Radiographic examination of patients with dehiscence of semicircular canals with digital volume tomography.

Digital volume tomography (DVT) is an extension of panoramic tomography. With this diagnostic technique, characterized by high resolution, a narrow section width (0.125 mm), and three-dimensional display, small pathological processes can be well visualized. We examined 434 patients with DVT (Accu-I-tomo, Morita, Japan). Eleven patients with a history of peripheral vertigo presented a fistula of the labyrinth. The results were compared with intraoperative findings to evaluate the diagnostic value of DVT in cases of erosion of the semicircular canals. With high resolution and artifact-free demonstration of the labyrinth and inner ear structures, it was possible to determine the presence of a fistula of the semicircular canals in all 11 patients. An erosion of the lateral semicircular canal was found in nine patients with additional fistulae of the superior and posterior semicircular canals in one patient, a dehiscence of bone of the superior semicircular canal in one patient, and a dehiscence of the posterior semicircular canal in another patient. The predicted erosion of semicircular canals was verified in all patients during surgery where a closure of the fistulae was performed. DVT is an excellent technique to examine the semicircular canal structures in patients with peripheral vertigo, and expand the application of diagnostic possibilities in the lateral skull base. With this method, the preoperative diagnosis is improved allowing more accurate planning of the surgical procedure. DVT delivers a small radiation dose with a high resolution and a low purchase price for the equipment.