Continuous subcortical language mapping in awake glioma surgery.

Area of Science:

• Neurosurgery
• Neuroscience
• Oncology

Background:

• Glioma resection requires precise navigation to preserve critical brain structures.
• Assessing proximity to language tracts during surgery is crucial for preventing deficits.
• Current mapping techniques have limitations in awake craniotomy settings.

Purpose of the Study:

• To evaluate the feasibility and efficacy of continuous monopolar short-train stimulation (STS) for intraoperative mapping of language tracts during awake glioma surgery.
• To determine if STS can reliably differentiate safe surgical margins from areas close to eloquent language pathways.

Main Methods:

• Prospective study involving 14 patients undergoing awake glioma resection.
• Continuous monopolar STS (3-Hz, 5 pulses, 250 Hz) applied via a suction probe tip during tumor removal.
• Language performance was tested during STS application at 70 subcortical locations.
• Comparison with bipolar Penfield stimulation (PS) as a gold standard for tract proximity.

Main Results:

• No language interference from STS at 28 locations (Group 1); PS was negative.
• Language interference with STS at ≥7.5 mA (Group 2; median 10 mA) occurred in 18 locations; PS was positive in only one.
• Language interference with STS at ≤5 mA (Group 3; median 5 mA) occurred in 24 locations; PS was significantly more often positive (15/24; p < 0.01).
• No seizures observed; temporary facial nerve stimulation occurred in five patients.

Conclusions:

• Continuous subcortical STS is a feasible technique for intraoperative language tract mapping in awake glioma surgery.
• Absence of STS-induced language interference or interference at ≥7.5 mA suggests a safe distance to language tracts, validated by PS.
• STS-induced language interference at ≤5 mA requires further investigation for consistent correlation with PS findings.