Multimodal mapping and monitoring is beneficial during awake craniotomy for intra-cranial tumours: results of a dual centre retrospective study

Abstract

Background The combination of awake craniotomy with multimodal neurophysiological mapping and monitoring in intra-axial tumour resection is not well described, but may have theoretical benefits which we sought to investigate. Methods All patients undergoing awake craniotomy for tumour resection with cortical and/or subcortical stimulation together with one or more of electrocorticography (ECoG/EEG), motor or somatosensory evoked potentials were identified from the operative records of two surgeons at two centres over a 5 year period. Patient, operative and outcome data were collated. Statistical analysis was performed to evaluate factors predictive of intra-operative seizures and surgical outcomes. Results 83 patients with a median age 50 years (18–80 years) were included. 80% had gliomas (37% low grade) and 13% metastases. Cortical mapping was negative in 35% (language areas) and 24% (motor areas). Complete or near total resection was achieved in 80% with 5% severe long-term neurological deficits. Negative cortical mapping was combined with positive subcortical mapping in 42% with no significant difference in extent of resection rates to patients undergoing positive cortical mapping (p = 0.95). Awake mapping could not be completed in 14%, but with no compromise to extent of resection (p = 0.55) or complication rates (p = 0.09). Intraoperative seizures occurred in 11% and were significantly associated with intra-operative EEG spikes (p = 0.003). Conclusions Awake multi-modal monitoring is a safe and well tolerated technique. It provides preservation of extent of resection and clinical outcomes in cases of aborted awake craniotomy. Negative cortical mapping in combination with positive subcortical mapping was also shown to be safe, although not hitherto well described. Electrocorticography further enables the differentiation of seizure activity from true positive mapping, and the successful treatment of spikes prior to full clinical seizures occurring.