Three Familial Cases of Michel’s Aplasia *Ahmad Daneshi, *Mohammad Farhadi, *Alimohamad Asghari, †Hesamedin Emamjomeh, †Parvaneh Abbasalipour, and ‡Saeed Hasanzadeh *Department of Otolaryngology–Head and Neck Surgery, and †Department of Audiology, Hazrat Rasoul Akram Hospital, Iran University of the Medical Sciences, Tehran, Iran; and ‡Iranian Cochlear Implant Center, Tehran, Iran Complete agenesis of the bony labyrinth, first described by Michel, represents the most severe form of inner ear defect. A search of the literature yielded only one report of this rare anomaly, affecting two siblings. Three familial cases of bilat- eral inner ear aplasia are reported here, and the probable inher- itance pattern of this condition is discussed. Key Words: Apla- sia–Hearing Loss–Sensorineural. Otol Neurotol 23:346–348, 2002. In 1863, Michel (1) reported a case of bilateral com- plete bony and membranous aplasia of the inner ear. Embryologically, the otic placode begins to differentiate into the structures of the inner ear during the third week of gestation. Complete inner ear aplasia results when development ceases before this time (2,3). Recently, the role of otic capsule formation in mesenchymal differen- tiation was reported, as well as the effect of the deletion of the homeobox gene on the development of the ear, the cranial nerves, and the hindbrain (4). We describe three familial cases of bilateral inner ear aplasia. CASE REPORTS A 3-year-old boy, his 11-year-old brother, and their 7-year-old cousin were referred to our clinic for auditory rehabilitation by cochlear implantation. Patient 1 The patient was a 3-year-old boy with profound bilat- eral congenital sensorineural hearing loss whose parents were cousins. His mother’s father and uncle were congenitally deaf, but other data about them were not available, because they had died. The patient had been delivered vaginally and had a normal Apgar score and birthweight (3,500 g). His mother did not report taking any medication during pregnancy. The results of his physical examination were normal, except for a func- tional 1 / 6 heart murmur that was heard on the left sternal border. The patient’s tympanogram was normal. The patient did not respond to auditory stimulation of either ear dur- ing pure-tone audiometric tests. Auditory brainstem re- sponse (ABR) testing with click stimulation (130-dB sound pressure level) during the neonatal period and at age 2 years demonstrated no response on either side. Computed tomographic (CT) scans in the axial and co- ronal views showed bilateral absence of the inner ear structures and petrous bone (Fig. 1). The middle ear cav- ity, the course of the facial nerve, and the internal audi- tory canal were normal. T1-weighted and T2-weighted magnetic resonance imaging (MRI) showed bilateral ab- sence of the inner ear structures and the VIIIth cranial nerves. The patient had used a tactile hearing aid for more than 2 months with no benefit when he was 2 years of age. Patient 2 The patient was the 11-year-old brother of Patient 1 and had the same condition and family history. He had previously undergone two cardiovascular surgical proce- dures for congenital cardiac anomalies (pulmonary ste- nosis, atrial septal defect, and Type 1B tricuspid atresia, which were disclosed by performing angiography). The results of his physical examination were normal, except for a continuous heart murmur on the left sternal border. Pure-tone audiometry and ABR testing demonstrated no response on either side. CT (Fig. 2) and MRI scans dem- onstrated bilateral absence of the inner ear structures and the VIIIth cranial nerve. Patient 3 The patient was a 7-year-old girl, a cousin of Patients 1 and 2, with the same condition. Her parents were cousins. ABR testing with click stimulation 130-dB SPL demonstrated no response on either side. The results Address correspondence and reprint requests to Alimohamad Asghari, M.D., Department of Otorhinolaryngology, Hazrat Rasoul Akram Hospital, St. Niayesh, Ave. Satarkhan, Tehran, Iran. Email: entdepar@hbi.dmr.or.ir Otology & Neurotology 23:346–348 © 2002, Otology & Neurotology, Inc. 346