Diverticula of the Superior Petrosal Sinus Leading to Superior Semicircular Canal Dehiscence

Background Since its initial description nearly two decades ago, superior semicircular canal dehiscence (SSCD) has quickly moved to the forefront of research and clinical practice in neurotology. Anatomically, the superior semicircular canal resides in close proximity to the superior petrosal sinus (SPS), and previous literature has described cases in which dehiscence of the SSCD involves the SPS. This study investigates a subset of these cases that distinctly involve a venous anomaly, most notably a diverticulum, of the SPS.

Methods A multicenter retrospective review was performed to identify cases of SSCD involving the SPS. From the relevant cases, available radiologic studies were then reviewed by a board certified neurotologist and neuroradiologist to determine the relationship of these two structures. Cases that unequivocally involved a SPS diverticulum were selected for analysis.

Results Five cases were identified. The average of these patients was 65.9 years (median: 64.9, range: 59–74). Lesions were more commonly left sided and more commonly involved the dominant side of intracranial venous drainage. Anatomic connections between the subarcuate artery and the SPS were radiographically seen in proximity to the area of superior canal dehiscence in most cases, though no patient had formal angiography to further evaluate the presence of an arteriovenous fistula (AVF). The most common symptoms were vertigo (80%), exercise/Valsalva-induced vertigo (60%), pulsatile tinnitus (60%), and aural fullness (60%). Only one patient underwent surgical intervention, which involved a transmastoid approach to superior canal dehiscence plugging. Approximately 6 months following surgery, the patient had no clear improvement in their symptoms. Otherwise, patients were observed, only one of whom had substantial clinical follow-up. At 60 months following diagnosis, the latter patient reported no significant change in symptoms, aside from a single episode of benign paroxysmal positional vertigo, which resolved after an Epley’s maneuver.

Conclusion SPS-associated SSCD appears to be a relatively rare, despite the close anatomic relationship between these two structures. We have previously reported on a classification system regarding this form of dehiscence. However, in a distinct subset of cases that involve a venous diverticulum arising from the SPS, patients may be more likely to present with exercise/Valsalva-induced vertigo or pulsatile tinnitus. Additionally, reviewing existing radiographic studies would suggest the potential for AVF formation as an etiologic consideration in these cases, and further evaluation with dedicated angiography should be considered in this setting moving forward.