A-train [Neurosurgery Wiki]

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====== A-train ======

[[EMG]] "A-[[train]]" activity correlates with postoperative [[facial palsy]] after [[vestibular schwannoma surgery]]. An [[Intermediate nerve]] separate from the [[facial nerve]] increases A-trains without significant impact on function. Rampp et al., investigated the occurrence of A-train "clusters", A-trains over a majority of channels within a short time frame.

Data from 217 patients with first surgery for [[vestibular schwannoma]] (VS) were evaluated retrospectively. Continuous EMG recorded with 9 channels was evaluated for A-train patterns. "[[Cluster]]s" 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.

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.

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.

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
((Rampp S, Illert J, Krempler K, Strauss C, Prell J. A-train clusters and the
intermedius nerve in vestibular schwannoma patients. Clin Neurophysiol. 2019 Mar 
15;130(5):722-726. doi: 10.1016/j.clinph.2019.02.014. [Epub ahead of print]
PubMed PMID: 30901633.
)).