A 75-year-old woman developed low back pain, weakness of the lower extremities, and urinary retention. On day 7 after the onset of symptoms, she was brought to the emergency department of our hospital by an ambulance because of progressive weakness of both lower extremities. Spine MRI showed longitudinally extensive spinal cord lesion (LESCL) at the Th8-Th11 spinal cord level and flow voids around the lesions. Lumbar puncture revealed a normal opening pressure, yellowish appearance, pleocytosis with polymorphonuclear predominance, and decreased cerebrospinal fluid (CSF) glucose levels. Based on the rapidly progressing myelopathy, LESCL, and CSF findings, we initially diagnosed the patient with myelitis and administered acyclovir and high-dose intravenous immunoglobulin on day 7. Spine MRI with gadolinium-enhancement showed longitudinally extending flow voids of the thoracic cord, and digital subtraction arteriogram (DSA) revealed arteriovenous shunt on the dura with dilated and tortuous intradural veins. We finally diagnosed her with spinal dural arteriovenous fistula (SDAVF). Cases of SDAVF might be initially misdiagnosed as myelitis because of showing rapid progressive myelopathy, pleocytosis with polymorphonuclear predominance, and decreased CSF glucose levels. Lumbar puncture and steroid administration for the cases of SDAVF could aggravate the patient's neurological symptoms. Therefore, lumbar puncture and initiation of immunotherapy should be avoided until SDAVF is completely excluded in patients with suspected myelitis on spine MRI without gadolinium-enhancement, even if their neurological symptoms progress rapidly.
Keywords: immunotherapy; longitudinally extensive spinal cord lesion; lumbar puncture; polymorphonuclear predominance; spinal dural arteriovenous fistula.