Otocephaly is a lethal malformation of the first and second branchial arches, which consists of ventromedial displacement of the external ear structures (synotia), mandibular aplasia (agnathia), absence of the tongue [aglossia], and microstomia. We present the first complete description of the temporal bone findings in a case of otocephalus. A three-dimensional computer-assisted reconstruction of the right temporal bone was performed, allowing a unique graphic analysis. An extremely low-lying middle fossa tegmen was noted with malrotation of the middle ear structures. Severe ossicular malformations were also found. An anomalous course of the internal carotid artery was noted with indentation of the basal turn of the cochlea. All three layers of the otic capsule were incompletely developed. Cochlear bony dehiscences were noted. These findings are consistent with early arrest of fetal development and malrotation caused by lack of growth pressure from the mandibular arch. Implications of these findings in the embryologic development of the ear are discussed.
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