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Hemilingual spasm: pathophysiology
Aage R Møller1, Leisha L Osburn, Aaron A Cohen-Gadol
1School of Behavioral and Brain Sciences, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, USA. amoller@utdallas.edu
Neuroscience Letters
|June 13, 2009
Summary
This study reveals that hemilingual spasm, a tongue movement disorder, stems from hyperactivity of the hypoglossal motonucleus. Electromyography (EMG) findings during surgery support this, showing responses similar to hemifacial spasm.
Area of Science:
- Neurology
- Neurophysiology
- Neurosurgery
Background:
- Hemilingual spasm is a rare cranial nerve hyperactivity syndrome affecting the tongue.
- The exact neurophysiological mechanisms underlying hemilingual spasm remain unclear.
- Hemifacial spasm (HFS) involves facial nerve hyperactivity, characterized by specific electromyographic (EMG) findings.
Purpose of the Study:
- To investigate the role of the hypoglossal motonucleus in hemilingual spasm.
- To characterize the electrophysiological findings in patients undergoing surgery for hemilingual spasm.
- To compare the EMG response in hemilingual spasm with that of hemifacial spasm.
Main Methods:
- Electromyography (EMG) was used to record tongue muscle activity during microvascular decompression surgery.
- Transcranial stimulation was applied to elicit responses.
- The effect of vascular decompression on EMG responses was observed.
Main Results:
- A delayed EMG response was elicited from the tongue following transcranial stimulation.
- This response had a latency of ~40 ms and duration of ~50 ms.
- The abnormal EMG response disappeared after relieving pressure on the hypoglossal nerve root, similar to findings in HFS.
Conclusions:
- The findings suggest that hemilingual spasm is caused by hyperactivity of the hypoglossal motonucleus.
- The electrophysiological characteristics of hemilingual spasm resemble those of hemifacial spasm.
- This study provides novel electrophysiological evidence for the pathophysiology of hemilingual spasm.
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