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A facial nerve study using transcranial magnetic paired stimulation
Akira Arai1, Takuya Yamakawa, Akiko Hagiwara
1Department of Otorhinolaryngology, School of Medicine, Juntendo University, 2-1-1, Hongo, Bunkyo-ku, Tokyo 113-8421, Japan. zvp11106@nifty.com
Auris, Nasus, Larynx
|August 21, 2003
Summary
Transcranial magnetic paired stimulation (TMPS) effectively evaluated facial nerve refractory periods and reflex pathways. This technique revealed significant amplitude decreases at short interstimulus intervals (ISIs) in healthy individuals.
Area of Science:
- Neuroscience
- Neurology
- Electrophysiology
Background:
- The refractory period of the facial nerve is crucial for understanding nerve signal transmission.
- Investigating facial nerve reflexes provides insights into neurological pathways involving the brainstem.
Purpose of the Study:
- To determine the refractory period of the facial nerve using transcranial magnetic paired stimulation (TMPS) with minimal interstimulus intervals (ISIs).
- To record and analyze the neurophysiological characteristics of long-latency responses elicited by TMPS.
Main Methods:
- Utilized TMPS with varying ISIs (0.9-2.1 ms) to measure facial nerve refractory periods in 30 healthy volunteers and 19 Bell's palsy patients.
- Recorded compound muscle action potentials (CMAPs) from the orbicularis oris muscle.
- Investigated facilitation and inhibition effects on long-latency responses using longer ISIs (40-1000 ms) in 10 healthy volunteers.
Main Results:
- A significant decrease in CMAP amplitude was observed in healthy subjects at ISIs below 1 ms.
- No response was detected in severe Bell's palsy cases (House-Brackmann Grade IV-V); partial responses were seen in Grade III.
- Long-latency responses were most strongly inhibited at an ISI of 80 ms.
Conclusions:
- TMPS is effective for assessing facial nerve refractory periods.
- The study successfully mapped facial nerve and trigeminal nerve reflex pathways, including those in the pons and medulla oblongata.