Christopher Trimble MD, MBA, Presenter: Nothing to Disclose

David Eisenman MD, Abstract Co-Author: Nothing to Disclose

Dheeraj Gandhi MBBS, MD, Abstract Co-Author: Nothing to Disclose

Robert Emmanuel Morales MD, Abstract Co-Author: Nothing to Disclose

Dehiscence of the sigmoid plate overlying the sigmoid sinus has been reported as a surgically treatable cause of pulsatile tinnitus. We investigated the incidence of this as an incidental finding in patients without a documented history of pulsatile tinnitus.

Using a retrospective review, we evaluated thin section (1 mm slice thickness) temporal bone CT scans of 125 consecutive trauma patients (102 male and 23 female, with an average age of 39 years) imaged according to a standard institutional trauma protocol during a 9 month period. Sigmoid plate dehiscence was defined as an imperceptible well defined osseous barrier between the sigmoid sinus and adjacent pneumatized mastoid air cells on at least three consecutive images reconstructed in the axial plane, parallel to the hard palate. This finding was confirmed on a second plane. Patients with temporal bone fractures were excluded.

Twenty-five patients in the series were excluded due to temporal bone fractures. Of the 100 remaining patients, 5 (3 male and 2 female) met criteria for sigmoid plate dehiscence. The areas of sigmoid plate dehiscence exclusively involved the junction of the transverse and sigmoid sinuses on the right side. The average dehiscent diameter was 5.8mm (min 3.8mm, max 7.6mm).

Though the prevalence of pulsatile tinnitus attributable to sigmoid plate dehiscence has been estimated at 20%, the prevalence of this finding in the asymptomatic population has not been previously reported. Using our diagnostic criteria, surveying 100 trauma patients, we found the prevalence to be 5%. Patients in our series demonstrated dehiscence exclusively on the right side and located at the junction of the transverse and sigmoid sinuses. 

The prevalence of sigmoid plate dehiscence in the asymptomatic population appears quite low; its CT diagnosis in evaluating pulsatile tinnitus is key because surgical treatment has high success rates.

Trimble, C, Eisenman, D, Gandhi, D, Morales, R, Sigmoid Plate Dehiscence: The Prevalence as an Incidental Finding in Patients without Pulsatile Tinnitus.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13021199.html