Article
Facial nerve monitoring – a combination of EMG and MEP improves results
Monitoring des Nervus facialis – Eine Kombination aus EMG und MEP verbessert die Ergebnisse
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Published: | May 8, 2019 |
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Objective: Regarding facial nerve monitoring, criteria have been proposed for corticobulbar motor evoked potentials (MEP), for processed free-running EMG and for direct stimulation in terms of proximal/distal ratio in amplitudes. However, all three methods suffer from false positive monitoring results (monitoring criterion fulfilled, but no/little paresis). A direct comparison of the three methods in the same patients has never been demonstrated.
Methods: In 57 patients operated on for vestibular schwannoma, MEP and EMG monitoring were performed simultaneously; at the end of surgery, proximal/distal ratios and latency differences regarding direct nerve stimulation were also tested. The results were compared and also combined in order to objectify their predictive capacity. Several established and non-established monitoring-criteria were tested.
Results: Direct nerve stimulation failed to provide sufficient predictive capacity. Both MEP and EMG criteria on the other hand were useful in providing significant correlations between the extent of changes in potentials on the one hand and resulting deficits on the other hand (p=0.0037–0.029), but with the known weaknesses especially in terms of specificity. However, a combination of MEP and EMG provided improved results with highly significant correlations (p<0.0001).
Conclusion: A combination of EMG and MEP monitoring may improve the prognostic capacities of facial nerve monitoring in vestibular schwannoma surgery. Clinical routines for this should be developed. However, even with the improved results, there still remain false positive monitoring results.