Acute Clinical Worsening after Steroid Administration in Cervical Myelitis May Reveal a Subdural Arteriovenous Fistula

Subdural arteriovenous fistula (SDAVF) is a rare condition characterized by clinical manifestations ranging from mild bilateral sensory deficits to quadriplegia. The diagnosis is often delayed due to unspecific neurological symptoms, initially diagnosed as polyneuropathy or myelopathy. The diagnosis can be delayed for as long as 1-15 years. The following report describes a cervical SDAVF case initially misdiagnosed as myelitis transversa and treated with intravenous steroids. A 56-year-old male presented with sensory deficits and mild leg and right arm weakness. Cervical MRI showed a central medullary hyperintense lesion with contrast enhancement. After metabolic, infectious, and malignant causes were excluded, myelitis transversa was presumed and the patient was treated intravenously with methylprednisolone. Shortly after that, he developed quadriplegia. Cervical MRI imaging showed engorged cervical perimedullary vessels, which were not visible on the initial MRI. The diagnosis was revised and a SDAVF identified. Prompt surgical treatment led to a complete recovery. The effect of intravenous steroids in SDAVF is controversial. Acute clinical worsening after steroid administration is previously reported in several publications; however, due to the paucity of clinical studies on SDAVF, this effect remains mostly overlooked or unknown. The findings in this patient support the causative relation between SDAVF clinical worsening and steroid administration. We propose that acute clinical worsening under steroids in patients initially diagnosed with myelitis should raise suspicion of an SDAVF.