Application of intraoperative subcortical mapping by direct electrical stimulation for maximal safe resection of diffuse low-grade gliomas near eloquent areas

Abstract

Objective To report our experience of intraoperative subcortical napping by direct electrical stimulation in surgery of diffuse low-grade gliomas in supratentorial eloquent areas.Methods We conducted a retrospective analysis of clinical data of 57 patients with diffuse low-grade gliomas who were underwent awake craniotomy with the direct electrical stinulation for subcortical mapping of the eloquent fibers.The maximal resection of the tumors and minimal damage of the eloquent fibers were the surgical goal of all patients.Results The operation was stopped by individual functional boundaries as intra-operatively identification of the cortico-spinal pathways,or superior thalamic radiation,or language-related pathways in all patients.Post-operative MRI showed that 20 patients (35％) were achieved total resection,26(46％) subtotal and 11 partial(19％).11 patients (19％) had no postoperative deficits,while 46 patients (81％) had early post-operative neurologic deficits,including 15 patients with mild neurologic deficits,21 with moderate,and 10 with severe.Four patients experienced late post-operative neurologic deficits,including 3 patients with mild deficits,1 moderate.No one experienced severe late post -operative sequelae.Among 55 patients with pre-operative epilepsy,48 patients (87％) were seizure-free with taking anti-epilepsy drugs during seven days to three months after surgery,The frequency of post-surgical seizure attack in the remaining seven patients was decreased by 50％ compared with that of pre-operation.Conclusion Intraoperative subcortical mapping of the functional fibers by direct electrical stimulation under awake craniotomy allowed neurosurgeons to remove diffuse low-grade gliomas in supratentorial eloquent areas according to individual functional boundaries without increasing the late post-operative neurological deficits.However,frequent early postoperative neurological deficits often necessitated rehabilitation therapy. Key words: Glioma; Intraoperative neuroelectrophysiological monitoring; Stereotaxic techniques; Direct electrical stimulation; Awake craniotomy