Artikel
A new bilateral motor threshold criterion for corticobulbar MEP has superior predictive value than previously used criteria
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Autoren
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Tobias Greve
- Klinikum der Universität München, Neurochirurgische Klinik und Poliklinik, München, Deutschland
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Liang Wang
- Beijing Tiantan Hospital, Department of Neurosurgery, Beijing, China, Volksrepublik
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Jörg-Christian Tonn
- Klinikum der Universität München, Neurochirurgische Klinik und Poliklinik, München, Deutschland
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Christian Schichor
- Klinikum der Universität München, Neurochirurgische Klinik und Poliklinik, München, Deutschland
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Andrea Szelényi
- Klinikum der Universität München, Neurochirurgische Klinik und Poliklinik, München, Deutschland
| Veröffentlicht: | 18. Juni 2018 |
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Gliederung
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Objective: Intraoperatively, facial nerve (FN) function is assessed with corticobulbar Motor Evoked Potentials (FN-coMEP). MEP-amplitude decrement and increase in motor threshold (MT) serve as warning criteria. A novel threshold criterion for extremity muscle MEP compares final-to-baseline motor threshold levels (BFB-MT) between the operated versus non-operated side. We applied BFB-MT for FN-coMEP with regard to postoperative FN-function.
Methods: 79 patients (45f;48±16yrs.,68% vestibular schwannoma) undergoing cerebellopontine angle tumor surgery were analysed. FN-function was assessed with the House-Brackmann score (HB) pre- and postoperatively at day 1 (d1), 7 (d7), 3 months (3m) and grouped in mild (HB score increase ≤1) or marked deterioration (HB score increase ≥2). FN-coMEP were elicited with anodal transcranial electric stimulation at C4;C3 referenced to Cz, and recorded from oris and mentalis muscles. A BFB-MT difference ≥20% (operated vs. non-operated side) was considered significant. MT-increase of ≥20mA and amplitude decrement ≥50% on the operated side served as reference criteria. FN function was correlated to all 3 criteria.
Results: At d1, 22% of patients (17/79) showed mild HB deterioration, 27% (21/79) marked. At d7, 25% (20/79) showed mild and 16% (13/79) marked deterioration. At 3m follow-up (available in 68 patients), 94% showed recovery (64/68). Only 4/68 (6%) patients showed residual marked FN function deterioration.
FN-coMEP were obtained in 95% cases (75/79). Changes according to BFB-MT (35±17mA) occurred in 17 patients, 16 of these patients suffered a marked deterioration of FN function at d1.
BFB-MT correlated significantly with FN function at d1 and d7. The correlation was stronger using the BFB-MT (Spearman correlation: d1: p=0.726; d7: p=0.559; 3m: p=0.265) compared to absolute threshold increase ≥20mA (Spearman correlation: d1: p=0.675; d7: p=0.528; 3m: p=0.275) and amplitude reduction ≥50% (Spearman correlation: d1: p=0.305; d7: p=0.378; 3m: p=0.118).
Conclusion: An increase of BFB-MT ≥20% between the operated vs. non-operated side serves as a better predicator for postoperative FN function than absolute mA increase and amplitude reduction. Further studies have to validate this criterion intraoperatively for its real time applicability.
