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

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 facia...

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Bibliographic Details
Published in:Acta neurochirurgica 2020-05, Vol.162 (5), p.1197-1203
Main Authors: Hendriks, Tom, Kunst, Henricus P. M., Huppelschoten, Maarten, Doorduin, Jonne, Ter Laan, Mark
Format: Article
Language:English
Subjects:
Electromyography
Facial nerve
Genetic disorders
Interventional Radiology
Medicine
Medicine & Public Health
Minimally Invasive Surgery
Motor evoked potentials
Neurofibromatosis
Neurological disorders
Neurology
Neuroradiology
Neurosurgery
Original - Tumor - Schwannoma
Original Article - Tumor - Schwannoma
Patients
Preservation
Schwann cells
Statistical analysis
Surgery
Surgical Orthopedics
Tumor – Schwannoma
Tumors
Vestibular system
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Summary: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  
ISSN:0001-6268
0942-0940
DOI:10.1007/s00701-020-04275-z