Intraoperative spinal cord monitoring using low intensity transcranial stimulation to remove post-activation depression of the H-reflex. Issue 10 (October 2016)

• Record Type: Journal Article
• Authors: Andrews, Jennifer C.; Stein, Richard B.; Jones, Kelvin E.; Hedden, Douglas M.; Mahood, James K.; Moreau, Marc J.; Huang, Eric M.; Roy, François D.
• Is Part Of: Clinical neurophysiology. Volume 127:Issue 10(2016:Oct.)
• Page Start: 3378
• Page End: 3384
• Publication Date: 2016-10
• Subjects: Motor evoked potential -- H-reflex -- Post-activation depression -- Scoliosis -- Intraoperative monitoring -- Spinal cord; Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2016.08.007
• Languages: English
• ISSNs: 1388-2457

Abstract

Highlights: A spinal cord monitoring technique was tested during spinal deformity correction surgery. Low intensity TES removed post-activation depression of the H-reflex in 20/20 patients. The interaction did not diminish with time and produced minimal movement within the surgical field. Abstract: Objective: To investigate whether low intensity transcranial electrical stimulation (TES) can be used to condition post-activation depression of the H-reflex and simultaneously monitor the integrity of spinal motor pathways during spinal deformity correction surgery. Methods: In 20 pediatric patients undergoing corrective surgery for spinal deformity, post-activation depression of the medial gastrocnemius H-reflex was initiated by delivering two pulses 50–125 ms apart, and the second H-reflex was conditioned by TES. Results: Low intensity TES caused no visible shoulder or trunk movements during 19/20 procedures and the stimulation reduced post-activation depression of the H-reflex. The interaction was present in 20/20 patients and did not diminish throughout the surgical period. In one case, the conditioning effect was lost within minutes of the disappearance of the lower extremity motor evoked potentials. Conclusion: Post-activation depression was used to detect the arrival of a subthreshold motor evoked potential at the lower motor neuron. The interaction produced minimal movement within the surgical field and remained stable throughout the surgical period. Significance: This is the first use of post-activation depression during intraoperative neurophysiological monitoring to directly assess the integrity of descending spinal motor pathways.