Electrophysiologic Study of the Hemifacial Spasm

ABSTRACT

There has been controversy between compression of the facial nerve in the cerebellopontine recess and focal demyelination of the facial nerve on the pathogenesis of hemifacial spasm(HFS). To know the pathophysiology of HFS, we performed the facial nerve stimulation test and blink reflex test in 15 patients with HFS. And then we analyzed change of electrophysiologic findings after botulinum toxin in jection. We could not find any differences of latency between affected and unaffected side in facial nerve stimulation test(p>0.05). In the blink reflex test, there were prolonged R1 latency(p<0.01) and occurance of late response on the affected side. There has no change after botulinum toxin injection. These results suggest that there is no facial neuropathy and no electrophysiological evidence of dysfunction in the blink reflex system. Also, there may be two pathophysiologic lesions in HFS. compression and focal demyelination of the facial nerve. And we think that the botulinum toxin is no effect on facial nerve conduction itself.