Superior Semicircular Canal Dehiscence: A Missed Finding in Temporal Bone Multidetector CT Scans in Symptomatic Patients Presenting with Vertigo

Objective: To determine the use of multi-detector row computed tomography (CT) in the diagnostic interpretation of superior semicircular canal dehiscence (SSCD) in patients with unapparent aetiology of vertigo thus aiding pre-surgical planning. Materials and Methods: Retrospective temporal bone multidetector CT scans with 0.5 mm image interval including coronal and oblique sagittal and oblique coronal views were obtained and reviewed for the presence of canal dehiscence and dehiscence sizes were recorded in positive cases out of 28 patients who had formerly performed routine CT temporal bone at 1 mm image interval with only coronal and axial views and were reported as normal studies.. Results: The study revealed that 8 patients out of 28 were positive for superior canal dehiscence. Five cases were left sided, 2caseswererightsided,whereas1casewasbilaterallydehiscent.Alldehiscencesweredetectedattheapexofbonycovering of superior semicircular canal, dehiscence size ranged from 2.1 mm to 5.2 mm with a mean of 3.9 mm. In all positive cases, dehiscence was evident at the coronal and oblique planes with 0.5 mm image interval, while only in 1 patient the dehiscence was poorly visualized in coronal images at 1 mm image interval. Conclusion: Good clinical assessment is mandatory for raising the suspicion of SSCD in patients suffering from vertigo, consequent imaging using multidetector row CT scan with 0.5 mm image interval and auxiliary oblique reformatted planes are required for confirming the diagnosis.