Completely extradural intraspinal arteriovenous malformation in the lumbar spine: a case report.

Introduction: Spinal vascular malformations can be classified in arteriovenous malformations, cavernomas, and capillary telangiectasias. Arteriovenous malformations are the most common spinal vascular anomaly and may be located intra- and/or perimedullary. According to their nidus type and hemodynamic flow patterns, they can be differentiated into fistulous, glomerular and juvenile categories. In our case, a hyperintense extradural mass was misinterpreted as a neurinoma. The histological analysis revealed typical signs of an arteriovenous malformation.

Case Presentation: A 57-year-old Caucasian woman presented with back pain and hypesthesia in digiti two to four of her left foot. Magnetic resonance imaging showed a long-segment intraspinal extradural soft-tissue mass in the left L4 - S1 paravertebral region with homogeneous enhancement of contrast medium. Due to another similar lesion in the lower ankle and additional cutaneous manifestations, the suspected diagnosis was a systemic disease with neurinomas (e.g. Recklinghausen's disease). To clear up the origin and type of this lesion exploratory surgery with a hemilaminectomy of L5 was performed. This showed abnormally arterialized, dilated, and tortuous vessels. After complete resection, the intra-operative impression of an arteriovenous malformation was confirmed by a neuropathologist.

Conclusions: Completely extradural intraspinal arteriovenous malformations in the lumbar spine are extremely rare. In magnetic resonance imaging they are often misinterpreted as a tumor. Arteriovenous malformations can cause compression and venous congestion, or mask symptoms like a spinal disk herniation.In cases presenting with these symptoms and magnetic resonance imaging findings, an extradural intraspinal arteriovenous malformation should be considered as a possible diagnosis. Pre-operative angiography or magnetic resonance imaging angiography can be used to verify the diagnosis.