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Bilateral Cochlear Hypoplasia Type IV Presenting With Hearing Loss in a 3-Year-Old Girl
A 3-year-old girl with bilateral sensorineural hearing loss, right greater than left, is found to have bilateral cochlear hypoplasia type IV.
Imaging overview:
Axial non-contrast CT of both temporal bones shows hypoplasia of the middle and apical turns of the cochlea bilaterally. The arrows mark the hypoplastic turns, which sit anteromedially rather than centrally relative to the normal basal turn, which appears preserved on both sides.
Clinical insight:
Cochlear hypoplasia results from arrested cochlear development around the sixth gestational week. Type IV, as in this case, preserves a normal basal turn with hypoplastic middle and apical turns. Other types include a bud-like cochlea (type I), a cystic hypoplastic cochlea with a defective modiolus (type II), and a cochlea with fewer than two turns (type III). Cochlear incomplete partition type II is an important differential, recognized by its “baseball cap” appearance. Review the associated anomalies, including the aberrant labyrinthine facial nerve, semicircular canals, vestibule, vestibular aqueduct, internal auditory canal, and cochlear nerve. Stapedial fixation or a defective footplate can be associated with CSF fistula and meningitis, which matters for surgical planning.
Case courtesy of Kapil Semalti, MD; Shehbaz Ansari, MD; Surjith Vattoth, MD, Rush University Medical Center.