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Analysis of venous drainage in three patients with extradural spinal arteriovenous fistulae at the craniovertebral junction with potentially benign implication

Background Extradural arteriovenous fistulae (AVFs) are vascular malformations that result from a direct connection between an extradural artery and vein, resulting in a high flow fistula that drains into the epidural venous system. Extradural AVFs may cause myelopathy when distended epidural veins compress the cord or when venous hypertension causes venous stasis within the spinal cord, and are uncommon causes of subarachnoid hemorrhage (SAH), although the presence of intracranial drainage is a risk factor for SAH. There are numerous reports of SAH and AVF with rostral intracranial venous drainage, implying an intradural drainage pathway. To our knowledge, a cervical spinal AVF at the craniovertebral junction (occurring between the occiput and C2) with exclusively extradural drainage and without a significant epidural component has not been described previously. Methods A retrospective review was performed identifying three patients treated at our hospital with cervical spinal AVF and extradural venous drainage. Results We present three cases of cervical spinal AVF with exclusive extradural venous drainage without accompanying intradural drainage—cranial or spinal. All three patients with exclusively extradural drainage have done well after 24 months of follow-up. The anatomical, clinical, and radiologic features are presented. Conclusions Patients with cervical AVF and exclusively extradural drainage pathways form a separate entity, representing a subset with a less ominous natural history.