Subdural hematoma from an acquired dural arteriovenous fistula following external ventricular drain placement for subarachnoid hemorrhage

Objective: Intracranial dural arteriovenous fistulas represent pathological connections between dural arteries and dural veins, dural sinuses or meningeal veins in the absence of an intervening capillary bed. They are thought to be acquired secondary to trauma, surgery, sinus thrombosis, venous hypertension or arterial dysplasia. Methods: A 66-year-old Asian female presented with subarachnoid hemorrhage secondary to ruptured 2-mm saccular aneurysm of the left middle cerebral artery associated with fusiform dilatation. It was successfully treated with endovascular coiling. A right frontal external ventricular drain was also placed to treat her hydrocephalus. On post-bleed day 10, she became acutely unresponsive with a fixed and dilated right pupil. Head CT was obtained and revealed an acute right subdural hematoma which was emergently evacuated. Results: No obvious bleeders were identified during surgery. Patient improved and repeat catheter angiography a week later showed a new dural arteriovenous fistula fed by the anterior falcine artery and the middle meningeal artery to a cortical vein draining into the superior sagittal sinus. Conclusion: We hope that the present report will raise awareness to treating physicians to be cognizant of this unusual complication in their differential diagnosis when treating patients with an EVD in place.