Surgical treatment of frontal lobe glial tumors. Current state of the problem. Part III: clinical, neurophysiological and surgical nuances

Frontal lobes are essential in making complex decisions and ensuring subtle social interactions. Importantly, patients with low-grade glial tumors often have no deficiency detected by standard neurological examination, but they may be completely unable to live a normal life in real world. The key principle in choosing surgical tactics for frontal lobe tumors is analysis of pathway with appropriate functional system adjacent to neoplasm and assessment of its functional safety before surgery. Research data on surgery for glioma near motor centers indicate that transient motor deficiency occurs in 30—90%, persistent deficiency — in 4—47% of cases. Intraoperative monitoring reduces the incidence of persistent deficiency (from 8.2% to 3.4%) and increases extent of resection (from 58% to 75%). To identify corticospinal tract, some studies demonstrate superiority of subcortical stimulation with monopolar probe and multipulse technique over bipolar stimulation. Importantly, complete disappearance of evoked motor potentials during transcranial stimulation is associated with high (up to 85%) risk of persistent motor deficit. New methods for «passive» mapping of speech function (corticocortical evoked potentials) reduce postoperative speech deficit. They are indicated in patients with contraindications for awake craniotomy.