Awake surgery versus VEP in tumors of visual pathway: Case report

Verst, Silvia Mazzali; Melo, Mônica Nascimento de; Caivano, Andrea Sucena; Fonseca, Ubirajara Sabbag; Mathias, Luis Roberto; Alves, Tatiana Vilasboas

doi:10.1016/j.inat.2020.100675

Cited by 6 publications

(1 citation statement)

References 25 publications

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“…The most recognized method of continuous monitoring of VEPs is via transcranial recording with corkscrew scalp electrodes. Whilst these have shown good results, there is dispute about their correlation with post-operative deficits [19][20][21][22][23] , due to low spatial resolution, and the effect of anesthetic agents and brain manipulation on signal reproducibility 24 . Subdural strip electrodes use DCRs to enable cortical and subcortical mapping, to improve the accuracy of signals, and signal to noise ratio 25 .…”

Section: Discussionmentioning

confidence: 99%

Simultaneous Motor and Visual Intraoperative Neuromonitoring in Asleep Parietal Lobe Surgery: Dual Strip Technique

Rajashekar¹,

Lavrador²,

Ghimire³

et al. 2022

Preprint

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Background: The role played by the non-dominant parietal lobe in motor cognition, attention and spatial awareness networks has potentiated the use of awake surgery. When this is not feasible, asleep monitoring and mapping techniques should be used to achieve an onco-functional balance. Objective: This study aims to assess the feasibility of a dual-strip method to obtain direct cortical stimulation for continuous real-time cortical monitoring and subcortical mapping of motor and visual pathways simultaneously in parietal lobe tumour surgery. Methods: Single-centre prospective study between May’19-November’20 of patients with intrinsic non-dominant parietal-lobe tumours. Two subdural strips were used to simultaneously map and monitor motor and visual pathways. Results: Fifteen patients were included. With regards to motor function, a large proportion of patients had abnormal interhemispheric resting motor threshold ratio (iRMTr) (71.4%), abnormal Cortical Excitability Score (CES) (85.7%), close distance to the corticospinal tract – Lesion-To-Tract Distance (LTD) – 4.2mm, Cavity-To-Tract Distance (CTD) – 7mm and intraoperative subcortical distance - 6.4mm. Concerning visual function, the LTD and CTD for optic radiations (OR) were 0.5mm and 3.4mm, respectively; the mean intensity for positive subcortical stimulation of OR was 12mA±2.3mA and 5/6 patients with deterioration of VEPs>50% had persistent hemianopia and transgression of ORs. 12 patients remained stable, one patient had a de-novo transitory hemiparesis, and two showed improvements in motor symptoms. A higher iRMTr for lower limbs was related with a worse motor outcome (p=0.013) and a longer CTD to OR was directly related with a better visual outcome (p=0.041). At 2 weeks after hospital discharge, all patients were ambulatory at home and all proceeded to have oncological treatment. Conclusion: We propose motor and visual function boundaries for asleep surgery of intrinsic non-dominant parietal tumours. Pre-operative abnormal cortical excitability of the motor cortex, deterioration of the VEP recordings and CTD<2mm from the OR were related to poorer outcomes.

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