Compression of the C-2 root by a rare anomalous ectatic vertebral artery. Case report.

The authors report a symptomatic congenitally anomalous ectatic vertebral artery not passing through the transverse foramen of the atlas (C-1), but instead piercing the dura mater below the posterior arch of the C-1 in the atlantoaxial (C1-2) interlaminar space. This occurrence is exceptionally rare, but in this case it was uniquely associated with occipital neuralgia due to vascular compression of the C-2 root. Microvascular decompression was curative. Neuroradiological and surgical findings are presented and their implications discussed.