• Gerard Plans, Isabel Fernández-Conejero, Xavier Rifà-Ros, Alejandro Fernández-Coello, Aleix Rosselló, and Andreu Gabarrós.
• Department of Neurosurgery, Hospital Universitari de Bellvitge, L'Hospitalet de Llobregat, Barcelona, Spain.
• Neurosurgery. 2017 Oct 1; 81 (4): 585-594.

BackgroundIntraoperative identification and preservation of the corticospinal tract is often necessary for glioma resection.ObjectiveTo make a proposal for intraoperative management with the high-frequency monopolar stimulation technique for monitoring the corticospinal tract.MethodsNinety-two patients operated on with the assistance of the high-frequency monopolar stimulation. Clinical and neurophysiological data have been related with the motor status at 3 months to establish prognostic factors of motor deterioration.ResultsTwenty-one patients (22.8%) presented intraoperative alterations in motor-evoked potentials (MEPs). Twelve (13%) presented an increment in the MEP threshold ≥5 mA (no deficit at 3 months). Two (2.2%) presented an MEP amplitude reduction >50% (100% deficit at 3 months). Seven (7.6%) had an intraoperative MEP loss (80% deficit at 3 months). Subcortical stimulation was positive in 75 patients (81.5%). Eighty-five patients were available for the analysis at 3 months. Fourteen presented new deficits (16.5%). Among them, 5 presented a deficit in nonmonitored muscles (5.9%) and 1 presented a new deficit not detected intraoperatively. The combination of patients with preoperative motor deficits, MEP deterioration, or loss and intensity of subcortical stimulation ≤3 mA showed the highest sensitivity and specificity in the prediction of new deficits.ConclusionsPersistent MEP loss or deterioration is associated with a high probability of new deficits. It seems recommendable to stop the subcortical resection before obtaining a subcortical MEP threshold at 3 mA especially in patients with preoperative motor deficits. A careful selection of muscles for the registration of MEPs is mandatory to avoid deficits in nonmonitored muscles.Copyright © 2016 by the Congress of Neurological Surgeons

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