Monitoring of facial muscle motor evoked potentials during microvascular decompression for hemifacial spasm: evidence of changes in motor neuron excitability
Bibliographic record
Abstract
OBJECT: Hemifacial spasm (HFS) is thought to be due to a hyperactive facial motor nucleus consequent to chronic neurovascular contact. The lateral spread (LS) response is presumed to reflect changes in facial motor neuron excitability. Facial muscle motor evoked potentials (MEPs) use the same efferent pathway as LS, therefore the authors speculated that these potentials should reflect differences consistent with changes at the facial motor nucleus level. METHODS: Monitoring of LS and bilateral facial MEP was performed in 10 consecutive patients undergoing MVD for HFS. Ipsilateral facial MEPs were monitored in 17 patients undergoing MVD for trigeminal neuralgia (TN). Latency, amplitude, and duration of the MEPs were compared before and after MVD. Following MVD the duration of ipsilateral MEPs decreased from 17.6 +/- 1.2 to 7.6 +/- 0.7 msec and their amplitude decreased from 269.9 +/- 66.3 to 76.5 +/- 26.2 microV (p < or = 0.01). These changes were consequent to the abolition of LS in eight of 10 patients and an approximately 50% reduction in two patients. The relationship between the reduction in MEPs and changes in LS was significant (p < 0.01). Control facial muscle MEPs (nonspastic side in patients with HFS and in those with TN) did not change significantly during the MVD procedure. Spasms were alleviated in nine of 10 patients, and there was no indication of facial nerve damage intraoperatively or postoperatively. CONCLUSIONS: Facial muscle MEPs represent a novel tool for studying the neurophysiological mechanisms of HFS in particular and monitoring the facial nerve in general. Data in this study support the hypothesis that the development of HFS and its alleviation with MVD are related to changes in facial motor nucleus activity.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".