Introduction: Spinal vascular malformations can be classified in arteriovenous malformations, cavernomas, andcapillary telangiectasias. Arteriovenous malformations are the most common spinal vascular anomaly and may belocated intra- and/or perimedullary. According to their nidus type and hemodynamic flow patterns, they can bedifferentiated into fistulous, glomerular and juvenile categories. In our case, a hyperintense extradural masswas 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-tissuemass in the left L4 - S1 paravertebral region with homogeneous enhancement of contrast medium. Due toanother similar lesion in the lower ankle and additional cutaneous manifestations, the suspected diagnosiswas a systemic disease with neurinomas (e.g. Recklinghausen’s disease). To clear up the origin and type ofthis 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 malformationwas confirmed by a neuropathologist.

Conclusions: Completely extradural intraspinal arteriovenous malformations in the lumbar spine are extremelyrare. In magnetic resonance imaging they are often misinterpreted as a tumor. Arteriovenous malformationscan 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 intraspinalarteriovenous malformation should be considered as apossible diagnosis. Pre-operative angiography ormagnetic resonance imaging angiography can be used to verify the diagnosis.