Posterior Fossa Dural Arteriovenous Fistula As a Probable Cause of Congestive Myelopathy

A 62-year-old female suffered severe occipitalgia followed by progressive tetraparesis and bulbar symptoms, although tinnitus in the left ear persisting for more than 1 year resolved spontaneously after the onset. Cerebral magnetic resonance (MR) imaging revealed swelling in the lower brainstem, and cervical T_2-weighted MR imaging showed diffuse intramedullary hyperintensity in the medulla oblongata extending downward to the upper thoracic cord. Rim-like enhancement was localized at the C2 level after gadolinium administration. Extensive blood and cerebrospinal fluid examinations and whole body scintigraphy showed no indications of the underlying pathology. She underwent open biopsy for histological verification and decompressive maneuver to the cord. Sparse arterial distribution, and collapsed and partially thrombosed veins were recognized on the dorsal surface of the cord. Midline myelotomy yielded creamy fluid that proved to be necrotic tissue. Histological examination found the venous wall was thickened with lymphocytic infiltration. Her tetraparesis showed mild improvement postoperatively with marked resolution of the intramedullary hyperintensity on MR imaging. Postoperative cerebral angiography revealed a posterior fossa dural arteriovenous fistula (dAVF) fed by the left ascending pharyngeal and occipital arteries, with venous reflux to the ipsilateral inferior petrosal sinus. No venous drainage was found via the perimedullary vein. The dAVF was completely obliterated by transvenous coil embolization. We considered that the dAVF might have caused the congestive myelopathy. Decompressive maneuver may provide effective management for necrotizing myelopathy in selected cases.