Methodology for intraoperatively eliciting motor evoked potentials in the vocal muscles by electrical stimulation of the corticobulbar tract

• Published in: Clinical neurophysiology Vol. 120; no. 2; pp. 336 - 341
• Main Authors: Deletis, Vedran, Fernandez-Conejero, Isabel, Ulkatan, Sedat, Costantino, Peter
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ireland Ltd 01-02-2009; Elsevier
• Subjects: Adult; Aged; Aged, 80 and over; Biological and medical sciences; Corticobulbar tract; Electric Stimulation - methods; Electrodiagnosis. Electric activity recording; Electromyography - methods; Evoked Potentials, Motor - physiology; Female; Fundamental and applied biological sciences. Psychology; Humans; Intraoperative monitoring; Investigative techniques, diagnostic techniques (general aspects); Laryngeal Muscles - physiopathology; Laryngeal nerve; Male; Medical sciences; MEPs; Middle Aged; Monitoring, Intraoperative; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Nervous system; Neurology; Pyramidal Tracts - surgery; Reaction Time; Transcranial electrical stimulation; Transcranial Magnetic Stimulation; Vertebrates: nervous system and sense organs; Vocal muscle; Young Adult; Intraoperative monitoring; Vocal muscle; Laryngeal nerve; Transcranial electrical stimulation; MEPs; Corticobulbar tract; Ability; Human; Methodology; Electrical stimulus; Electrophysiology; Intraoperative; Right hemisphere; Wire electrode; Neurophysiology; Ipsilateral; Strip electrode; Left hemisphere; Muscle; Motor evoked potential; Vagus nerve; Monitoring
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2008.11.013

Abstract Objective To establish a methodology for recording corticobulbar motor evoked potentials (CoMEPs) from vocal muscles after transcranial electrical stimulation (TES) and direct cortical stimulation (DCS). Methods Twenty-four patients were included in this study (22 for TES, 2 for DCS, 3 for TES plus DCS) that underwent different surgical procedures. We used two methods to elicit CoMEPs: (a) TES by stimulation over C3/Cz or C4/Cz and (b) DCS with a strip electrode placed over the primary motor area (M1) for laryngeal muscles. To record CoMEPs from vocal muscles we used two hook wire electrodes 76 μm of diameter passing through 27 gauge needle endotracheally placed in the vocal muscles after intubation. Results Recording of CoMEPs in the vocal muscles after TES was successfully performed in 22 patients. TES over the right or left hemisphere elicit responses bilaterally. The onset latencies for the right vocal muscle was 12.4 ± 3.1 ms (ipsilateral stimulation) and 12.7 ±2.2 ms (contralateral stimulation) while for the left vocal muscle, onset latency was 12.9 ± 2.3 ms (ipsilateral stimulation) and 14.1 ± 3.4 ms (contralateral stimulation). In five patients DCS elicited CoMEPs in right and left vocal muscle with latency of 16.6 ± 4.7 and 15.6 ± 3.7 ms, respectively. Conclusion The method to elicit and record CoMEPs in vocal muscles shows reliable results and adds one more tool in the armamentarium of intraoperative neurophysiology. Significance This method shows the ability to continuously monitor the functional integrity of corticobulbar pathways, vagal nucleus and laryngeal nerves.