Evaluation of the High-Frequency Monopolar Stimulation Technique for Mapping and Monitoring the Corticospinal Tract in Patients With Supratentorial Gliomas. A Proposal for Intraoperative Management Based on Neurophysiological Data Analysis in a Series of 92 Patients.
BACKGROUND
Intraoperative identification and preservation of the corticospinal tract is often necessary for glioma resection.


OBJECTIVE
To make a proposal for intraoperative management with the high-frequency monopolar stimulation technique for monitoring the corticospinal tract.


METHODS
Ninety-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.


RESULTS
Twenty-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.


CONCLUSIONS
Persistent 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.
Department of Neurosurgery, Hospital Universitari de Bellvitge, L'Hospitalet de Llobregat, Barcelona, Spain.
Gerard
G
Plans
Department of Neurophysiology, Hospital Universitari de Bellvitge, L'Hospitalet de Llobregat, Barcelona, Spain.
Isabel
I
Fernández-Conejero
Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute-IDIBELL, and Department of Basic Psychology, Campus Bellvitge, Universitat de Barcelona, L'Hos-pitalet de Llobregat, Barcelona, Spain.
Xavier
X
Rifà-Ros
Department of Neurosurgery, Hospital Universitari de Bellvitge, L'Hospitalet de Llobregat, Barcelona, Spain.
Alejandro
A
Fernández-Coello
Department of Neurosurgery, Hospital Universitari de Bellvitge, L'Hospitalet de Llobregat, Barcelona, Spain.
Aleix
A
Rosselló
Department of Neurosurgery, Hospital Universitari de Bellvitge, L'Hospitalet de Llobregat, Barcelona, Spain.
Andreu
A
Gabarrós
D000328:Adult; D000368:Aged; D001931:Brain Mapping / Q000379:methods / Q000592:standards*; D001932:Brain Neoplasms / Q000503:physiopathology / Q000601:surgery*; D046690:Deep Brain Stimulation / Q000379:methods / Q000592:standards*; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D005910:Glioma / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods / Q000592:standards*; D008297:Male; D008875:Middle Aged; D011712:Pyramidal Tracts / Q000502:physiology / Q000601:surgery*
Corticospinal tract; Glioma; High-frequency stimulation; Monitoring