A real-time monitoring system for the facial nerve.
OBJECTIVE
Damage to the facial nerve during surgery in the cerebellopontine angle is indicated by A-trains, a specific electromyogram pattern. These A-trains can be quantified by the parameter "traintime," which is reliably correlated with postoperative functional outcome. The system presented was designed to monitor traintime in real-time.


METHODS
A dedicated hardware and software platform for automated continuous analysis of the intraoperative facial nerve electromyogram was specifically designed. The automatic detection of A-trains is performed by a software algorithm for real-time analysis of nonstationary biosignals. The system was evaluated in a series of 30 patients operated on for vestibular schwannoma.


RESULTS
A-trains can be detected and measured automatically by the described method for real-time analysis. Traintime is monitored continuously via a graphic display and is shown as an absolute numeric value during the operation. It is an expression of overall, cumulated length of A-trains in a given channel; a high correlation between traintime as measured by real-time analysis and functional outcome immediately after the operation (Spearman correlation coefficient [rho] = 0.664, P < .001) and in long-term outcome (rho = 0.631, P < .001) was observed.


CONCLUSIONS
Automated real-time analysis of the intraoperative facial nerve electromyogram is the first technique capable of reliable continuous real-time monitoring. It can critically contribute to the estimation of functional outcome during the course of the operative procedure.
Prell
Julian
J
Department of Neurosurgery, University of Halle, Halle, Germany. julian.prell@medizin.uni-halle.de
Rachinger
Jens
J
Scheller
Christian
C
Alfieri
Alex
A
Strauss
Christian
C
Rampp
Stefan
S
D000328:Adult; D000368:Aged; D004576:Electromyography / Q000295:instrumentation / Q000379:methods*; D004582:Electronics, Medical / Q000379:methods; D005154:Facial Nerve / Q000033:anatomy & histology / Q000502:physiology* / Q000601:surgery*; D020220:Facial Nerve Injuries / Q000209:etiology / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007431:Intraoperative Complications / Q000209:etiology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods*; D019635:Neurosurgical Procedures / Q000009:adverse effects / Q000379:methods; D011446:Prospective Studies; D012815:Signal Processing, Computer-Assisted; D012984:Software; D055815:Young Adult