Figure 4a.  (a) Lateral digital subtraction angiogram of the left vertebral artery reveals a reduction in the diameter of the artery extracranially (arrow). The intracranial vertebral and basilar arteries and the anterior inferior cerebellar artery appear normal (arrowheads). (b) Left anterior oblique digital subtraction angiogram shows an irregular narrowing of the vertebral artery between C2 and C1 (straight arrow). Curved arrow indicates a branch vessel feeding the anterior spinal artery. (c) Right anterior oblique digital subtraction angiogram again shows irregular narrowing of the dissected lumen (arrow) with a return to normal morphology intracranially.