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Acta Neurochirurgica

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Open Access 01-05-2020 | Vestibular Schwannoma | Original Article - Tumor - Schwannoma

TcMEP threshold change is superior to A-train detection when predicting facial nerve outcome in CPA tumour surgery

Authors: Tom Hendriks, Henricus P. M. Kunst, Maarten Huppelschoten, Jonne Doorduin, Mark Ter Laan

Published in: Acta Neurochirurgica | Issue 5/2020

Abstract

Object

Surgery of tumours in the cerebellopontine angle (CPA) can lead to loss of facial nerve function. Different methods of intra-operative nerve monitoring (IOM) (including free-running EMG, direct nerve stimulation and transcranial motor evoked potentials (TcMEP)) have been used to predict facial nerve outcome during surgery. Recent research has shown TcMEP threshold increase and the occurrence of A-trains on the EMG to have great potential in doing so. This study compares these two methods and correlates them to House-Brackmann (HB) scores post-op in patients with tumours in the cerebellopontine angle.

Method

Forty-three patients (one was operated twice) with large CPA tumours treated surgically in the Radboud University Medical Center between 2015 and 2019 were included in this study. During surgery, TcMEP threshold increases and A-train activity were measured. Because our treatment paradigm aims at facial nerve preservation (accepting residual tumour), TcMEP threshold increase of over 20 mA or occurrence of A-trains were considered as warning signs and used as a guide for terminating surgery. HB scores were measured post-op, at 6 weeks, 6 months and 1 year after surgery. Spearman’s correlation was calculated between the IOM-values and the HB scores for a homogeneous subgroup of 30 patients with vestibular schwannoma (VS) without neurofibromatosis type II (NF-II) and all patients collectively.

Results

TcMEP threshold was successfully measured in 39 (90.7%) procedures. In the homogeneous VS non-NFII group, we found a statistically significant moderate-to-strong correlation between TcMEP threshold increase and House Brackmann score immediately post-op, at 6 weeks, 6 months and 1 year after surgery (Spearman’s rho of 0.79 (p < 0.001), 0.74 (p < 0.001), 0.64 (p < 0.001) and 0.58 (p = 0.002), respectively). For A-trains, no correlation was found. Similar results were found when including all patients with CPA tumours. A threshold increase of < 20 mA was a predictor of good facial nerve outcome.

Conclusion

These results show that TcMEP threshold increases are strongly correlated to post-operative HB scores, while A-trains are not. This suggests TcMEP threshold increases can be a valuable predictor for facial nerve outcome in patients with large tumours when facial nerve preservation is prioritized over total resection. In this study, we found no use for A-trains to prevent facial nerve deficits.

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Title: TcMEP threshold change is superior to A-train detection when predicting facial nerve outcome in CPA tumour surgery
Authors: Tom Hendriks
Henricus P. M. Kunst
Maarten Huppelschoten
Jonne Doorduin
Mark Ter Laan
Publication date: 01-05-2020
Publisher: Springer Vienna
Keywords: Vestibular Schwannoma
Motor Evoked Potential
Vestibular Schwannoma
Motor Evoked Potential
Neuromonitoring
Published in: Acta Neurochirurgica / Issue 5/2020
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
DOI: https://doi.org/10.1007/s00701-020-04275-z

Keynote webinar | Spotlight on medication adherence

Springer Medicine

TcMEP threshold change is superior to A-train detection when predicting facial nerve outcome in CPA tumour surgery

Abstract

Object

Method

Results

Conclusion

Keynote webinar | Spotlight on medication adherence

Springer Medicine

Abstract

Object

Method

Results

Conclusion

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