Hemifascial spasm is a repetitive uncontrolled contraction of one side of the facial muscles. Similar to Trigeminal Neuralgia, hemifacial spasm is also caused by compression of a cranial nerve.
In the case of trigeminal Neuralgia, the disease process is caused by compression of cranial nerve 5. In the case of hemifacial spasm, the disease process is caused by compression of cranial nerve 7. Thus, the microsurgical treatment of hemifacial spasm is very similar to microsurgical treatment of trigeminal neuralgia. In the microsurgical procedure for hemifacial spasm, a small sponge is introduced between the offending blood vessel and the 7th cranial nerve to relieve the facial contractions.