Division of Neurosurgery, University of Toronto, Ontario, Canada.
Object: Dural arteriovenous fistulas (AVFs) are a well-known pathoanatomical and clinical entity. Excluding bilateral involvement of the cavernous sinus, multiple dural AVFs are rare, with isolated reports in the literature. The additional risk associated with multiplicity is unknown, although it has been claimed that there is a greater risk of hemorrhage at presentation. In a group of 284 patients with dural AVFs consecutively treated at a single center, the occurrence of multiplicity is investigated and its risk factors for hemorrhage are identified.
Methods: Among the 284 patients with both cranial and spinal dural AVFs, 20 patients with multiple fistulas were found. Nineteen (8.1%) of 235 patients with cranial AVFs had multiple cranial fistulas, and one (2%) of 49 patients with spinal AVFs harbored two spinal fistulas. Twelve patients were found to have a lesion at two separate sites, seven patients had them at three locations, and one patient had four fistulas, each at a different site. In the subgroup with multiple AVFs the percentage of hemorrhage at presentation was three times higher than in the entire group (p = 0.01). Cortical venous drainage in cranial fistulas was present in 84% of patients with multiple lesions compared with 46% of patients with solitary lesions (p < 0.005).
Conclusions: Multiple dural AVFs are not rare. In this group of 284 patients it was found in 8.1% of all patients with cranial dural AVFs. Multiplicity was associated with a higher percentage of cortical venous drainage, a pattern of drainage reportedly yielding a higher risk for hemorrhage.