A-train clusters and the intermedius nerve in vestibular schwannoma patients. Issue 5 (May 2019)

• Record Type: Journal Article
• Authors: Rampp, Stefan; Illert, Jörg; Krempler, Katja; Strauss, Christian; Prell, Julian
• Is Part Of: Clinical neurophysiology. Volume 130:Issue 5(2019:May)
• Page Start: 722
• Page End: 726
• Publication Date: 2019-05
• Subjects: A-train -- Vestibular schwannoma -- Intraoperative monitoring -- Intermedius nerve -- Electromyography; Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2019.02.014
• Languages: English
• ISSNs: 1388-2457

Abstract

Highlights: A-trains indicate facial nerve damage during intraoperative monitoring in vestibular schwannoma surgery. A separate intermedius nerve increases A-trains, partially occurring in cluster-like patterns. Intermedius nerve A-train clusters potentially confound intraoperative monitoring. Abstract: Objective: EMG "A-train" activity correlates with postoperative facial palsy after vestibular schwannoma (VS) surgery. An intermedius nerve separate from the facial nerve increases A-trains without significant impact on function. We investigate occurrence of A-train "clusters", A-trains over a majority of channels within a short time frame. Methods: Data from 217 patients with first surgery for VS were evaluated retrospectively. Continuous EMG recorded with 9 channels was evaluated for A-train patterns. "Clusters" of A-trains were identified, i.e. A-trains within 3 seconds over a majority of channels. Relation to a separate intermedius, tumor size and facial palsy was evaluated. Results: Correlations between A-trains and postoperative facial palsy were higher in patients without separate intermedius ( r = 0.562 versus r = 0.194). Clusters were identified in 107 patients (49.3%), separate intermedius in 109 (50.2%), with significant association of both ( p < 0.001, Chi-Square test). Excluding clusters slightly increased correlation of A-trains to facial nerve function. Conclusions: A-train clusters have limited relevance for predicting postoperative paresis. However, they should be regarded as warning signs, suggesting the presence of a separate intermedius nerve. Significance: A-train "clusters" are a sign of hyperactivity of the facial nerve due to a separate intermedius nerve and may confound intraoperative monitoring during VS surgery.