-5,9]. It is transmitted as an autosomal dominant trait, although many cases occur as spontaneous mutations [13]. In mandibulofacial dysostosis, the phenotypic characteristics that define the syndrome include mandibular hypoplasia (Fig. 1), malar hypoplasia, antimongoloid obliquity of the palpebral fissures, anomaly of the lower lid, coloboma a n d / o r malformations of the eyelashes, obliteration of the nasal frontal angle, and microtia. The rami of the mandible are hypoplastic, the angle of the mandible is
•
!
• ,-.'. 7
Fig. 1. A. Mandibulofacial dysostosis. B. Lateral skull. Note characteristic bowing of the lower border of the mandible. This peculiar downward curve of the horizontal portion of the ramus of the mandible is pathognomonic of this syndrome. Note hypoplastic acellular mastoids with absent external auditory canals. Note constriction of the air outlined pharynx particularly at the level of the oropharynx.
231 obtuse, and the lower border of the mandible is peculiarly concave, resulting in a deformed curve of the horizontal ramus (Fig. 1). Characteristically in this syndrome, the pharyngeal airway is hypoplastic (Fig. 1) [14].
Subjects To assess the otological malformations characteristic of mandibulofacial dysostosis the tomographic studies of 17 patients (34 ears) with a diagnosis of mandibulofacial dysostosis were reviewed. There were 10 female and 7 male patients with ages ranging from 1 to 31 years at the time of the study.
Results The external auditory canal was absent in 23 ears, severely hypoplastic in 6, and mildly hypoplastic in 5 (Table I). The tympanic cavity was absent in 12 ears, markedly hypoplastic in 14, and mildly hypoplastic in 7 ears. In one ear the tympanic cavity was considered near-normal (Table II). In 23 ears with absent external auditory canal, the middle ear cavities were closed by a thick osseous atretic plate in 18 and moderately thick atretic plates were noticed in the remaining 5. In the 6 ears with severely hypoplastic external auditory canals, the middle ear cavity was closed with a thick atretic plate in one ear; there were moderately thick osseous
TABLE I DEVELOPMENT OF THE EXTERNAL AUDITORY CANAL AND ITS RELATIONSHIP WITH THE ATRETIC PLATE IN MFD (34 EARS) No.
External auditory canal
No atretic plate
Thin atretic plate
0 5 6 23
normal mildly stenotic severely stenotic absent
0 2 0 0
0 1 1 0
Mod. thick atretic plate
Very thick atretic plate
0 2 4 5
0 0 1 18
TABLE II DEVELOPMENT OF THE MIDDLE EAR CAVITY IN MFD (34 EARS) Tympanic cavity Tympanic cavity proper Epitympanum
Normal or near n o r m a l
Mildly hypoplastic
Markedly hypoplastic
Absent
1 1
7 5
14 16
12 12
232 T A B L E III D E V E L O P M E N T O F T H E M A L L E U S A N D I N C U S IN M F D (34 EARS) Normal
Mildly hypoplastic
2
2
Markedly dysplastic (rudimentary) 7
Conglomerate incudomallear mass 7
Absence of incus and malleus 16
Fusion to atretic plate 7
atretic plates in 4 ears, and one showed a thin atretic plate (Table I). In 5 ears with mildly hypoplastic external auditory canals, two showed a moderately thick atretic plate, one showed a thin atretic plate, and two ears showed no atretic plate (Table I).
Ossicles The malleus and incus were absent (Fig. 2) in 16 ears (Table III). In 7 ears markedly dysplastic and rudimentary ossicles (Fig. 3) were recognized in the hypoplastic epitympanum (Table III). In 7 ears a single large conglomerate incudomallear mass was attached (Fig. 4) to the atretic plate or epitympanum or both (Table III). If otologic surgery is contemplated, in the presence of atretic plate, the incudomallear mass is most likely to be fused to the plate [8].
Mastoid, mastoid antrum, tegmen tympanum In 8 ears the mastoid was moderately hypoplastic with a few mastoid-air cells (Table IV). The mastoid was markedly hypoplastic or absent in 23 ears (Table IV). The mastoid was considered normal in 3 ears. The mastoid antrum was normal in 5
Fig. 2. Mandibulofacial dysostosis. Frontal tomogram of both temporal bones. Note agenesis of both external auditory canals, with a moderately thick atretic plate on the right and a very thick one on the left. Both tympanic cavities are hypoplastic, and no ossicles are recognized. The upper arrow points to the petrous portion of the fight facial nerve canal and the lower arrow points to its mastoid portion, which is short, superficial, and anterior in location.
233
Fig. 3. Mandibulofacial dysostosis. Frontal tomogram of the temporal bones. Note absence of the right external auditory canal and severely dysplastic left external auditory canal. The tympanic cavity on the right side is almost absent, and on the left side is severely hypoplastic. Note bilateral thick atretic plates, agenesis of the ossicles on the right and rudimentary ossicles on the left (arrow).
Fig. 4. Mandibulofacial dysostosis. Frontal tomogram of the left temporal bone. Note absence of the external auditory canal, thick atretic plate (3) and abnormal conglomerate ossicular mass (1) which is fused to the atretic plate (3). The lateral wall of the attic (2) is normal and the epitympanum is mildly hypoplastic.
234 TABLE IV DEVELOPMENT OF THE MASTOID AIR CELLS, MASTOID ANTRUM AND THE POSITION OF THE TEGMEN IN MFD (34 EARS) Normal Mod.hypoplastic Mar. hypoplastic Normal Hypoplastic Absent mastoid mastoid with few or absent mastoid antrum antrum antrum air cells 3 8 23 5 11 18
Low Normal lying tegmen tegmen 15 19
ears, hypoplastic in 11, a n d a b s e n t in 18 ears (Table IV). Five of the m a r k e d hypoplastic mastoids showed a hypoplastic a n t r u m , a n d in the r e m a i n d e r the a n t r u m was absent. T h e tegmen level was considered low (Fig. 5) in 15 ears a n d n o r m a l in 19 ears. The position of the tegmen is i m p o r t a n t when surgical correction of congenital aural atresia is contemplated. A n extremely low-lying tegmen makes surgical correction very difficult.
Fig. 5. Mandibulofacial dysostosis. Frontal tomogram of the left temporal bone. Note normal vestibule, lateral and superior semicircular canal, and internal auditory canal. The mastoid antrum is absent, and the tegmen tympani is low in position (upper arrows). Note also the thick atretic plate (1), and the entire vertical segment of the facial nerve canal (lower arrows), which is superficial laterally because of hypoplastic and rather flat mastoid.
235
Fig. 6. Mandibulofacial dysostosis. Frontal tomograms of the left temporal bone. The external auditory canal is almost near normal in size, but is closed medially by a thick atretic plate (2). Note moderately bypoplastic tympanic cavity (3), a short lateral wall of the attic (1), and dysplastic ossicles in the hypoplastic attic.
236 Facial nerve canal
The course of the facial nerve canal was normal in 12 ears. In 11 ears the tympanic and vertical segments of the facial nerve canal could not be properly assessed in the tomograms. In 11 ears the vertical portion showed a C-shaped configuration and was more anterior and superficial than normal. In one ear its labyrinthine portion was somewhat Prominent, and its vertical segment was very superficial (Figs. 2, 5).
Inner ear
In mandibulofacial dysostosis, an abnormality of the inner ear is rare and is considered an incidental finding. The cochleas, vestibules, semicircular canals, and internal auditory canals were normal in all 34 ears. The oval window was considered tomographically closed in 4 and normal in 30 ears. The round window was normal in all 34 ears. The cochlear duct was normally visualized in 22 ears and indeterminate in 12 ears. Although no tomographic projections were obtained to visualize the vestibular aqueduct, in 9 ears its course was indentifiable and normal. The carotid canals, jugular fossa, occipital condyles, and hypoglossal canals were normally identifiable in the tomograms. The temporomandibular fossa and the condyle were considered markedly hypoplastic in 26 ears and slightly hypoplastic to nearnormal in 8 ears.
Discussion
In the serial examination of the phenocopy of mandibulofacial dysostosis induced in the rat by the teratogen vitamin A, microscopic study of the induced ear defects revealed that the animal model was closely comparable in all respects to human mandibulofacial dysostosis [11]. The ear cartilages were irregular and reduced in size in experimental animals. The middle ear cavities were small, and there were irregularities in the shape, size, and number of the auditory ossicles. While the middle ear abnormalities were closely comparable on the two sides, there were small differences observed in some instances [11]. Dissection of the middle ear in cases of mandibulofacial dysostosis revealed the same minor discrepancies that are seen in the animal model [11]. The usual embryologic aberration in mandibulofacial dysostosis primarily involves first and second branchial arch derivatives. Therefore, congenital anomalies of the sound-conducting alrparatus in the external and middle ear are the characteristic otologic findings in this syndrome. Abnormalities of the inner ear structures of ectodermal origin theoretically are rare in this syndrome. The external ear is frequently abnormal in shape, size, and position. Extra rudimentary ear tags and blind fistulas may be observed in the same locality. Although patients with this syndrome have been described in whom no deformity of the auricle was present, when microtia is present it is most often symmetric [8].
237 Hutchinson et al. [8] noted symmetric deformities of the external ear in 13 of 16 patients with mandibulofacial dysostosis. Nine of them had grade 1 microtia. Microtia is most often mild (grade 1), but the severity of the hearing loss cannot be predicted exactly on the basis of auricular deformity. In other words, a relative but not absolute relationship is found between the microtia and the external ear canal and middle ear structures. Characteristically in mandibulofacial dysostosis the external auditory canal is most often absent (Fig. 2, 3) or may be hypoplastic (Fig. 3). Occasionally a near-normal external auditory canal may be seen only in those with grade 1 microtia. T h e middle ear cavity in mandibulofacial dysostosis is usually severely deformed. Agenesis of the middle ear cleft is not infrequent (Fig. 3). In the majority of the cases the middle ear cleft is hypoplastic and is closed by an atretic plate (Fig. 2). The bony external auditory canal arises from a solid core of epithelial cells which splits first in its deepest portion to form the outer surface of the tympanic membrane and then canalizes laterally [8]. The atretic plate is the primitive tympanic membrane which may be totally osseous or partially differentiated into a rudimentary tympanic membrane depending upon when developmental arrest occurs (Figs. 2, 3 and 6). Since the embryologic aberration in mandibulofacial dysostosis primarily involves the first and second branchial arch derivatives, deformities of the ossicles are almost always present. Agenesis of the incus and malleus is frequent (Figs. 2 and 3); often they are rudimentary (Figs. 3 and 6). Usually they form a conglomerate bony mass which is fused to the atretic place, the epitympanum, or both (Fig. 4). The stapes, a second branchial arch derivative, is malformed, rudimentary, or absent. Numerous authors have reported abnormalities of the stapes [6,7]. Although the stapes cannot be assessed properly with polydirectional tomogram, stapedial malformations are also common [8]. In the majority of cases, the mastoid and mastoid antrum are either poorly developed or absent (Fig. 5). The tegmen level may be low in position (Fig. 5). The course of the facial nerve canal may be normal; however, the facial nerve may pursue an abnormal course and is located more anteriorly than would be expected (Figs. 2 and 5). Since the membranous labyrinth derives from the ectodermal otocyst and develops independently from the remainder of the ear, which is primarily derived from the branchial apparatus, combined malformations of the inner, middle, and outer ear do not occur frequently [10]. References 1 Axelsson, A., Brolin, 1., Engstrom, H. and Linden, G., Dysostosis mandibulofacialis,J. Laryng., 87 (1963) 575-592. 2 Falzone,S. and Pruzansky,S., Cleft palate and congenital palatopharyngealincompetencyin mandibulofacial dysostosis: frequencyand problems in treatment, Cleft Palate J., 13 (1976) 354-360. 3 Francheschetti,A. and Klein, D., The mandibulofacialdysostosis, a new hereditary syndrome, Acta ophtbal., 27 (1949) 141-224. 4 Gorlin, R.J., Pindborg, J.J.°and Cohem, M.M. Jr., Syndromes of the Head and Neck (2nd edn.), McGraw-Hill, New York, 1976.
238 5 Harrison, S.H., Treacher Collins syndrome, Brit. J. plast. Surg., 3 (1951) 282-290. 6 Herring, S.W., Rowlat, U.F. and Pruzansky, S., Anatomical abnormalities in mandibulofacial dysostosis, Amer. J. reed. Genet., 3 (1979) 225-259. 7 Holbrow, C.A., Deafness and the Treacher Collins syndrome, J. Laryng., 75 (1961) 978-984. 8 Hutchinson, J.C. Jr., Caldarelli, D.D., Valvassori, G.E., Pruzansky, S. and Parris, P.J., The otologlc manifestation or mandibulofacial dysostosis, Otolaryng. Trans., 84 (1977) 520-528. 9 McKenzie, J. and Craig, J., Mandibulofacial dysostosis (Treacher Collins syndrome), Arch. Dis. Childh., 36 (1955) 391-395. 10 Neurmann, Y., Congenital mlcrotia and meatal atresia, Arch. Otolaryng., 66 (1957) 443. 11 Poswillo, D., The pathogenesis of the Treacher Collins syndrome (mandibulofacial dysostosis), Brit. J. oral Surg., 18 (1976) 1-26. 12 Poswillo, D., Etiology and pathogenesis of first and second branchial arch defects: the contribution of animal studies. In: J.M. Converse, J.G. McCarthy and D.M. Smith (Eds.), Symposium on Diagnosis and Treatment of Craniofacial Anomalies, Mosby, St. Louis, 1976, pp. 86-99. 13 Pruzansky, S., The temporomandibular joint. Otolaryng. clin. North Amer., 6 (1973) 523-548. 14 Shprintzen, R.J., Croft, C., Berkman, M.D. and Rakoff, S.J., Pharyngeal hypoplasia in Treacher Collins syndrome, Arch. Otolaryng., 105 (1979) 127-131.
229
Elsevier PER00253
Radiographic features of the ear-related developmental anomalies in patients with mandibulofacial dysostosis * M a h m o o d F. Mafee 1, Joyce A. Schild z, A. K u m a r 2, G.E. Valvassori ~ and Samuel Pruzansky Departments of I Radiology and " Otolaryngology- Head and Neck Surgery, University of lllinois College of Medicine and University of Illinois Hospital and Eye and Ear Infirmary, Chicago, IL (U.S.A.) (Received January 6th, 1984) (Revised March 20th, 1984) (Accepted March 26th, 1984)
Key words: branchial arches - mandibulofacial dysostosis - Treacher Collins syndrome - HallermannStreiff syndrome
Summary Among the conditions that arise from disturbances in development of the first two branchial arches, the symmetric syndrome of mandibulofacial dysostosis and the asymmetric anomalies of the hemicraniofacial microsomia represent a characteristic pattern of craniofacial malformation distinct from other first and second arch syndromes. Since the usual embryonic aberration in both of these anomalies involves the first and second branchial arch derivatives, malformations of the external and middle ear are common. The external auditory canal is absent in the vast majority of the cases. Incudomallear deformities are usually present. In this paper, radiographic analysis of the ear-related developmental anomalies of 17 patients with mandibulofacial dysostosis is described.
Introduction The major deformities of the first and second branchial arch derivatives are generally grouped as symmetric and asymmetric [11,12]. Most of the congenital * Presented paper, SENTAC Annual Meeting, Orlando, FL, Dec. 4, 1981.
Correspondence and reprint requests: M.H Mafee, University of Illinois Hospital, Eye and Ear Infirmary, 1855 West Taylor Street, Chicago, IL 60612, U.S.A. 0165-5876/84/$03.00 © 1984 Elsevier Science Publishers B.V.
230 symmetric malformations affecting the first and second branchial arch derivatives have a genetic basis [4,12] and the degree of expression and abnormality frequently vary among individuals and among siblings with the same etiologic syndrome [12]. In studying the spectrum of the malformation syndrome, many patients may be found in whom facial morphogenesis is almost normal [12]. The malformations such as the similar syndromes of Treacher Collins and Hallermann-Streiff represent the symmetric patterns of malformation of severe effect [4,11,12]. Symmetric deformity of the face may also be acquired, particularly when it follows juvenile rheumatoid (Still's) disease of the temporomandibular joints with subsequent ankylosis of the joints [12,13].
Mandibulofacial dysostosis Mandibulofacial dysostosis (Treacher Collins syndrome) is a well-known malformation that affects the face, orbits, and ears bilaterally. Several comprehensive reports have described the features of this congenital malformation [1-5,9]. It is transmitted as an autosomal dominant trait, although many cases occur as spontaneous mutations [13]. In mandibulofacial dysostosis, the phenotypic characteristics that define the syndrome include mandibular hypoplasia (Fig. 1), malar hypoplasia, antimongoloid obliquity of the palpebral fissures, anomaly of the lower lid, coloboma a n d / o r malformations of the eyelashes, obliteration of the nasal frontal angle, and microtia. The rami of the mandible are hypoplastic, the angle of the mandible is
•
!
• ,-.'. 7
Fig. 1. A. Mandibulofacial dysostosis. B. Lateral skull. Note characteristic bowing of the lower border of the mandible. This peculiar downward curve of the horizontal portion of the ramus of the mandible is pathognomonic of this syndrome. Note hypoplastic acellular mastoids with absent external auditory canals. Note constriction of the air outlined pharynx particularly at the level of the oropharynx.
231 obtuse, and the lower border of the mandible is peculiarly concave, resulting in a deformed curve of the horizontal ramus (Fig. 1). Characteristically in this syndrome, the pharyngeal airway is hypoplastic (Fig. 1) [14].
Subjects To assess the otological malformations characteristic of mandibulofacial dysostosis the tomographic studies of 17 patients (34 ears) with a diagnosis of mandibulofacial dysostosis were reviewed. There were 10 female and 7 male patients with ages ranging from 1 to 31 years at the time of the study.
Results The external auditory canal was absent in 23 ears, severely hypoplastic in 6, and mildly hypoplastic in 5 (Table I). The tympanic cavity was absent in 12 ears, markedly hypoplastic in 14, and mildly hypoplastic in 7 ears. In one ear the tympanic cavity was considered near-normal (Table II). In 23 ears with absent external auditory canal, the middle ear cavities were closed by a thick osseous atretic plate in 18 and moderately thick atretic plates were noticed in the remaining 5. In the 6 ears with severely hypoplastic external auditory canals, the middle ear cavity was closed with a thick atretic plate in one ear; there were moderately thick osseous
TABLE I DEVELOPMENT OF THE EXTERNAL AUDITORY CANAL AND ITS RELATIONSHIP WITH THE ATRETIC PLATE IN MFD (34 EARS) No.
External auditory canal
No atretic plate
Thin atretic plate
0 5 6 23
normal mildly stenotic severely stenotic absent
0 2 0 0
0 1 1 0
Mod. thick atretic plate
Very thick atretic plate
0 2 4 5
0 0 1 18
TABLE II DEVELOPMENT OF THE MIDDLE EAR CAVITY IN MFD (34 EARS) Tympanic cavity Tympanic cavity proper Epitympanum
Normal or near n o r m a l
Mildly hypoplastic
Markedly hypoplastic
Absent
1 1
7 5
14 16
12 12
232 T A B L E III D E V E L O P M E N T O F T H E M A L L E U S A N D I N C U S IN M F D (34 EARS) Normal
Mildly hypoplastic
2
2
Markedly dysplastic (rudimentary) 7
Conglomerate incudomallear mass 7
Absence of incus and malleus 16
Fusion to atretic plate 7
atretic plates in 4 ears, and one showed a thin atretic plate (Table I). In 5 ears with mildly hypoplastic external auditory canals, two showed a moderately thick atretic plate, one showed a thin atretic plate, and two ears showed no atretic plate (Table I).
Ossicles The malleus and incus were absent (Fig. 2) in 16 ears (Table III). In 7 ears markedly dysplastic and rudimentary ossicles (Fig. 3) were recognized in the hypoplastic epitympanum (Table III). In 7 ears a single large conglomerate incudomallear mass was attached (Fig. 4) to the atretic plate or epitympanum or both (Table III). If otologic surgery is contemplated, in the presence of atretic plate, the incudomallear mass is most likely to be fused to the plate [8].
Mastoid, mastoid antrum, tegmen tympanum In 8 ears the mastoid was moderately hypoplastic with a few mastoid-air cells (Table IV). The mastoid was markedly hypoplastic or absent in 23 ears (Table IV). The mastoid was considered normal in 3 ears. The mastoid antrum was normal in 5
Fig. 2. Mandibulofacial dysostosis. Frontal tomogram of both temporal bones. Note agenesis of both external auditory canals, with a moderately thick atretic plate on the right and a very thick one on the left. Both tympanic cavities are hypoplastic, and no ossicles are recognized. The upper arrow points to the petrous portion of the fight facial nerve canal and the lower arrow points to its mastoid portion, which is short, superficial, and anterior in location.
233
Fig. 3. Mandibulofacial dysostosis. Frontal tomogram of the temporal bones. Note absence of the right external auditory canal and severely dysplastic left external auditory canal. The tympanic cavity on the right side is almost absent, and on the left side is severely hypoplastic. Note bilateral thick atretic plates, agenesis of the ossicles on the right and rudimentary ossicles on the left (arrow).
Fig. 4. Mandibulofacial dysostosis. Frontal tomogram of the left temporal bone. Note absence of the external auditory canal, thick atretic plate (3) and abnormal conglomerate ossicular mass (1) which is fused to the atretic plate (3). The lateral wall of the attic (2) is normal and the epitympanum is mildly hypoplastic.
234 TABLE IV DEVELOPMENT OF THE MASTOID AIR CELLS, MASTOID ANTRUM AND THE POSITION OF THE TEGMEN IN MFD (34 EARS) Normal Mod.hypoplastic Mar. hypoplastic Normal Hypoplastic Absent mastoid mastoid with few or absent mastoid antrum antrum antrum air cells 3 8 23 5 11 18
Low Normal lying tegmen tegmen 15 19
ears, hypoplastic in 11, a n d a b s e n t in 18 ears (Table IV). Five of the m a r k e d hypoplastic mastoids showed a hypoplastic a n t r u m , a n d in the r e m a i n d e r the a n t r u m was absent. T h e tegmen level was considered low (Fig. 5) in 15 ears a n d n o r m a l in 19 ears. The position of the tegmen is i m p o r t a n t when surgical correction of congenital aural atresia is contemplated. A n extremely low-lying tegmen makes surgical correction very difficult.
Fig. 5. Mandibulofacial dysostosis. Frontal tomogram of the left temporal bone. Note normal vestibule, lateral and superior semicircular canal, and internal auditory canal. The mastoid antrum is absent, and the tegmen tympani is low in position (upper arrows). Note also the thick atretic plate (1), and the entire vertical segment of the facial nerve canal (lower arrows), which is superficial laterally because of hypoplastic and rather flat mastoid.
235
Fig. 6. Mandibulofacial dysostosis. Frontal tomograms of the left temporal bone. The external auditory canal is almost near normal in size, but is closed medially by a thick atretic plate (2). Note moderately bypoplastic tympanic cavity (3), a short lateral wall of the attic (1), and dysplastic ossicles in the hypoplastic attic.
236 Facial nerve canal
The course of the facial nerve canal was normal in 12 ears. In 11 ears the tympanic and vertical segments of the facial nerve canal could not be properly assessed in the tomograms. In 11 ears the vertical portion showed a C-shaped configuration and was more anterior and superficial than normal. In one ear its labyrinthine portion was somewhat Prominent, and its vertical segment was very superficial (Figs. 2, 5).
Inner ear
In mandibulofacial dysostosis, an abnormality of the inner ear is rare and is considered an incidental finding. The cochleas, vestibules, semicircular canals, and internal auditory canals were normal in all 34 ears. The oval window was considered tomographically closed in 4 and normal in 30 ears. The round window was normal in all 34 ears. The cochlear duct was normally visualized in 22 ears and indeterminate in 12 ears. Although no tomographic projections were obtained to visualize the vestibular aqueduct, in 9 ears its course was indentifiable and normal. The carotid canals, jugular fossa, occipital condyles, and hypoglossal canals were normally identifiable in the tomograms. The temporomandibular fossa and the condyle were considered markedly hypoplastic in 26 ears and slightly hypoplastic to nearnormal in 8 ears.
Discussion
In the serial examination of the phenocopy of mandibulofacial dysostosis induced in the rat by the teratogen vitamin A, microscopic study of the induced ear defects revealed that the animal model was closely comparable in all respects to human mandibulofacial dysostosis [11]. The ear cartilages were irregular and reduced in size in experimental animals. The middle ear cavities were small, and there were irregularities in the shape, size, and number of the auditory ossicles. While the middle ear abnormalities were closely comparable on the two sides, there were small differences observed in some instances [11]. Dissection of the middle ear in cases of mandibulofacial dysostosis revealed the same minor discrepancies that are seen in the animal model [11]. The usual embryologic aberration in mandibulofacial dysostosis primarily involves first and second branchial arch derivatives. Therefore, congenital anomalies of the sound-conducting alrparatus in the external and middle ear are the characteristic otologic findings in this syndrome. Abnormalities of the inner ear structures of ectodermal origin theoretically are rare in this syndrome. The external ear is frequently abnormal in shape, size, and position. Extra rudimentary ear tags and blind fistulas may be observed in the same locality. Although patients with this syndrome have been described in whom no deformity of the auricle was present, when microtia is present it is most often symmetric [8].
237 Hutchinson et al. [8] noted symmetric deformities of the external ear in 13 of 16 patients with mandibulofacial dysostosis. Nine of them had grade 1 microtia. Microtia is most often mild (grade 1), but the severity of the hearing loss cannot be predicted exactly on the basis of auricular deformity. In other words, a relative but not absolute relationship is found between the microtia and the external ear canal and middle ear structures. Characteristically in mandibulofacial dysostosis the external auditory canal is most often absent (Fig. 2, 3) or may be hypoplastic (Fig. 3). Occasionally a near-normal external auditory canal may be seen only in those with grade 1 microtia. T h e middle ear cavity in mandibulofacial dysostosis is usually severely deformed. Agenesis of the middle ear cleft is not infrequent (Fig. 3). In the majority of the cases the middle ear cleft is hypoplastic and is closed by an atretic plate (Fig. 2). The bony external auditory canal arises from a solid core of epithelial cells which splits first in its deepest portion to form the outer surface of the tympanic membrane and then canalizes laterally [8]. The atretic plate is the primitive tympanic membrane which may be totally osseous or partially differentiated into a rudimentary tympanic membrane depending upon when developmental arrest occurs (Figs. 2, 3 and 6). Since the embryologic aberration in mandibulofacial dysostosis primarily involves the first and second branchial arch derivatives, deformities of the ossicles are almost always present. Agenesis of the incus and malleus is frequent (Figs. 2 and 3); often they are rudimentary (Figs. 3 and 6). Usually they form a conglomerate bony mass which is fused to the atretic place, the epitympanum, or both (Fig. 4). The stapes, a second branchial arch derivative, is malformed, rudimentary, or absent. Numerous authors have reported abnormalities of the stapes [6,7]. Although the stapes cannot be assessed properly with polydirectional tomogram, stapedial malformations are also common [8]. In the majority of cases, the mastoid and mastoid antrum are either poorly developed or absent (Fig. 5). The tegmen level may be low in position (Fig. 5). The course of the facial nerve canal may be normal; however, the facial nerve may pursue an abnormal course and is located more anteriorly than would be expected (Figs. 2 and 5). Since the membranous labyrinth derives from the ectodermal otocyst and develops independently from the remainder of the ear, which is primarily derived from the branchial apparatus, combined malformations of the inner, middle, and outer ear do not occur frequently [10]. References 1 Axelsson, A., Brolin, 1., Engstrom, H. and Linden, G., Dysostosis mandibulofacialis,J. Laryng., 87 (1963) 575-592. 2 Falzone,S. and Pruzansky,S., Cleft palate and congenital palatopharyngealincompetencyin mandibulofacial dysostosis: frequencyand problems in treatment, Cleft Palate J., 13 (1976) 354-360. 3 Francheschetti,A. and Klein, D., The mandibulofacialdysostosis, a new hereditary syndrome, Acta ophtbal., 27 (1949) 141-224. 4 Gorlin, R.J., Pindborg, J.J.°and Cohem, M.M. Jr., Syndromes of the Head and Neck (2nd edn.), McGraw-Hill, New York, 1976.
238 5 Harrison, S.H., Treacher Collins syndrome, Brit. J. plast. Surg., 3 (1951) 282-290. 6 Herring, S.W., Rowlat, U.F. and Pruzansky, S., Anatomical abnormalities in mandibulofacial dysostosis, Amer. J. reed. Genet., 3 (1979) 225-259. 7 Holbrow, C.A., Deafness and the Treacher Collins syndrome, J. Laryng., 75 (1961) 978-984. 8 Hutchinson, J.C. Jr., Caldarelli, D.D., Valvassori, G.E., Pruzansky, S. and Parris, P.J., The otologlc manifestation or mandibulofacial dysostosis, Otolaryng. Trans., 84 (1977) 520-528. 9 McKenzie, J. and Craig, J., Mandibulofacial dysostosis (Treacher Collins syndrome), Arch. Dis. Childh., 36 (1955) 391-395. 10 Neurmann, Y., Congenital mlcrotia and meatal atresia, Arch. Otolaryng., 66 (1957) 443. 11 Poswillo, D., The pathogenesis of the Treacher Collins syndrome (mandibulofacial dysostosis), Brit. J. oral Surg., 18 (1976) 1-26. 12 Poswillo, D., Etiology and pathogenesis of first and second branchial arch defects: the contribution of animal studies. In: J.M. Converse, J.G. McCarthy and D.M. Smith (Eds.), Symposium on Diagnosis and Treatment of Craniofacial Anomalies, Mosby, St. Louis, 1976, pp. 86-99. 13 Pruzansky, S., The temporomandibular joint. Otolaryng. clin. North Amer., 6 (1973) 523-548. 14 Shprintzen, R.J., Croft, C., Berkman, M.D. and Rakoff, S.J., Pharyngeal hypoplasia in Treacher Collins syndrome, Arch. Otolaryng., 105 (1979) 127-131.