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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Epilepsy surgery | 1/2 | https://en.wikipedia.org/wiki/Epilepsy_surgery | reference | science, encyclopedia | 2026-05-05T09:19:31.127122+00:00 | kb-cron |
Epilepsy surgery involves a neurosurgical procedure where an area of the brain involved in seizures is either resected, ablated, disconnected or stimulated. The goal is to eliminate seizures or significantly reduce seizure burden. Approximately 60% of all people with epilepsy (0.4% of the population of industrialized countries) have focal epilepsy syndromes. In 20% to 30% of these patients, the condition is not adequately controlled with adequate trials of two anticonvulsive drugs, termed drug resistant epilepsy, or refractory epilepsy. Such patients are potential candidates for surgical epilepsy treatment. First line therapy for epilepsy involves treatment with anticonvulsive drugs, also called antiepileptic drugs– most patients will respond to trials of one or two different medications. The goal of treatment is the elimination of seizures, since uncontrolled seizures carry significant risks, including injury and sudden unexpected death in epilepsy. In patients with refractory epilepsy, surgery is considered the only curative option. Epilepsy surgery has been performed for more than a century, but its use dramatically increased in the 1980s and 1990s, reflecting advancement in technique and improved efficacy in selected patients.
== Evaluation == The pre-surgical evaluation for epilepsy is designed to locate the "epileptic focus" or the "epileptogenic zone" (the location where the epilepsy originates in the brain) and to determine if/how surgery could affect normal brain function. Defining the epileptogenic zone has a fundamental role in determining the boundaries of the area that needs to be removed in order to relieve seizures but also to avoid harming the "eloquent cortex" or areas of the brain that control functions such as language, motor control, or vision. Resective surgery involves cutting away or disconnecting areas of the brain that are generating or propagating seizures. Epileptologists, neurologists with special training in epilepsy, will also confirm the diagnosis of epilepsy to make sure that seizure-like activity is truly due to epilepsy as opposed to non-epileptic seizures. The evaluation typically includes neurological physical examination, routine electroencephalography (EEG), Long-term video-EEG monitoring, neuropsychological evaluation, and neuroimaging such as MRI, functional magnetic resonance imaging (fMRI), single photon emission computed tomography (SPECT), positron emission tomography (PET), and magnetoencephalography (MEG). Neuroimaging can help identify if there is a structural cause for the seizures, such as a tumor or abnormal blood vessels such as arteriovenous malformations (AVMs). Several imaging techniques including MRI, SPECT, and PET have been found to identify the epileptogenic zone in anywhere from 50% to 80% of cases. Some epilepsy centers use intracarotid sodium amobarbital test (Wada test) and fMRI when evaluating temporal lobe epilepsy surgery, as surgeries in this area of the brain can affect memory. Recent studies note fMRI outperforming the Wada test for memory and language localization. Current research into pre-surgical evaluation includes computer models of seizure generation, high-frequency oscillations as biomarkers of epilepsy, and magnetoencephalography for repeat epilepsy surgeries. If noninvasive testing was inadequate in identifying the epileptic focus or in distinguishing the surgical target from normal brain tissue and function, then long-term video-EEG monitoring with the use of intracranial electrodes may be required for evaluation. Brain mapping by the technique of cortical electrical stimulation or electrocorticography are other procedures used in the process of invasive testing for certain patients. Once the epilepsy focus is located, the specific surgery involved in treatment is decided on. The type of surgery depends on the location of the seizure focal point. Surgeries for epilepsy treatment include, but are not limited to: temporal lobe resection, hemispherectomy, ground temporal and extratemporal resection, parietal resection, occipital resection, frontal resection, extratemporal resection, and callosotomy.
== Hemispherectomy == Hemispherectomy or hemispherotomy involves removal or a functional disconnection of most, or all of, one half of the brain typically leaving the basal ganglia and thalamus. It is reserved for people with the most catastrophic epilepsies, such as those due to Rasmussen's encephalitis. If the surgery is performed on very young patients (2–5 years old), then the remaining hemisphere may acquire some motor control of the ipsilateral body due to neuroplasticity; in older patients, paralysis results on the side of the body opposite to the part of the brain that was removed with less prospect for recovery. A visual field defect is an unavoidable side effect, typically involving a homonymous hemianopia involving loss of the half of the visual field on the same side of the disconnected brain. Because of these and other side-effects, it is usually reserved for patients having exhausted other treatment options, including for children under 3 years of age who have drug-resistant epilepsy. Hemispherectomies can be divided into three main types: anatomic, functional, and hemidecortication. Anatomic hemispherectomy involves the surgical removal of an entire cerebral hemisphere excluding deep structures such as the basal ganglia, thalamus, and brainstem to preserve vital functions. WE Dandy recorded the first anatomic hemispherectomy in 1928 for glioma resection and the first surgery for epilepsy was performed by McKenzie ten years later. This approach is less commonly performed due to high risks of complications, such as hydrocephalus due to blockage of the foramen of Monro, one of the passages that drains cerebrospinal fluid in the brain and spine, and superficial cerebral hemosiderosis (SCH). The procedure became less popular with the introduction of new antiepileptic drugs in the 1960s. Functional hemispherectomies differ in that they disconnect the affected hemisphere from the rest of the brain to prevent spread from the epileptogenic focus to other parts of the brain. Structures involved can include the corpus callosum and thalamocortical fibers, as they are implicated in relaying information between the brain's hemispheres. Many approaches are available and overall are described according to their surgical plane including vertical (between the two hemispheres) and lateral (along the Sylvian fissure). Depending on each patient case, alternate procedures such as hemidecortication or peri-insular hemispherectomies are available to disrupt the epilepsy signal but remain less invasive to minimize risks.