Hemifacial spasm is a movement disorder characterized by spasms of the muscles innervated by the facial nerve (CN 7). The major clinical manifestation is involuntary unilateral clonic and/or tonic contractions of the muscles of facial expression. The most common cause is an ectatic blood vessel that compresses the facial nerve at the seventh nerve root exit zone in the cerebellopontine angle. As with essential blepharospasm, peripheral chemoderneravtion with botulinum toxin is the treatment of choice for most patients with hemifacial spasm.  For patients who do not experience adequate relief from botulinum toxin, microvascular decompression of the facial nerve at its exit zone may an appropriate option.