Intra-operative Central Sulcus Localization Using Median Nerve Somatosensory Evoked Potentials via 1x4 Subdural Strip: A Single-center Experience
Geronimo Pacheco Aispuro1, Saeideh Salehizadeh1, Kenneth Matsko1, Michael Windom1, Tiffany Hodges2, Neel Fotedar1
1Epilepsy Center, Neurological Institute, University Hospitals Cleveland Medical Center, 2Department of Neurosurgery, University Hospitals, Cleveland Medical Center
Objective:

To report the safety and efficacy of intra-operative central sulcus (CS) mapping using a 1x4 subdural strip.

Background:
Intra-operative CS mapping is critical for precise localization of the primary motor cortex during neurosurgical procedures. Median nerve somatosensory evoked potential’s phase reversal technique (PRT) is a well-established and reliable method to identify the CS. Usually, an eight-contact subdural grid is used, but a 1x4-electrode strip could offer improved maneuverability while maintaining accuracy.
Design/Methods:
We performed a retrospective analysis of 15 patients who underwent intra-op CS mapping during tumor resection. We analyzed the major waveforms (N20, P20, and P25) on both surface and subdural electrodes and compared their latencies and their spatial relationships. We also reviewed pre- and post-op neurological exams to assess the clinical outcome.
Results:

The N20/P20 waveform was recorded on scalp and subdural electrodes in 86.7% cases. P25 waveform was recorded on the scalp and subdural electrodes in 100% and 93.3% cases, respectively. Overall, CS was successfully identified in 86.7% cases with the PRT technique. The N20 and P20 peaks were not aligned in any case, and the N20 peak consistently preceded the P20 by ~2.1ms. N20 latency difference between scalp and subdural electrodes was ~1.5ms. The P25 waveform was clearly seen in the electrodes, showing the N20 peak in 93% cases. CS localization took an average of 313.15±306.15 seconds. Tumor location was primarily frontal (53%), with 26% multilobar, 13% parietal, and 7% temporal. Only one patient experienced an intra-op seizure unrelated to CS mapping, and there were no other complications. In 91% cases, no new or worsening neurological deficits were noted up to one month follow-up.

Conclusions:

Our study demonstrates a safe, reliable, and efficient method to localize the CS using a 1x4 subdural strip. Our findings are in agreement with the tangential-radial dipole model of median nerve cortical somatosensory evoked potentials.

 

10.1212/WNL.0000000000204747