Hemifacial spasm associated with redundancy of the vertebral artery.

Hemifacial spasm is often caused by vascular compression of the 7th nerve in the cerebellopontine angle.Selective vertebral arteriography is valuable in identifying compression syndromes of vascular origin in the posterior fossa.Three examples of redundant, nonaneurysmal loops of the vertebral artery projecting into the cerebellopontine angle associated with hemifacial spasm are reported.