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Epilepsy
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Donald C. Barr, Andres M. Kanner
Subdural electrodes are placed directly on the brain as grids or strips (Figure 5.9). These allow for great coverage of the cortical surface and are useful in cortical mapping of eloquent cortex in order to localize sensory, motor, and/or language cortex when the proposed epileptogenic zone being considered is in close approximation. When implanted in large arrangements, subdural electrodes can also assist in determining the extent of the epileptogenic zone to guide surgical resection (Figures 5.10 and 5.11).
Direct cortical electrical stimulation in the treatment of epilepsy
Published in Hans O Lüders, Deep Brain Stimulation and Epilepsy, 2020
Dileep R Nair, Riki Matsumoto, Hans O Lüders, Richard Burgess, William Bingaman
Direct cortical (DC) electrical stimulation has come into routine use as a standard clinical method of evaluating and localizing regions of eloquent cortex. This is done as a part of the invasive pre-surgical evaluation for epilepsy surgery.11–16 There is a subgroup of patients with intractable epilepsies who require an invasive evaluation with the implantation of either subdural grid electrodes or depth electrodes to further localize either the region of seizure onset, eloquent regions of the cerebral cortex, or both. These recordings often take several days to complete.17 Cortical stimulation studies are typically done in the later part of the evaluation for functional localization of language, motor, and sensory regions of the cortex.18
Neurosurgery: Supratentorial tumors
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Essentials of Geriatric Neuroanesthesia, 2019
Monica S. Tandon, Kashmiri Doley, Daljit Singh
Eloquent cortex primarily refers to the main areas involved in speech (Broca's and Wernicke's areas) and sensorimotor functions (primary motor cortex, primary somatosensory cortex) along with the underlying important WM tracts (corticospinal tracts, superior longitudinal fasciculus, arcuate fasciculus); primary visual cortex is also considered as an eloquent area. Resection of tumors that involve or are in close proximity to these regions is associated with a high risk of postoperative motor weakness and language dysfunction.
Electric source imaging for presurgical epilepsy evaluation: current status and future prospects
Published in Expert Review of Medical Devices, 2020
Pierre Mégevand, Margitta Seeck
The accuracy of ESI in localizing epilepsy-related EEG activity has been established by comparing it with the gold standards of intracranial EEG and surgical outcomes [23,29]. This work has increased the confidence of the clinical community in using ESI to localize cerebral activity, and this confidence also extends to other settings where these gold standards are not available [18]. ESI can also contribute to mapping so-called eloquent cortex, the cortical areas that are involved in critical functions like motor control or speech perception and production and should be spared by the surgeon. ESI of somatosensory-evoked potentials recorded with hdEEG accurately localizes sensorimotor cortex around the central sulcus [68]. More recently, ESI and MSI have been applied successfully to identify which cerebral hemisphere is dominant for language [69,70]. Studies on the accurate localization of cortical regions indispensable for speech or memory with hdEEG are still pending, but the situation is likely to evolve favorably with refinements in data analysis and knowledge of the size and number of modules of the underlying networks.
Beyond descriptive neurology: Broca, cerebral hemodynamics, and cortical function
Published in Journal of the History of the Neurosciences, 2018
Perhaps the most interesting aspects of Broca’s work to the modern neuroscientist was his attempts to record the effects of cerebral activity during the performance of intellectual tasks, such as reading aloud and doing complicated arithmetic. Under normal conditions, there is a close coupling between cerebral metabolism and CBF, such that if metabolic activity increases in response to the performance of a task, the blood supply to the region involved also increases to meet metabolic demands. Positron emission tomography and magnetic resonance imaging (MRI) make it possible to assess CBF in awake and responsive individuals. The procedure is referred to as functional activation or functional imaging (see Fig. 1). Functional imaging is performed today as Broca originally conceived of it: an individual performs a predetermined task while he or she is in the PET or MRI scanner. The task can be motor, sensory, or cognitive. Cerebral metabolic activity increases in the area responsible for performing the task, which is identified by visualizing the concomitantly increased CBF on an arbitrary color scale. Functional imaging, using MRI, is now available in many centers to determine the proximity of a structural brain lesion to eloquent cortex prior to surgery (Leblanc et al., 1992). It has also become a most useful tool in neuropsychological research in normal volunteers (Klein et al., 1995).
Awake craniotomy for assisting placement of auditory brainstem implant in NF2 patients
Published in Acta Oto-Laryngologica, 2018
Qiangyi Zhou, Zhijun Yang, Zhenmin Wang, Bo Wang, Xingchao Wang, Chi Zhao, Shun Zhang, Tao Wu, Peng Li, Shiwei Li, Fu Zhao, Pinan Liu
Awake craniotomy is a preferred approach in the resection of brain lesions in the eloquent cortex, which provides a unique opportunity for mapping sensorimotor, language, and cognitive functions, allowing the operator to optimize the extent of resection while preserving the patient’s quality of life [15,16]. Regarding ABI surgery, we suppose that intraoperative cochlear nucleus mapping in awake craniotomy may assist the placement of the electrode array accurately. By stimulating the cochlear nucleus in awake patients, we can adjust the electrode array position to obtain more active electrodes. In addition, threshold levels and distinct pitches, which are thought to be related to high levels of speech recognition, may be achieved in the wake-up hearing test [6,7].