[CT analysis of dehiscent sigmoid plate presenting as pulsatile tinnitus]

To evaluate the CT the characteristics of dehiscent sigmoid plate accompanied with pulsatile tinnitus (PT).

Dual phase contrast enhancement CT data of 15 PT patients were analyzed retrospectively.

Dehiscent sigmoid plate was located on the same side of PT in all patients. Thirteen defects had been showed in both CT images and surgery. Among of them, eight defects located on the descending segment, 3 on the superior curve, and the other 2 defects involved the superior curve and descending segment of sigmoid sinus simultaneously. The maximum anteroposterior and vertical diameters of defect measured in CT images were significant larger than that measured during surgery. There were still 5 defects showed in CT images, which did not been found during surgery. Among 9 patients with unilateral dominant brain venous systems, all the dehiscent sigmoid plates were seen on the dominant side. The other 2 patients showed co-dominant brain venous systems, whose the dehiscent sigmoid plates were on the left side. In addition, extensive pneumatized temporal bone filled with air was found in all patients.

Dehiscent sigmoid plate commonly located on the anterior, lateral, or anterolateral wall of the superior curve or descending segment of the sigmoid plate, which usually coexist with the strong unilateral dominant brain venous system and extensive temporal bone pneumatization.