INTRODUCTION: Dural arteriovenous fistulae (DAVF) are relatively rare lesions that are composed of abnormal connections between dural arteries and usually adjacent cortical veins. Their true incidence is unknown. 1 Diagnosis is oftentimes difficult because the clinical and radiological findings are similar with the much more frequent spinal DAVFs.8 We report a case of DAVF with an even more rarely seen venous drainage into the perimedullary veins.

CASE: A 37-year-old, female, Filipino presented with progressive motor weakness of all extremities for 3 years. Initial neuroimaging studies of the brain and spinal cord were interpreted as normal despite progressive clinical deterioration. A cranial angiogram was then done which showed a DAVF at the right cerebellar dura mainly supplied by the branches of the right ECA. Several stages of coil and nBCA glue embolization were done on the supplying arterial branches but the patient failed to improve clinically. The patient was referred to our institution's Neuroendovascular Team and review of all previous studies done showed multiple proximal branches of the right BCA forming a low flow extracranial dural fistula with bilateral perimedullary veins. This was exacerbated by continuous recruitment of arterial feeders due to failure of previous embolization procedures.

DISCUSSIONS: Intracranial DAVFs with spinal perimedullary venous drainage are rare lesions and only a relatively small number of cases have been reported.8,10-15The pathophysiologic mechanism of the progressive spinal cord deficits is due to spinal cord venous hypertension and secondary cord swelling.8 Fistulas localized in the intracranial dura mater can give rise to congestion of the spinal venous system via the anastomotic channels between the veins of the posterior cranial fossa and the spinal perimedullary veins.15 Our patient had extensive spinal venous drainage descending to the thoracic spinal cord from the onset and thereby underwent progressive myelopathy. Because the fistula was low flow in character, motor symptoms were very gradual. Our patient presented with symptoms suggestive of spinal rather than intracranial origin. The diagnostic and subsequent therapeutic delays resulted in a never-ending and perpetually recruiting supply to the fistula which was responsible for the persistent neurologic deficit in our patient. Although these vascular lesions are rare, it is crucial that the diagnosis not be delayed for better neurologic outcome. It is imperative that cerebral and spinal angiography be performed without delay.

CONCLUSIONS: In patients who present with clinical symptoms of spinal cord syndrome who possess an MRI picture of vascular myelopathy and who exhibit negative spinal angiography, a four-vessel cerebral angiography should be undertaken, aiming at the recognition of an intracranial DAVF. Cerebral and spinal angiography without delay must be performed to instigate endovascular or surgical intervention for good neurologic outcome. Good outcome means complete cessation of the myelopathy