Facilitation of motor evoked potentials after tetanic peripheral nerve stimulation.

• Motor evoked potential amplitudes may be small and difficult to monitor during surgery in some patients. • Tetanic stimulation of peripheral nerves improves motor evoked potential amplitudes. • Tetanic stimulation can also be used in patient with myelopathy and peripheral neuropathy, with some cautions. Tetanic stimulation of a peripheral nerve prior to transcranial electrical stimulation (TES) may enhance motor evoked potential (MEP) amplitudes. The purpose of this study was to investigate the post-tetanic MEP (p-MEP) technique in improving MEP amplitudes. Conventional TES MEPs (c-MEP) and p-MEPs with left upper limb stimulation (p-MEP UL) or left lower limb stimulation (p-MEP LL) were performed in 26 patients. Bilateral hand and foot MEP amplitudes obtained with each protocol were compared. Subgroup comparisons were performed for myelopathy and peripheral neuropathy patients. Within-subject amplitude differences between c-MEP and each p-MEP technique were compared using a Wilcoxon test. The mean age of the patients was 52.7 years (range, 12–79 years). Overall, p-MEP UL resulted in MEP improvement in 25 of 26 (96%) patients, and p-MEP LL improved MEPs in 19 of 26 (73%) patients. The increase in MEP amplitudes were statistically significant in all muscle groups except left foot. Similar improvements were seen in the myelopathy group; in the neuropathy group, p-MEP UL produced similar results, but p-MEP LL did not. The p-MEP technique can improve MEP amplitudes, including in patients with myelopathy. In patients with peripheral neuropathy, the results were mixed. Tetanic stimulation can enhance intraoperative MEP amplitudes. [ABSTRACT FROM AUTHOR]