Intraoperative electrical stimulation in awake craniotomy: methodological aspects of current practice

Abstract

<jats:p>There is increasing evidence that the extent of tumor removal in low-grade glioma surgery is related to patient survival time. Thus, the goal of resecting the largest amount of tumor possible without leading to permanent neurological sequelae is a challenge for the neurosurgeon. Electrical stimulation of the brain to detect cortical and axonal areas involved in motor, language, and cognitive function and located within the tumor or along its boundaries has become an essential tool in combination with awake craniotomy. Based on a literature review, discussions within the European Low-Grade Glioma Group, and illustrative clinical experience, the authors of this paper provide an overview for neurosurgeons, neurophysiologists, linguists, and anesthesiologists as well as those new to the field about the stimulation techniques currently being used for mapping sensorimotor, language, and cognitive function in awake surgery for low-grade glioma. The paper is intended to help the understanding of these techniques and facilitate a comparison of results between users.</jats:p>

Combined noninvasive language mapping by navigated transcranial magnetic stimulation and functional MRI and its comparison with direct cortical stimulation

“…16,23,41,51,54 Another difference may be the impact of rTMS on functional connectivity, since rTMS may affect subcortical pathways more significantly than bipolar DCS. 17,25,41,64,73 This may be a reason for rTMS producing more false-positive results than DCS. On the other hand, the subcortical affection by rTMS may be an approach toward the mapping of language-positive sites in the future.…”

“…1,41,47,57,70 Of course, compliance always plays an important role in the analysis of hu-man brain function, especially regarding the detection of language-eloquent regions by DCS. 73 But the examiners cannot control compliance during the object-naming task in the MR scanner. In contrast, a lack of cooperation is immediately noticeable during the rTMS language mapping.…”

Functional MRI, Diffusion Tensor Imaging, Magnetic Source Imaging and Intraoperative Neuromonitoring Guided Brain Tumor Resection in Awake and Under General Anaesthesia

“…The elements to this include the stimulator device, the stimulation parameters consisting of pulse type, pulse width (pulse interval), frequency of stimulation, intensity of the stimulation and the stimulation probe. The followings are key points mentioned by Szelenyi et al that any neurosurgeon who practices direct cortical electrical stimulation need to be familiar with [4]:…”

“…Neuronal property of creating oscillation inside our brain is important for normal brain functioning. Neural oscillation contributes to neural coding, brain rhythms with different types or frequency of oscillatory activity [5 type of brain waves: gamma (above 30 Hz), beta [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], alpha (8)(9)(10)(11)(12)(13), theta [4][5][6][7][8] and delta [0.5 -4 Hz); sleep spindles; Mu waves; thalamocortical oscillations; epileptic seizures and bursting] and fast information processing and transfer. Interestingly, neural oscillations also play an important role in many neurological disorders such as excessive synchronisation during seizure in epilepsy or tremors in movement disorders [69].…”

“…Safer and successful brain tumors surgery requires not only neuroimages-guided surgery but also properly defined the eloquent (important and functional) cortices and monitoring of the vital areas of the brain and other organs. Awake surgery with intraoperative brain mapping, and surgery under general anaesthesia with intraoperative monitoring (IOM) which are guided by neuroimages are two operative techniques for brain tumors that are currently regarded by most as gold standard [4][5][6][7][8]. This chapter describes the current functional neuroimaging modalities (fMRI, DTI and MSI), brain mapping, surgery under awake and unconscious states with intraoperative neuromonitorings as adjuncts and techniques to plan and guide the surgeon to resect the brain tumors successfully.…”