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Congenital malformations of middle and inner ears of parabiotic twins
Congenital Malformations of Middle and Inner Ears of Parabiotic Twins Cemi] Mut]u, MD, ,st Dragoslava R. Djeric, MD, PhD,** Michael M. Paparella, MD, ~ Patricia A. Schachern, BS ~ and Sherry Fulton ~ We descnbe herein the congenital malformations of the mtddle and inner ears in temporal bones of parabtotic, monozygottc twms. Temporal bones were removed from twin B, who had no fetal cardiac activity and was born dead at 23-4/7 weeks, and twin A, the donor or "pump" twm in intrauterine hfe, who died shortly after birth at 20-6/7 weeks. The temporal bones were processed routinely in celotdin, stained wtth hematoxylin and eosm, and examined by light mtcroscopy. We found that twin B had Mondinrs dysplasta with associated deformities of the m~ddle ear and in general showed more developmental anomalies than twin A, and we conclude that Mondmi's dysplasia with anomalies of the m~ddle ear may occur in the parabiottc twm syndrome, and the abnormahttes may be explainable as the result of vascular disturbance, whtch also causes other les~ons m these unusual cases.
(Editorial Comment: The authors speculate possible mechanisms of temporal bone maldevelopment in utero.)
middle and inner ears in temporal bones from
Twin-twin transfusion syndrome, also called intrauterine parabiotic syndrome, is a potentially serious complication of monochorionic
METHODS
gestation of twins. It is a s s o c i a t e d w i t h h i g h p e r i n a t a l m o r b i d i t y a n d m o r t a l i t y as w e l l as i n t r a u t e r i n e fetal death. 1 T w i n - t w i n transfusion s y n d r o m e is the result of u n b a l a n c e d i n t r a u t e r i n e s h u n t i n g of b l o o d f r o m the donort w i n (usually smaller a n d anemic) to the recipient t w i n (usually larger a n d plethoric). Herlitz 2 d e s c r i b e d the first r e p o r t of t w i n - t w i n t r a n s f u s i o n s y n d r o m e in 1941. A l t h o u g h n u m e r o u s studies since t h e n h a v e d e s c r i b e d the clinical findings of this s y n d r o m e , 3 there are no r e p o r t s to date of c o n g e n i t a l m a l f o r m a t i o n s of the ear in p a r a b i o t i c twins. This article d e s c r i b e s c o n g e n i t a l m a l f o r m a t i o n s of the From the *Department of Otolaryngology, Celal Bayar Untversity Medical School, Mantsa, Turkey, tOtitis Medta Research Center, Department of Otolaryngology, University of Minnesota, Minneapohs, MN; *International Hearmg Foundatton, Mmneapohs; and the §Minnesota Ear Head and Neck Clinic, Mmneapohs, MN Supported m part by NIH-NIDCD Grant No P50DC03093001, by the Lions Internattonal of Mmnesota and the International Hearing Foundation, Minneapolis, MN. Address repnnt requests to Patncla A Schachern, BS, Rm 226 Lions Research Labs, 2001 6th St SE, MmneapoIts, MN 55455 Copyrtght© 2000 by W B Saunders Company 0196-0709/00/2101-0008510.00/0 46
p a r a b i o t i c twins.
Temporal bones from these parabiotic twins were obtained at autopsy, fixed by immersion in 10% f o r m a l i n solution, d e c a l c i f i e d in 5% trichloroacetic acid solution, e m b e d d e d in celloidin, a n d s e c t i o n e d at a t h i c k n e s s of 20 p m . E v e r y 10th section w a s stained w i t h h e m a t o x y l i n a n d eosin, a n d the sections w e r e studied b y light m i c r o s c o p y .
Case I Clinical records and autopsy. Twin A, the firstborn, was a male infant whose appearance was consistent with a fetus of 20-6/7 weeks' gestation. The patient had a heart rate of 80 beats per minute immediately after birth but no spontaneous respiration. Intubation was attempted but was unsuccessful because of the small size of his mouth, and he subsequently died. He was delivered occiput anteriorly, with Apgar scores of 1 and 0 at 1 and 5 minutes. He weighed 450 g, had a crown-heel length of 27.2 cm, and a crown-rump length of 19.1 cm. Occipitofrontal circumference was 20.5 cm. His head was noted to be symmetrical with normal facial features. This twin, the donor or " p u m p " twin, had cardiomegaly caused by dilatation of the right side of the heart but did not have an excessively heavy heart. He had hepatosplenomegaly, possibly caused by excessive extramedullary hematopoiesis. Histopathologic observations of the brain disclosed no abnormalities other than premature development.
Amertcan Journal of Otolaryngology,Vo121, No 1 (January-February),2000 pp 46-49
CONGENITAL MALFORMATIONS IN PARABIOTIC TWINS
Histological findings in temporal bone. Findings in the right and left temporal bones were similar. In the right ear, the external auditory canal appeared normal. The tympanic membrane was well developed, with the cartilaginous disc of the manubrium mallei attached to it. The Eustachian tube and middle ear spaces were well developed, and large areas of the middle ear were filled with mesanchyme. The malleus and incus appeared normal for gestational age. The anterior process of the malleus (processus Folianus) was ossified. The stapes was normally developed. The tensor tympani and stapedial muscles were consistent with gestational age. The facial nerve was normal. A large, multifunicular nerve-trunk, most likely the greater superficial petrosal nerve, extended anteriorly to the petrosquamous fissure. The bony canal of the facial nerve was absent throughout most of its course, with the exception of a thin, bony structure covering its tympanic segment. The corda tympaui nerve was in normal position in the middle ear cavity. The internal carotid artery was hypoplastic. All nerves within the internal auditory canal appeared normal. The cochlea had 2.5 turns, but the interosseus septum was undeveloped between turns. Semicircular canals were present and within normal limits, but bone marrow in the mastoid was underdeveloped. The vestibule had a direct communication to the cochlear space (Fig 1). The cochlear and vestibular aqueducts were wide, which was consistent with age. The endolymphatic sac appeared normal. The organ of Corti was atrophic. The spiral ganglion was well developed with a good population of ceils. The vestibular sensory organs were hypoplastic. The stria vascularis was normal, but Reissner's membrane was displaced toward the scala media. The cochlear nerve appeared normal. The round window membrane was well developed, and the round window niche was filled with mesenchyme.
47
Case 2
Clinical records and autopsy. Twin B, the second-born male infant, was delivered prematurely at 23-4/7 weeks. No fetal cardiac activity was noted, and it was believed he had undergone intrauterine fetal demise. He was delivered breech, with Apgar scores of 0 and 0 at 1 and 5 minutes. He weighed 638 g. Crown-heel length was 25.5 cm, and crownrump length was 19 cm. His head was asymmetric and grossly enlarged, with low-set ears. The patient was noted to have agenesis of the nose, nasal cavities, and nasopharynx. He had large bilateral cervical cystic hygromas, atresia of the larynx, and agenesis of the trachea, bronchia, and lungs. The esophagus ended blindly in the thorax without fistula. He had a rudimentary, minute heart with no visible connections. The unusually small brain weighed 34.5 g, but histopathologic observation disclosed no abnormalities other than premature development. His stomach and duodonum were absent with nonrotation of the small and large bowel and a patent anus. The liver, gallbladder, bile ducts, pancreas, and spleen were absent. The urinary tract was unremarkable and patent, as were the adrenal glands. The pituitary gland was unremarkable. Testes were undescended but anatomically unremarkable. This malformed fetus had hydrops fetalis. Each hand was noted to have 3 fingers and I thumb. Both feet had talipers equinovarus with 3 toes on the right foot and 4 on the left. There were contractures of the knees. Histological findings in temporal bone. In the right ear, the external auditory canal and tympanic membrane were underdeveloped and poorly differentiated. The tensor tympani and stapedial muscles looked normal. The eustachian tube was well developed and had no mesenchyme. The middle ear
Fig 1. (A) Normal fetus of 22 weeks' gestation. Note the normal development of interosseus septum between the cochlear turns (arrows) and normal bone marrow in the mastoid (M). (C, cochlea; ME, middle ear; F, facial nerve) (B) Twin A. The cochlea (C) has 2.5 turns with an undeveloped interosseus septum (arrows). The bone marrow in the mastoid (M) is underdeveloped. (V, vestibule; P, posterior semicircular canal. Hematoxylin and eosin; original magnification x l 0 )
48
Fig 2. Twin A. Enlarged vestibule (V) directly communicates with the cochlear space (C). The bony canal of the facial nerve is absent (arrows) and the bone marrow in the mastoid (M) is underdeveloped. S, stapes, (Hematoxylin and eosin; original magnification x l 0 )
space was well developed with large areas filled with mesenchyme. The bony bridge normally seen between the middle ear space and middle cranial fossa was absent. The malleus and incus were malformed, and the stapes had a columellar-type deformity. The stapedial footplate was poorly developed. The area of the oval window niche was filled with cartilage, but both annular ligaments were identified. The facial nerve was normal throughout its intratemporal course, but its bony canal was totally absent. A small nerve-trunk extending toward the petrosquamous fissure probably represented the nervus intermedius (Fig 2). The corda tympani nerve was in normal position in the middle ear cavity. All nerves within the internal auditory canal appeared normal (Fig 3). The internal carotid artery was small, which was consistent with gestational age. The cochlea was short, exhibiting 1.5 turns, and had dysgenesis of the modiolus (Fig 3). The vestibule looked wide, similar to a cloaca, and the lateral and posterior semicircular canals showed dysplasia. The organ of Corti was atrophic. Spiral ganglion
Fig 3. Twin B. The cochlea (C) has 1.5 turns, and the vestibulum (V) is malformed (Mondini's dysplasia). (Hematoxylin and eosin; original magnification x10)
MUTLU ET AL
cells looked normal (Fig 4). Cochlear and vestibular aqueducts were wide, which was consistent with age. The cochlear nerve appeared normal. Vestibular sense organs were hypoplastic. The stria vascularis showed vacuolization. Reissner's membrane was displaced toward the scala media. Utricular and saccular maculae were somewhat flattened, and hair cells were not clearly identifiable. The round-window membrane and roundwindow niche appeared normal. The superior vestibular nerve, passing through the internal auditory canal and middle ear cavity and approaching the lateral semicircular canal crista, was medial to the tympanic segment of the facial nerve. In the left ear, a horizontal asymmetry between left and right temporal bones was detected. The axis of the left temporal bone was spun (anteriorly, inferiorly, and medially so that structures of the middle ear and inner ear were not seen symmetrically) at the same section as those in the right temporal bone. Compared with those on the right, the left cochlea and ossicles were more deeply located. The middle ear cavity was filled with mesenchyme. The malleus and incus were underdeveloped and cartilaginous, with a remnant of Meckel's cartilage. The stapes had a columellar-type deformity, and the stapedial footplate was absent. The corda tympani nerve was not clearly identified in all positions in the middle ear cavity. Other findings were similar to those in the right temporal bone. DISCUSSION
Previous h i s t o p a t h o l o g i c studies of t e m p o ral b o n e s have described congenital anomalies of the m i d d l e a n d i n n e r ears associated w i t h specific entities s u c h as M o n d i n i ' s dysplasia, 4,s Treacher Collins s y n d r o m e , 6 Pierre Robin s y n d r o m e , 7 c h r o m o s o m a l aberrations, 8 con-
Fig 4. Twin B The superior vestibular nerve (arrows) passes through the internal auditory canal and middle ear cavity and approaches the lateral semicircular canal (L). There is atrophy of the posterior semicircular canal (P). C, cochlea. (Hematoxylin and eosin; original magnification x10)
CONGENITAL MALFORMATIONS IN PARABIOTIC TWINS
genital cardiac anomalies, 9 and anencephaly. ~° A few case reports that describe anomalies of the middle and inner ears in conjoined twins have been p u b l i s h e d . 11-13 The literature on parabiotic twin syndrome is characterized by individual case reports. Barth and van der Harten 14 showed a patient with brain lesions that included cystic necrosis and facial hypoplasia with disrupted development in affected areas. Brown and colleagues ~5 reported sonographic findings in 10 cases of the parabiotic twin syndrome. In these cases, discordant fetal size and marked differences in amniotic fluid and lumen were the most common findings. A pregnancy of parabiotic twins may result in intrauterine death of one twin, but the other twin may either survive or suffer from cerebral, renal, and splenic lesions. ~6 In our study, anomalies of the middle and inner ears included underdevelopment, absence, and other abnormalities. Major otologic findings for twin A were absence of the interosseus cochlear septum and abnormal communication of the vestibule and cochlea. In twin B (especially in the left temporal bone) there is underdevelopment of the external auditory canals, tympanic membranes, anterior bony walls of the middle-ear cavity, malleus, incus, and stapes. These findings can be considered to be caused by developmental delay during fetal life. Although the columellar stapes was a major finding in both middle ears for twin B, the stapedial footplate was absent only on the left. Twin B's most unusual anomaly was the superior vestibular nerve that took an abnormal course through the middle-ear cavity. Hypoplasia or aplasia of structures of the inner ear was found in both twins, but especially in twin B. Findings in twin B were a shorter cochlear duct, dysgenesis of the modiolus, dysplasia of the lateral and posterior semicircular canal, severely malformed vestibule (similar to a cloaca), hypoplastic cochlear, and vestibular sensory organs. These anomalies more likely represent Mondini's dysplasia with marked involvement of the vestibular labyrinth and may be caused by the interruption of development in the early embryological stage. It is well known that components of the pars superior (semicircular canals and utricle) are phylogenetically older than components of the pars inferior (saccule and cochlear duct). Findings in this study are at
49
variance with the time-tested rule that embryology mirrors phylogeny, or that the older a structure is phylogenetically, the more resistant it is to developmental defects. 4 The abnormalities in our cases could be explained by vascular disruptions and sequential hypoxic or ischemic events in the ears. This hypothesis has been postulated as a possible mechanism for brain lesions and as the cause of intrauterine death of 1 twin. ~4 Twin B, who had no fetal cardiac activity, was noted to have more developmental anomalies than twin A, who was the donor or " p u m p " twin in intrauterine fetal life. Our study suggests that Mondini's dysplasia with anomalies of the middle ear may occur in the parabiotic twin syndrome. REFERENCES 1. Johnson SF, Dnscoll SG: Twin placentation and its complications. Semin Perinatal 10:9-13, 1986 2. Herlitz G: Zur Kanntnis der anomischen und polyzytamlschen zustaned bm neugeborenen sowei des icterus gravis neonatarum. Acta Pediatr 29:211-253, 1941 3 Myrianthopoulos N: Congenital malformations in twins Acta Genet Med Gemel]ol (Rorna) 25:331-335, 1976 4. Paparella MM: Mondini's dysplasla: A review of histopathology. Ann Otol Rhmol Laryngol 89:1-10, 1980 (supp167) 5. Schuknecht HF: Mondmi's dysplasia: A chmcal and pathologmal study. Ann Otol Rhinol Laryngol 89:1-23, 1980 (suppl 65) 6. Sando I, Hemenway WG, Morgan WR: Histopathology of the temporal bones in mandibulo-facial dysostosls (Treacher-Collins syndrome). Trans Am Acad Ophthalmol Otolaryngol 72:913-924, 1968 7. Igarashl M, Filippine MV, Alford BR: Temporal bone findings in Pierre-Robin syndrome. Laryngoscope 86:16791687, 1976 8. Sando I, Liebermon A, Bergstrom I, et al: Temporal bone hlstopathological findings in trisomy 13 syndrome. Ann Otol Rhinol Laryngo184:1-20, 1975 (suppl 21) 9 Egaml T, Sando I, Myers EN: Temporal bone anomalies associated with congenital heart disease. Ann Otol Rhinol Laryngo188'72-78, 1979 10. Frmdman I, Wright JLW. Temporal bone studies in anencepfialy. J Laryngol Oto194:929-944, 1980 11. Jenkins EW, Watson TR, Mosenthal WT: Surgery in conjoined twins Arch Snrg 76:35-40, 1958 12. Guttmacher AF, Nichols BL' Teratology of conjoined twins. Birth Defects 3:3-9, 1969 13. Igarashi M, Singer DB, Alford BR, et al: Middle and inner ear anomalies in a conjoined twin. Laryngoscope 84:1188-1201, 1974 14. Barth PG, van der Hartan JS: Parablotic twin syndrome with topical isocortical disruption and gastroschisis Acta Neuropathol (Berl) 67:345-349, 1985 15. Brown DL, Bensen CB, Driscoll SG, et ah Twin-twin transfusion syndrome: sonographic findings. Radiology 170'61-63, 1989 16. Gosseye S, Golaire MC, Zarroche JCL. Cerebral, renal and splenic lesions due to fetal anoxia and their relationship to malformations. Dev Med Child Neurol 24:510-518, 1982
(Editorial Comment: The authors speculate possible mechanisms of temporal bone maldevelopment in utero.)
middle and inner ears in temporal bones from
Twin-twin transfusion syndrome, also called intrauterine parabiotic syndrome, is a potentially serious complication of monochorionic
METHODS
gestation of twins. It is a s s o c i a t e d w i t h h i g h p e r i n a t a l m o r b i d i t y a n d m o r t a l i t y as w e l l as i n t r a u t e r i n e fetal death. 1 T w i n - t w i n transfusion s y n d r o m e is the result of u n b a l a n c e d i n t r a u t e r i n e s h u n t i n g of b l o o d f r o m the donort w i n (usually smaller a n d anemic) to the recipient t w i n (usually larger a n d plethoric). Herlitz 2 d e s c r i b e d the first r e p o r t of t w i n - t w i n t r a n s f u s i o n s y n d r o m e in 1941. A l t h o u g h n u m e r o u s studies since t h e n h a v e d e s c r i b e d the clinical findings of this s y n d r o m e , 3 there are no r e p o r t s to date of c o n g e n i t a l m a l f o r m a t i o n s of the ear in p a r a b i o t i c twins. This article d e s c r i b e s c o n g e n i t a l m a l f o r m a t i o n s of the From the *Department of Otolaryngology, Celal Bayar Untversity Medical School, Mantsa, Turkey, tOtitis Medta Research Center, Department of Otolaryngology, University of Minnesota, Minneapohs, MN; *International Hearmg Foundatton, Mmneapohs; and the §Minnesota Ear Head and Neck Clinic, Mmneapohs, MN Supported m part by NIH-NIDCD Grant No P50DC03093001, by the Lions Internattonal of Mmnesota and the International Hearing Foundation, Minneapolis, MN. Address repnnt requests to Patncla A Schachern, BS, Rm 226 Lions Research Labs, 2001 6th St SE, MmneapoIts, MN 55455 Copyrtght© 2000 by W B Saunders Company 0196-0709/00/2101-0008510.00/0 46
p a r a b i o t i c twins.
Temporal bones from these parabiotic twins were obtained at autopsy, fixed by immersion in 10% f o r m a l i n solution, d e c a l c i f i e d in 5% trichloroacetic acid solution, e m b e d d e d in celloidin, a n d s e c t i o n e d at a t h i c k n e s s of 20 p m . E v e r y 10th section w a s stained w i t h h e m a t o x y l i n a n d eosin, a n d the sections w e r e studied b y light m i c r o s c o p y .
Case I Clinical records and autopsy. Twin A, the firstborn, was a male infant whose appearance was consistent with a fetus of 20-6/7 weeks' gestation. The patient had a heart rate of 80 beats per minute immediately after birth but no spontaneous respiration. Intubation was attempted but was unsuccessful because of the small size of his mouth, and he subsequently died. He was delivered occiput anteriorly, with Apgar scores of 1 and 0 at 1 and 5 minutes. He weighed 450 g, had a crown-heel length of 27.2 cm, and a crown-rump length of 19.1 cm. Occipitofrontal circumference was 20.5 cm. His head was noted to be symmetrical with normal facial features. This twin, the donor or " p u m p " twin, had cardiomegaly caused by dilatation of the right side of the heart but did not have an excessively heavy heart. He had hepatosplenomegaly, possibly caused by excessive extramedullary hematopoiesis. Histopathologic observations of the brain disclosed no abnormalities other than premature development.
Amertcan Journal of Otolaryngology,Vo121, No 1 (January-February),2000 pp 46-49
CONGENITAL MALFORMATIONS IN PARABIOTIC TWINS
Histological findings in temporal bone. Findings in the right and left temporal bones were similar. In the right ear, the external auditory canal appeared normal. The tympanic membrane was well developed, with the cartilaginous disc of the manubrium mallei attached to it. The Eustachian tube and middle ear spaces were well developed, and large areas of the middle ear were filled with mesanchyme. The malleus and incus appeared normal for gestational age. The anterior process of the malleus (processus Folianus) was ossified. The stapes was normally developed. The tensor tympani and stapedial muscles were consistent with gestational age. The facial nerve was normal. A large, multifunicular nerve-trunk, most likely the greater superficial petrosal nerve, extended anteriorly to the petrosquamous fissure. The bony canal of the facial nerve was absent throughout most of its course, with the exception of a thin, bony structure covering its tympanic segment. The corda tympaui nerve was in normal position in the middle ear cavity. The internal carotid artery was hypoplastic. All nerves within the internal auditory canal appeared normal. The cochlea had 2.5 turns, but the interosseus septum was undeveloped between turns. Semicircular canals were present and within normal limits, but bone marrow in the mastoid was underdeveloped. The vestibule had a direct communication to the cochlear space (Fig 1). The cochlear and vestibular aqueducts were wide, which was consistent with age. The endolymphatic sac appeared normal. The organ of Corti was atrophic. The spiral ganglion was well developed with a good population of ceils. The vestibular sensory organs were hypoplastic. The stria vascularis was normal, but Reissner's membrane was displaced toward the scala media. The cochlear nerve appeared normal. The round window membrane was well developed, and the round window niche was filled with mesenchyme.
47
Case 2
Clinical records and autopsy. Twin B, the second-born male infant, was delivered prematurely at 23-4/7 weeks. No fetal cardiac activity was noted, and it was believed he had undergone intrauterine fetal demise. He was delivered breech, with Apgar scores of 0 and 0 at 1 and 5 minutes. He weighed 638 g. Crown-heel length was 25.5 cm, and crownrump length was 19 cm. His head was asymmetric and grossly enlarged, with low-set ears. The patient was noted to have agenesis of the nose, nasal cavities, and nasopharynx. He had large bilateral cervical cystic hygromas, atresia of the larynx, and agenesis of the trachea, bronchia, and lungs. The esophagus ended blindly in the thorax without fistula. He had a rudimentary, minute heart with no visible connections. The unusually small brain weighed 34.5 g, but histopathologic observation disclosed no abnormalities other than premature development. His stomach and duodonum were absent with nonrotation of the small and large bowel and a patent anus. The liver, gallbladder, bile ducts, pancreas, and spleen were absent. The urinary tract was unremarkable and patent, as were the adrenal glands. The pituitary gland was unremarkable. Testes were undescended but anatomically unremarkable. This malformed fetus had hydrops fetalis. Each hand was noted to have 3 fingers and I thumb. Both feet had talipers equinovarus with 3 toes on the right foot and 4 on the left. There were contractures of the knees. Histological findings in temporal bone. In the right ear, the external auditory canal and tympanic membrane were underdeveloped and poorly differentiated. The tensor tympani and stapedial muscles looked normal. The eustachian tube was well developed and had no mesenchyme. The middle ear
Fig 1. (A) Normal fetus of 22 weeks' gestation. Note the normal development of interosseus septum between the cochlear turns (arrows) and normal bone marrow in the mastoid (M). (C, cochlea; ME, middle ear; F, facial nerve) (B) Twin A. The cochlea (C) has 2.5 turns with an undeveloped interosseus septum (arrows). The bone marrow in the mastoid (M) is underdeveloped. (V, vestibule; P, posterior semicircular canal. Hematoxylin and eosin; original magnification x l 0 )
48
Fig 2. Twin A. Enlarged vestibule (V) directly communicates with the cochlear space (C). The bony canal of the facial nerve is absent (arrows) and the bone marrow in the mastoid (M) is underdeveloped. S, stapes, (Hematoxylin and eosin; original magnification x l 0 )
space was well developed with large areas filled with mesenchyme. The bony bridge normally seen between the middle ear space and middle cranial fossa was absent. The malleus and incus were malformed, and the stapes had a columellar-type deformity. The stapedial footplate was poorly developed. The area of the oval window niche was filled with cartilage, but both annular ligaments were identified. The facial nerve was normal throughout its intratemporal course, but its bony canal was totally absent. A small nerve-trunk extending toward the petrosquamous fissure probably represented the nervus intermedius (Fig 2). The corda tympani nerve was in normal position in the middle ear cavity. All nerves within the internal auditory canal appeared normal (Fig 3). The internal carotid artery was small, which was consistent with gestational age. The cochlea was short, exhibiting 1.5 turns, and had dysgenesis of the modiolus (Fig 3). The vestibule looked wide, similar to a cloaca, and the lateral and posterior semicircular canals showed dysplasia. The organ of Corti was atrophic. Spiral ganglion
Fig 3. Twin B. The cochlea (C) has 1.5 turns, and the vestibulum (V) is malformed (Mondini's dysplasia). (Hematoxylin and eosin; original magnification x10)
MUTLU ET AL
cells looked normal (Fig 4). Cochlear and vestibular aqueducts were wide, which was consistent with age. The cochlear nerve appeared normal. Vestibular sense organs were hypoplastic. The stria vascularis showed vacuolization. Reissner's membrane was displaced toward the scala media. Utricular and saccular maculae were somewhat flattened, and hair cells were not clearly identifiable. The round-window membrane and roundwindow niche appeared normal. The superior vestibular nerve, passing through the internal auditory canal and middle ear cavity and approaching the lateral semicircular canal crista, was medial to the tympanic segment of the facial nerve. In the left ear, a horizontal asymmetry between left and right temporal bones was detected. The axis of the left temporal bone was spun (anteriorly, inferiorly, and medially so that structures of the middle ear and inner ear were not seen symmetrically) at the same section as those in the right temporal bone. Compared with those on the right, the left cochlea and ossicles were more deeply located. The middle ear cavity was filled with mesenchyme. The malleus and incus were underdeveloped and cartilaginous, with a remnant of Meckel's cartilage. The stapes had a columellar-type deformity, and the stapedial footplate was absent. The corda tympani nerve was not clearly identified in all positions in the middle ear cavity. Other findings were similar to those in the right temporal bone. DISCUSSION
Previous h i s t o p a t h o l o g i c studies of t e m p o ral b o n e s have described congenital anomalies of the m i d d l e a n d i n n e r ears associated w i t h specific entities s u c h as M o n d i n i ' s dysplasia, 4,s Treacher Collins s y n d r o m e , 6 Pierre Robin s y n d r o m e , 7 c h r o m o s o m a l aberrations, 8 con-
Fig 4. Twin B The superior vestibular nerve (arrows) passes through the internal auditory canal and middle ear cavity and approaches the lateral semicircular canal (L). There is atrophy of the posterior semicircular canal (P). C, cochlea. (Hematoxylin and eosin; original magnification x10)
CONGENITAL MALFORMATIONS IN PARABIOTIC TWINS
genital cardiac anomalies, 9 and anencephaly. ~° A few case reports that describe anomalies of the middle and inner ears in conjoined twins have been p u b l i s h e d . 11-13 The literature on parabiotic twin syndrome is characterized by individual case reports. Barth and van der Harten 14 showed a patient with brain lesions that included cystic necrosis and facial hypoplasia with disrupted development in affected areas. Brown and colleagues ~5 reported sonographic findings in 10 cases of the parabiotic twin syndrome. In these cases, discordant fetal size and marked differences in amniotic fluid and lumen were the most common findings. A pregnancy of parabiotic twins may result in intrauterine death of one twin, but the other twin may either survive or suffer from cerebral, renal, and splenic lesions. ~6 In our study, anomalies of the middle and inner ears included underdevelopment, absence, and other abnormalities. Major otologic findings for twin A were absence of the interosseus cochlear septum and abnormal communication of the vestibule and cochlea. In twin B (especially in the left temporal bone) there is underdevelopment of the external auditory canals, tympanic membranes, anterior bony walls of the middle-ear cavity, malleus, incus, and stapes. These findings can be considered to be caused by developmental delay during fetal life. Although the columellar stapes was a major finding in both middle ears for twin B, the stapedial footplate was absent only on the left. Twin B's most unusual anomaly was the superior vestibular nerve that took an abnormal course through the middle-ear cavity. Hypoplasia or aplasia of structures of the inner ear was found in both twins, but especially in twin B. Findings in twin B were a shorter cochlear duct, dysgenesis of the modiolus, dysplasia of the lateral and posterior semicircular canal, severely malformed vestibule (similar to a cloaca), hypoplastic cochlear, and vestibular sensory organs. These anomalies more likely represent Mondini's dysplasia with marked involvement of the vestibular labyrinth and may be caused by the interruption of development in the early embryological stage. It is well known that components of the pars superior (semicircular canals and utricle) are phylogenetically older than components of the pars inferior (saccule and cochlear duct). Findings in this study are at
49
variance with the time-tested rule that embryology mirrors phylogeny, or that the older a structure is phylogenetically, the more resistant it is to developmental defects. 4 The abnormalities in our cases could be explained by vascular disruptions and sequential hypoxic or ischemic events in the ears. This hypothesis has been postulated as a possible mechanism for brain lesions and as the cause of intrauterine death of 1 twin. ~4 Twin B, who had no fetal cardiac activity, was noted to have more developmental anomalies than twin A, who was the donor or " p u m p " twin in intrauterine fetal life. Our study suggests that Mondini's dysplasia with anomalies of the middle ear may occur in the parabiotic twin syndrome. REFERENCES 1. Johnson SF, Dnscoll SG: Twin placentation and its complications. Semin Perinatal 10:9-13, 1986 2. Herlitz G: Zur Kanntnis der anomischen und polyzytamlschen zustaned bm neugeborenen sowei des icterus gravis neonatarum. Acta Pediatr 29:211-253, 1941 3 Myrianthopoulos N: Congenital malformations in twins Acta Genet Med Gemel]ol (Rorna) 25:331-335, 1976 4. Paparella MM: Mondini's dysplasla: A review of histopathology. Ann Otol Rhmol Laryngol 89:1-10, 1980 (supp167) 5. Schuknecht HF: Mondmi's dysplasia: A chmcal and pathologmal study. Ann Otol Rhinol Laryngol 89:1-23, 1980 (suppl 65) 6. Sando I, Hemenway WG, Morgan WR: Histopathology of the temporal bones in mandibulo-facial dysostosls (Treacher-Collins syndrome). Trans Am Acad Ophthalmol Otolaryngol 72:913-924, 1968 7. Igarashl M, Filippine MV, Alford BR: Temporal bone findings in Pierre-Robin syndrome. Laryngoscope 86:16791687, 1976 8. Sando I, Liebermon A, Bergstrom I, et al: Temporal bone hlstopathological findings in trisomy 13 syndrome. Ann Otol Rhinol Laryngo184:1-20, 1975 (suppl 21) 9 Egaml T, Sando I, Myers EN: Temporal bone anomalies associated with congenital heart disease. Ann Otol Rhinol Laryngo188'72-78, 1979 10. Frmdman I, Wright JLW. Temporal bone studies in anencepfialy. J Laryngol Oto194:929-944, 1980 11. Jenkins EW, Watson TR, Mosenthal WT: Surgery in conjoined twins Arch Snrg 76:35-40, 1958 12. Guttmacher AF, Nichols BL' Teratology of conjoined twins. Birth Defects 3:3-9, 1969 13. Igarashi M, Singer DB, Alford BR, et al: Middle and inner ear anomalies in a conjoined twin. Laryngoscope 84:1188-1201, 1974 14. Barth PG, van der Hartan JS: Parablotic twin syndrome with topical isocortical disruption and gastroschisis Acta Neuropathol (Berl) 67:345-349, 1985 15. Brown DL, Bensen CB, Driscoll SG, et ah Twin-twin transfusion syndrome: sonographic findings. Radiology 170'61-63, 1989 16. Gosseye S, Golaire MC, Zarroche JCL. Cerebral, renal and splenic lesions due to fetal anoxia and their relationship to malformations. Dev Med Child Neurol 24:510-518, 1982