Angiographically occult epidural arteriovenous fistula of the craniocervical junction.

Background: Spinal dural and intradural arteriovenous fistulas (AVFs) have been the subject of numerous reports but purely epidural AVFs causing venous congestion within the spinal cord are rare.

Case Description: We describe a patient with an exclusively epidural arteriovenous fistula and congestive myelopathy. There are three interesting features of this case as described below: 1) The presence of a purely epidural AVF of the cranio-cervical junction. According to our knowledge this is the first case of an AVF in this location. 2) The lesion was angiographically occult. This was probably because of the extremely slow flow of the fistula. 3) Despite the negative angiograms, exploratory surgery was conducted because of positive clinical and MR findings.

Conclusions: Epidural AVF/AVM of the foramen magnum should be considered in the differential diagnosis in patients with chronic myelopathy, even if cranial and spinal angiograms are negative. In these cases, we recommend that if clinical and radiological investigations strongly suggest the presence of an arteriovenous fistula, surgical exploration should be performed.