Extra-luminal sigmoid sinus granulation tissue resulting in otitic hydrocephalus

Summary A four-year-old male presented to the emergency department with bilateral cranial nerve VI palsy following a failed outpatient course of antibiotics for acute mastoiditis. Imaging revealed a right sigmoid sinus flow defect. Urgent mastoidectomy with removal of the right sigmoid sinus osseous plate was performed. Intraoperatively, extensive granulation tissue was encountered compressing the sinus. The cranial nerve deficit resolved overnight, and follow-up imaging revealed restoration of venous outflow. As a result, the flow void was determined to be a result of compression of the sinus rather than thrombosis, and a prolonged course of systemic anticoagulation was avoided.