Intraoperative direct electrocortical stimulation for glioma surgery

see also Awake surgery for glioma.

see also Resting-state functional magnetic resonance for glioma surgery.

Stimulation-induced seizures (SISs) are rare but serious events during electrocortical stimulation (ECS) mapping. SISs are most common when mapping the frontal lobe. Greater stimulation current is not associated with the identification of more cortical functional sites during glioma surgery 1).

Glioma surgery represents a significant advance with respect to improving resection rates using new surgical techniques, including intraoperative functional mappingmonitoring, and imaging. Functional mapping under awake craniotomy can be used to detect individual eloquent tissues of speech and/or motor functions in order to prevent unexpected deficits and promote extensive resection. In addition, monitoring the patient’s neurological findings during resection is also very useful for maximizing the removal rate and minimizing deficits by alarming that the touched area is close to eloquent regions and fibers. Assessing several types of evoked potentials, including motor evoked potentials (MEPs), sensory evoked potentials (SEPs), and visual evoked potentials (VEPs), is also helpful for performing surgical monitoring in patients under general anesthesia (GA) 2).

The greater extent of resection (EOR) of low-grade gliomas is associated with improved survival. Proximity to eloquent cortical regions often limits resectability and elevates the risk of surgery-related deficits. Therefore, functional localization of eloquent cortex or subcortical fiber tracts can enhance the EOR and functional outcomeImaging techniques such as functional MRI and diffusion tensor imaging fiber tracking, and neurophysiological methods like navigated transcranial magnetic stimulation and magnetoencephalography, make it possible to identify eloquent areas prior to resective surgery and to tailor indication and surgical approach but also to assess the surgical risk. Intraoperative monitoring with direct cortical stimulation and subcortical stimulation enables surgeons to preserve essential functional tissue during surgery. Through tailored, pre-and intraoperative mapping and monitoring the EOR can be maximized, with reduced rates of surgery-related deficits 3).

As the most accurate and reliable method of brain functional area positioning, Intraoperative direct electrocortical stimulation is able to determine in real-time the parts of the brain necessary for such functions as movementsensationlanguage, and even memory. A meta-analysis suggested that it could also improve the degree of resection of glioma while reducing the incidence of permanent neurological dysfunction 4).

Findings suggest that surgeons using Intraoperative direct electrocortical stimulation and awake craniotomy during their resections of high-grade glioma in eloquent areas experienced better surgical outcomes: a significantly longer overall postoperative survival, a lower rate of postoperative complications, and a higher percentage of GTR 5).

Resting-state functional magnetic resonance imaging likely reflects similar neural information as detected with intraoperative direct electrocortical stimulation (DES), but in its current form does not reach the spatial resolution of DES. 6).


Muster RH, Young JS, Woo PYM, Morshed RA, Warrier G, Kakaizada S, Molinaro AM, Berger MS, Hervey-Jumper SL. The Relationship Between Stimulation Current and Functional Site Localization During Brain Mapping. Neurosurgery. 2021 May 13;88(6):1043-1050. doi: 10.1093/neuros/nyaa364. PMID: 33289525; PMCID: PMC8117445.

Saito T, Muragaki Y, Maruyama T, Tamura M, Nitta M, Okada Y. Intraoperative Functional Mapping and Monitoring during Glioma Surgery. Neurol Med Chir (Tokyo). 2015;55 Suppl 1:1-13. PMID: 26236798.

Ottenhausen M, Krieg SM, Meyer B, Ringel F. Functional preoperative and intraoperative mapping and monitoring: increasing safety and efficacy in glioma surgery. Neurosurg Focus. 2015 Jan;38(1):E3. doi: 10.3171/2014.10.FOCUS14611. PMID: 25552283.

De Witt Hamer PC, Robles SG, Zwinderman AH, Duffau H, Berger MS. Impact of intraoperative stimulation brain mapping on glioma surgery outcome: a meta-analysis. J Clin Oncol. 2012;30:2559–2565. doi: 10.1200/JCO.2011.38.4818.

Gerritsen JKW, Arends L, Klimek M, Dirven CMF, Vincent AJE. Impact of intraoperative stimulation mapping on high-grade glioma surgery outcome: a meta-analysis. Acta Neurochir (Wien). 2019 Jan;161(1):99-107. doi: 10.1007/s00701-018-3732-4. Epub 2018 Nov 21. PMID: 30465276; PMCID: PMC6331492.

van Lieshout J, Debaene W, Rapp M, Noordmans HJ, Rutten GJ. fMRI Resting-State Connectivity between Language and Nonlanguage Areas as Defined by Intraoperative Electrocortical Stimulation in Low-Grade Glioma Patients. J Neurol Surg A Cent Eur Neurosurg. 2021 Feb 22. doi: 10.1055/s-0040-1721757. Epub ahead of print. PMID: 33618418.

Transcranial direct current stimulation for progressive supranuclear palsy

Transcranial direct current stimulation for progressive supranuclear palsy

Case series

Alexoudi et al. conducted a pilot study in order to evaluate the effect of transcranial direct current stimulation over the motor cortex and premotor cortex in patients with progressive supranuclear palsy, with a particular emphasis on cognitive dysfunction. Eight patients affected by PSP were included (4 males and 4 females with mean age 67.4±7.4 years, range: 55-80 years and mean disease duration: 4.6±3.3 years, range: 1-11 years). The mean Unified Parkinson’s Disease Rating Scale Part III (UPDRS III) was 49±16.1 and the mean Hoehn & Yahr (H&Y) scale was 3.9±1 at baseline. All pharmacological treatments (L-dopa, pramipexole, rotigotine, rasagiline, amantadine) were maintained stable during the study. They aimed at evaluating along with the motor outcome (as it is reflected on a disease-specific rating scale), the post-tDCS cognitive status after the completion of the intervention. The clinical evaluation involved the PSP-Rating Scale, the UPDRS III, and the Timed Up and Go test. The neuropsychological assessment focused on auditory-verbal memory and learning, episodic memory, visuomotor coordination and speed of information processing, executive functions and verbal fluency (phonemic and semantic). Anodal tDCS was applied over primary motor and pre-motor cortices in 10 daily sessions. During the tDCS stimulation, a constant current of 2 mA was delivered for 30 minutes. Clinical evaluations were performed at baseline, day 11, day 30 and at day 90. The PSP-Rating score (total and sections I & III) improved significantly on day 11 compared to baseline and similarly on day 30. A positive effect was also seen in action tremor. In addition to the global mental status improvement, patients showed increases in neuropsychological performance in the domains of visuomotor coordination and processing speed, auditory-verbal learning, episodic memory, phonological and semantic fluency (access and retrieval from lexical memory, selective inhibition, and lexical access speed). The results suggest that tDCS has a beneficial effect on Progressive Supranuclear Palsy patients’ bulbar and motor symptoms, cognitive dysfunction, as well as daily activities, which lasts beyond the duration of the treatment 1).

sham-controlled double-blind crossover design to assess the efficiency of tDCS over the DLPFC in a cohort of 12 patients with PSP. In 3 separate sessions, we evaluated the ability to boost the left DLPFC via left-anodal (excitatory) and right-cathodal (inhibitory) tDCS, while comparing them to sham tDCS. Tasks assessing lexical access (letter fluency task) and semantic access (category judgment task) were applied immediately before and after the tDCS sessions to provide a marker of potential language modulation.

The comparison with healthy controls showed that patients with PSP were impaired on both tasks at baseline. Contrasting poststimulation vs prestimulation performance across tDCS conditions revealed language improvement in the category judgment task following right-cathodal tDCS, and in the letter fluency task following left-anodal tDCS. A computational finite element model of current distribution corroborated the intended effect of left-anodal and right-cathodal tDCS on the targeted DLPFC.

The results demonstrate tDCS-driven language improvement in PSP. They provide proof-of-concept for the use of tDCS in PSP and set the stage for future multiday stimulation regimens, which might lead to longer-lasting therapeutic effects promoted by neuroplasticity.

This study provides Class III evidence that for patients with PSP, tDCS over the DLPFC improves performance in some language tasks 2).

Case reports

Madden et al. report the case of KN, who presented with reduced verbal fluency and connected speech production in the context of PSP. KN completed a set of language tasks, followed by an alternate version of the tasks in conjunction with either sham or active tDCS over the left dorsolateral prefrontal cortex (DLPFC) across four sessions. Results showed improved performance with active stimulation compared to sham stimulation for phonemic fluency and action naming, as well as mixed results suggesting possible benefits for connected speech production. There were no benefits of active stimulation for control tasks, indicating that tDCS can produce specific benefits for phonemic fluency, action naming, and connected speech production in PSP. These promising, preliminary findings warrant further investigation into whether these benefits of tDCS can be a useful therapeutic tool for PSP patients to maintain language 3).



Alexoudi A, Patrikelis P, Deftereos S, Fasilis T, Karakalos D, Verentzioti A, Korfias S, Sakas D, Gatzonis S. Effects of anodal transcranial direct current stimulation on cognitive dysfunction in patients with progressive supranuclear palsy. Psychiatriki. 2019 Oct-Dec;30(4):320-328. doi: 10.22365/jpsych.2019.304.320. PubMed PMID: 32283535.

Valero-Cabré A, Sanches C, Godard J, Fracchia O, Dubois B, Levy R, Truong DQ, Bikson M, Teichmann M. Language boosting by transcranial stimulation in progressive supranuclear palsy. Neurology. 2019 Aug 6;93(6):e537-e547. doi: 10.1212/WNL.0000000000007893. Epub 2019 Jul 3. PubMed PMID: 31270217; PubMed Central PMCID: PMC6709997.

Madden DL, Sale MV, O’Sullivan J, Robinson GA. Improved language production with transcranial direct current stimulation in progressive supranuclear palsy. Neuropsychologia. 2019 Apr;127:148-157. doi: 10.1016/j.neuropsychologia.2019.02.022. Epub 2019 Mar 2. PubMed PMID: 30836131.
WhatsApp WhatsApp us
%d bloggers like this: