gms | German Medical Science

Objective: Neurosurgery of tumors adjacent to language and motor-associated cortical areas and subcortical pathways require intraoperative assessment. In awake patients, cortical and subcortical mapping are commonly performed with 60 Hz stimulation (Penfield-technique). Stimulation-related seizures, afterdischarges, delayed awakening or malcompliance interfere with successful testing and thus with the extent of surgical resection. Such mapping and monitoring with evoked potentials was considered helpful and introduced into a well-established setting of awake craniotomies.

Method: Multimodal intraoperative neuromonitoring, consisting of contralateral somatosensory evoked potentials (SEPs), transcranially and direct cortically elicited motor evoked potentials (MEPs) including monopolar mapping with the train-of-five-technique was implemented. The feasibility of combing multimodal monitoring and the Penfield technique as well as the influence on intraoperative decision-making were evaluated in a prospective study.

Results: 70 patients (55 ± 13 years, 37m) with frontal (17), pericentral (29), parietal (14) and temporal (12) lesions (astrocytoma (10), GBM (32), metastasis (16), other (12)) were analyzed. Monopolar stimulation for the motor cortex and corticospinal tract mapping was successful in all 70 cases. There were no serious side effects, despite the description of tingling pain during direct cortical stimulation. On the contrary, the Penfield technique did not evoke motor responses in 10 patients. 7/70 patients (10%) were not cooperative for language and motor testing. In one patient language testing was considered essential and surgery was prematurely terminated. In the remaining 6 patients, tumor resection was continued only with monopolar cortical and subcortical mapping as well as continuous monitoring of SEPs and MEPs.

Conclusions: Multimodal monitoring is feasible in awake craniotomies and was well tolerated. In cases of malcompliance and clinical deterioration, it allows for objective assessment of somatosensory and motor pathways. This permits the surgical tumor resection to proceed. In conclusion, the implementation of multimodal monitoring may be essential for pericentral surgery.