Myelopathy Due to Intracranial Dural Arteriovenous Fistula with Perimedullary Venous Drainage: Clinical and Medicolegal Aspects in a Case of Diagnostic Pitfall

Background: Intracranial dural arteriovenous fistula (DAVF) consists of a meshwork of arteriovenous shunts. Drainage of the fistula may be into a dural sinus or directly into cortical veins. Rarely, dural arteriovenous fistulas drain exclusively into perimedullary veins. Prompt diagnosis is important, as the clinical course is potentially life threatening. Case Description: A 67-year-old man presented with difficulties in walking and bladder retention. Magnetic resonance imaging showed central myelopathy, edema from C6 to T8, and dilated posterior medullary veins. Spinal angiography showed no abnormalities. The diagnostic impression was one of inflammatory demyelinating disease, and the patient was treated with corticosteroids. Three days later, the patient had become paraparetic. Brain magnetic resonance imaging showed abnormal vascular structures around the lower brainstem and cervical cord. Cerebral angiography showed a dural fistula at the skull base supplied by the neuromeningeal branch of the ascending pharyngeal artery and draining into the posterior medullary veins. Following neurosurgical referral, the draining vein was clipped just beyond the arterial feeders. At that time, the patient was wheelchair-bound and needed assistance in daily activities. Conclusions: Early diagnosis of this rare vascular malformation is challenging; angiographic studies must include the cranial vasculature when spinal studies are normal or if the abnormality on magnetic resonance imaging is maximal in the upper spinal cord. In the case described, as only medullary angiography was performed, the intracranial dural arteriovenous fistula with perimedullary venous drainage was not diagnosed. Delayed diagnosis is likely to lead to severe neurologic consequences.