Transmastoid access in branchio-oto-renal syndrome: A reappraisal of computed tomography imaging.

Objective: To evaluate for temporal bone abnormalities that might affect transmastoid surgery such as cochlear implantation in cases of branchio-oto-renal syndrome (BOR).

Study Design: Retrospective review.

Methods: Qualitative assessment of temporal bone computed tomography imaging was performed by a neuroradiologist for 30 individuals with BOR (60 ears) and 20 controls with normal hearing (20 ears). Transmastoid access was assessed categorically across 4 features: tip development, cortex pneumatization, tegmen height, and facial recess pneumatization. The appearance of 4 standard landmarks (Koerner's septum, antrum, prominence of the horizontal semicircular canal, incudal short process) was also dichotomized as normal or abnormal. Data were compared using Fisher's exact testing.

Results: Mastoid height differed between the groups with tip underdevelopment noted in 72% of BOR ears vs. 40% of controls (p = 0.02), and a low tegmen was seen in 68% of BOR ears and 25% of controls (p < 0.01). Significant differences in pneumatization were also found for the mastoid cortex (28% non-pneumatized in BOR vs. 5% in controls; p = 0.03) and the facial recess (27% non-pneumatized in BOR vs. 0% in controls; p = 0.01). Standard landmarks were easily identified in all of the control mastoids. In the BOR group, Koerner's septum was abnormally located or absent in 45%, and the antrum was severely hypoplastic or absent in 50%. Similarly, the prominence of the horizontal semicircular canal and the short process of the incus were dysplastic in 73% (44/60) and 62% (37/60), respectively.

Conclusions: Mastoid abnormalities are common in BOR syndrome. Restricted transmastoid access and abnormal or absent mastoid landmarks should be anticipated in those patients with BOR who become cochlear implant candidates.

Level Of Evidence: 4.