Abstract
Background
Careful examination of motor-evoked potential (MEP) findings is critical to the safety of intraoperative neuromonitoring during neurosurgery. We reviewed the intraoperative MEP findings in a pediatric patient who had undergone hemispherotomy for refractory epilepsy.
Case description
The patient was a 4-year-and-2-month-old boy with extensive right cerebral hemisphere, drug-resistant epilepsy, left upper and lower extremity paralysis, and cognitive impairment. We examined intraoperative MEP results both before and after hemispherotomy. Post-hemispherotomy and MEPs were successfully elicited through transcranial electrical stimulation (TES) but not via direct cortical stimulation on the right side. Furthermore, TES on the right side, following hemispherotomy, led to a reduction in the MEP amplification effect resulting from tetanic stimulation of the left unilateral median and tibial nerves. Conversely, we observed the effects of MEP amplification during TES on the left side after tetanic stimulation of these nerves. Postoperatively, the patient underwent magnetic resonance imaging and electroencephalogram examinations, confirming the anatomical and electrophysiological completeness of the dissection. Notably, the seizures disappeared, and no apparent complications were observed.
Conclusion
Collectively, our findings suggest that TES can still activate deep structures and elicit MEPs, even in cases where the corticospinal connections to the posterior limb of the internal capsule are entirely severed. Thalamo-cortical interactions may affect the MEP amplification, observed during tetanic stimulation. Injury to the corticospinal tracts of the white matter may be obscured on conventional MEP findings; however, it may be identified by MEP changes in tetanic stimulation.
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Data availability
All data generated or analyzed during this study are included in this published article and its supplementary information files.
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R.S. designed the study, the main conceptual ideas, and the proof outline. R.S. and T.T. collected the data. R.S. and K.T. aided in interpreting the results and worked on the manuscript. I.N. supervised the project. R.S. wrote the manuscript with support from Y.P. and I.N. All authors discussed the results and commented on the manuscript.
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Sasaki, R., Tamura, K., Takatani, T. et al. Intraoperative motor-evoked potential with tetanic stimulation changes pre- and post-hemispherotomy. Childs Nerv Syst 40, 563–567 (2024). https://doi.org/10.1007/s00381-023-06170-1
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DOI: https://doi.org/10.1007/s00381-023-06170-1