We adopted the asleep-awake-asleep protocol for awake craniotomy with direct brain stimulation, and tumor removal was performed on all 80 patients. After removing the bone flap, the patient was awakened, and cortical mapping was used to identify language and motor areas. The StealthStation S7 neuronavigation (Medtronic Navigation) was applied in each case to plan the surgical incision and identify tumor margins related to brain sulcal and gyral surface structures. Intraoperative ultrasound was also used to help distinguish the tumor boundaries. Before the brain shifts, numerical and letter tags were placed along the cortical tumor margins.
A biphasic current (pulse frequency 60 Hz; single pulse duration 0.5 msec) was delivered through a bipolar stimulator with a 5 mm interelectrode distance for cortical stimulation. The initial setting was 1 mA, gradually increasing the amplitude in 0.5-1 mA increments until reproducible response (motor or sensory function) was obtained or discharge potentials were detected (baseline 1 mA, maximum 8 mA). Stimulation was applied for 4 s at the indicated areas, with a pause of 2-4 s between stimulations. Cortical and subcortical regions were identified using a similar stimulation protocol.
Sensorimotor mapping was first performed to confirm the positive responses (movement and/or paresthesia). Stimulations were repeated at least three times to confirm the positive sites. A negative sensorimotor area was also indicated when no response occurred in the area of interest.
For language mapping, the patient was asked to perform three verbal tasks: counting (regular rhythm, from 1 to 10, repetitively), picture naming (DO80) and word-reading task to identify the essential cortical sites which might be inhibited by stimulation. During the picture naming task, the patient was asked to read a short phrase in Chinese as “this is a ……” before naming each picture to check whether seizures were generated and induced speech arrest if the patient could not name the picture successfully. During the word-reading task, the patient was asked to read Chinese words presented on the computer screen. The duration of each stimulation was also about 4 s. Between each actual stimulus interval, at least one picture was presented without stimulation, and no site was stimulated twice in succession. The types of language disturbances (speech arrest, dysarthria, phonetic/phonemic/semantic paraphasia, anomia, and alexia) found intraoperatively were classified by neuropsychological experts in our department.
By applying the same stimulation parameters, the glioma was removed with alternating resection and electrostimulation for subcortical functional mapping. The patient continuously performed the above tasks throughout glioma resection.
A biphasic current (pulse frequency 60 Hz; single pulse duration 0.5 msec) was delivered through a bipolar stimulator with a 5 mm interelectrode distance for cortical stimulation. The initial setting was 1 mA, gradually increasing the amplitude in 0.5-1 mA increments until reproducible response (motor or sensory function) was obtained or discharge potentials were detected (baseline 1 mA, maximum 8 mA). Stimulation was applied for 4 s at the indicated areas, with a pause of 2-4 s between stimulations. Cortical and subcortical regions were identified using a similar stimulation protocol.
Sensorimotor mapping was first performed to confirm the positive responses (movement and/or paresthesia). Stimulations were repeated at least three times to confirm the positive sites. A negative sensorimotor area was also indicated when no response occurred in the area of interest.
For language mapping, the patient was asked to perform three verbal tasks: counting (regular rhythm, from 1 to 10, repetitively), picture naming (DO80) and word-reading task to identify the essential cortical sites which might be inhibited by stimulation. During the picture naming task, the patient was asked to read a short phrase in Chinese as “this is a ……” before naming each picture to check whether seizures were generated and induced speech arrest if the patient could not name the picture successfully. During the word-reading task, the patient was asked to read Chinese words presented on the computer screen. The duration of each stimulation was also about 4 s. Between each actual stimulus interval, at least one picture was presented without stimulation, and no site was stimulated twice in succession. The types of language disturbances (speech arrest, dysarthria, phonetic/phonemic/semantic paraphasia, anomia, and alexia) found intraoperatively were classified by neuropsychological experts in our department.
By applying the same stimulation parameters, the glioma was removed with alternating resection and electrostimulation for subcortical functional mapping. The patient continuously performed the above tasks throughout glioma resection.
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