High-resolution CT findings suggest a developmental abnormality underlying superior canal dehiscence syndrome.

Objective: Patients with superior canal dehiscence (SCD) syndrome experience vertigo and oscillopsia with loud sounds and/or stimuli that result in changes in middle ear or intracranial pressure. Findings on temporal bone CT were analyzed to determine if a developmental abnormality is associated with the syndrome.

Material And Methods: Temporal bone CT scans [0.5 mm collimation and projections into the superior semicircular canal (SC) plane] were used to compare the bone overlying the SC in patients with SCD syndrome (20 unilateral, 7 bilateral) and in 88 patients without SCD syndrome who had undergone temporal bone CT for evaluation of other otologic disorders (controls).

Results: The thickness of bone overlying the SC in the controls measured 0.67 +/- 0.38 mm (mean +/- SD). For individual control subjects. the thickness of bone on one side was correlated with that on the other side (r = 0.43; p < 0.0001). The thickness of bone overlying the SC on the intact side in patients with unilateral dehiscence measured 0.31 +/- 0.23 mm, and was thinner than that noted in the controls (p < 0.0001).

Conclusion: These findings support the notion that there is a developmental abnormality underlying SCD syndrome. When dehiscence is found on one side, the contralateral side is likely to be thin.