Clinical features and outcomes of spinal cord arteriovenous malformations: comparison between nidus and fistulous types.

BACKGROUND AND PURPOSE As a result of the rarity of spinal cord arteriovenous malformations (AVM), there are only a few series available that describe clinical features, outcome after treatment, and natural history of these lesions. In this article, we aim to describe our experience with both nidus- and fistulous-type spinal cord AVMs. METHODS Forty-four consecutive patients with spinal cord AVMs were retrospectively reviewed. There were 26 patients with a nidus-type and 18 patients with a fistulous-type AVM. Treatments were performed with embolization (n=23), surgery (n=13), combined embolization-surgery (n=3), or conservative management (n=5). Clinical features, radiological findings, treatment results, and clinical outcomes were assessed. RESULTS Patients with nidus-type AVMs were younger at presentation and more often presented with hemorrhage, with a higher proportion of hematomyelia than fistulous-type AVMs (P<0.05). Progression of clinical presentation from hemorrhage to congestive myelopathy during follow-up was noted in 5 patients, all of which had AVMs of the nidus type. Complete obliteration could be achieved more often in the fistulous type (72%) than in the nidus type (27%). Improved or stable clinical status at last follow-up was noted in 100% of fistulous-type and 77% of nidus-type patients. Long-term clinical deterioration was noted in 6 of 26 patients with nidus-type (23%) AVMs and was related to recurrent bleeding (n=3) or progressive venous congestion (n=3). Overall rebleed rate after presentation with hemorrhage was 7 in 145.5 patient-years (4.8%/y) if the lesion was not treated, 3 in 102 patient-years (2.9%/y) after partial treatment, and 0 in 47.5 patient-years (0%) after complete treatment. CONCLUSIONS Nidus and fistulous spinal cord AVMs have different clinical features and obliteration rates, which may affect their long-term prognosis.