[Hemimasticatory muscle spasm: an electromyogram analysis].
OBJECTIVE: To investigate the usefulness of electromyogram (EMG) in the diagnosis of the patients with hemimasticatory spasm (HMS). METHODS: Four cases with HMS were reported. All the 4 patients were undertaken needle and surface electrode EMG examination. RESULTS: Needle electrode EMG of the 4 patients with HMS showed grouped potentials synchronously with the onset of the spasm, which indicated abnormal excitatory electrical activities of the trigeminal nerve resulting in involuntary masticatory muscle movements. CONCLUSION: It is very important to use EMG for the diagnosis of HMS.
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