NORMAL MODIOLUS - CT APPEARANCE IN PATIENTS WITH A LARGE VESTIBULAR AQUEDUCT

PURPOSE: To determine the computed tomographic (CT) appearance of the normal modiolus and the pathologic alteration in patients with a large vestibular aqueduct and an otherwise normal-appearing cochlea. MATERI ALS AND METHODS: Temporal bone CT studies obtained before and after a major upgrade of CT capability in 1992 were reviewed in four groups: G roup A (1.5-mm section thickness) comprised 50 normal ears in 43 patie nts, group B (1-mm section thickness) comprised 75 normal ears in 50 p atients, group C (1.5-mm section thickness) comprised 16 ears with a l arge vestibular aqueduct in 10 patients, and group D (1-mm section thi ckness) comprised 23 ears with a large vestibular aqueduct in 12 patie nts. All groups comprised adult and pediatric patients. RESULTS: In gr oups A and B, the normal modiolus was visualized in 90% and 100% of ea rs, respectively. In groups C and D, with a total of 39 ears with a la rge vestibular aqueduct and an otherwise normal cochlea, modiolar defi ciency was demonstrated in 100% of ears. CONCLUSION: CT is an excellen t technique for depicting the cochlear modiolus. Results suggest that all ears with a large vestibular aqueduct have associated cochlear mod iolar deficiencies. Thus, a large vestibular aqueduct may be only occa sionally, if ever, an isolated developmental anomaly of the inner ear.