Abstract
The authors describe the case of a 29 year old man with a negative prior history who developed a left sided hemifacial tic following a low speed motor vehicle crash. Subsequent MRI and MRA imaging revealed an absent left posterior inferior cerebellar artery, along with an enlarged anterior inferior cerebellar artery in the region of the root entry zone (REZ) of cranial nerves VII and VIII. It was hypothesized that the moderate level of peak head acceleration (12–15 g or more) was sufficient to approximate the vascular loop to the REZ of VII and VIII. The patient was treated successfully (albeit temporarily) with injections of Botox.