Brain mapping in tumors: Intraoperative or extraoperative?

Abstract

SUMMARYIn nontumoral epilepsy surgery, the main goal for all preoperative investigation is to first determine the epileptogenic zone, and then to analyze its relation to eloquent cortex, in order to control seizures while avoiding adverse postoperative neurologic outcome. To this end, in addition to neuropsychological assessment, functional neuroimaging and scalp electroencephalography, extraoperative recording, and electrical mapping, especially using subdural strip-or grid-electrodes, has been reported extensively. Nonetheless, in tumoral epilepsy surgery, the rationale is different. Indeed, the first aim is rather to maximize the extent of tumor resection while minimizing postsurgical morbidity, in order to increase the median survival as well as to preserve quality of life. As a consequence, as frequently seen in infiltrating tumors such as gliomas, where these lesions not only grow but also migrate along white matter tracts, the resection should be performed according to functional boundaries both at cortical and subcortical levels. With this in mind, extraoperative mapping by strips/grids is often not sufficient in tumoral surgery, since in essence, it allows study of the cortex but cannot map subcortical pathways. Therefore, intraoperative electrostimulation mapping, especially in awake patients, is more appropriate in tumor surgery, because this technique allows real-time detection of areas crucial for cerebral functions-eloquent cortex and fibers -throughout the resection. In summary, rather than choosing one or the other of different mapping techniques, methodology should be adapted to each pathology, that is, extraoperative mapping in nontumoral epilepsy surgery and intraoperative mapping in tumoral surgery.

Epilepsy and brain tumors

“…The majority of ECoG recordings of tumoral epilepsy are performed intraoperatively interic-tally (Sugano et al, 2007; Duffau, 2013), although some groups have also advocated for extraoperative ictal ECoG with subdural grid and strip electrodes in tumor-related epilepsy surgery (Sweet et al, 2013). While extraoperative ictal recordings are critical in many cases of nonlesional focal epilepsy to localize the epileptogenic zone de novo , the site of seizure onset in tumor-associated epilepsy is presumed a priori to be in the peritumoral region.…”

The roles of blood-derived macrophages and resident microglia in the neuroinflammatory response to implanted Intracortical microelectrodes

“…Intracortical microelectrodes can record signals from individual or small populations of neurons within the brain. Recorded signals can then be used as control signals to functionally map neuronal circuits and advance our understanding of normal brain function as well as the progression of several diseased states [3–6]. In addition, recent advances in microelectrode technology have enabled researchers to use recorded signals to control several assist devices for rehabilitation applications [7–11].…”

Glioma localization and excision using direct electrical stimulation for language mapping during awake surgery

“…For low-grade glioma, the tumor may be resected to the maximum extent under the premise of retaining the important brain functions, thus prolonging the survival period. For high-grade glioma, cortical DES avoids surgery-induced functional deficits, and improve the patients' survival qualities (30)(31)(32)(33). De Witt Hamer et al (9) completed a meta-analysis, which collected 90 documents and the surgical situations of 8,091 glioma cases, and found that the rate of long-term severe neurological dysfunction subsequent to DES was 3.4%, while the long-term severe disability rate of patients that underwent surgery without DES was 8.2%.…”