Epilepsy is a neurological disorder characterized by recurrent, unprovoked seizures. While medication successfully controls seizures for about two-thirds of patients, roughly 30% develop drug-resistant epilepsy, also called refractory epilepsy. This means their seizures continue despite adequate trials of two or more appropriate anti-seizure medications. For this specific patient population, surgery may offer the possibility of achieving seizure freedom. For carefully selected patients, surgery can lead to a long-term absence of disabling seizures, which is the functional equivalent of a cure.
Identifying Candidates for Curative Surgery
The success of epilepsy surgery depends on identifying the precise location where seizures originate, known as the epileptogenic zone. Only patients with focal epilepsy—seizures starting in one specific, removable area—are considered candidates for a curative procedure. The evaluation is a multidisciplinary effort, often involving neurologists, neurosurgeons, and neuropsychologists, ensuring a comprehensive view of the patient’s condition.
The process begins with non-invasive tests. High-resolution Magnetic Resonance Imaging (MRI) detects structural abnormalities like tumors or scar tissue that might be causing the seizures. Video-Electroencephalography (Video-EEG) monitoring is mandatory, recording brain waves and physical symptoms during seizure events to pinpoint the seizure onset zone.
Specialized non-invasive scans like Positron Emission Tomography (PET) or Single-Photon Emission Computed Tomography (SPECT) may identify areas of abnormal metabolism or blood flow. Neuropsychological testing assesses memory, language, and cognitive functions to predict the functional risk of removing the identified area. If non-invasive tests fail to provide clear localization or if the focus is near a functionally important region, an invasive phase may be required, involving the surgical placement of electrodes directly on or into the brain.
Resective and Minimally Invasive Surgical Approaches
The goal of curative epilepsy surgery is to remove or destroy the epileptogenic zone. The oldest and most established method is resective surgery, which involves opening the skull in a procedure called a craniotomy and surgically removing the identified brain tissue. This approach includes temporal lobectomy, often used for mesial temporal lobe epilepsy, and lesionectomy.
Anterior temporal lobectomy, which removes the front part of the temporal lobe, amygdala, and hippocampus, is a common and successful resective procedure for drug-resistant epilepsy. Lesionectomy is performed when the seizure focus is a well-defined structural lesion, often resulting in high success rates. These procedures are considered the gold standard but carry the risks associated with open brain surgery and require a longer recovery time.
A newer, less invasive alternative is Laser Interstitial Thermal Therapy (LITT). LITT uses MRI guidance to insert a thin fiber through a small skull opening, delivering heat to destroy the seizure-generating tissue through thermal ablation. LITT offers a quicker recovery and fewer general surgical complications than traditional open surgery. Although resective surgery currently has a slightly higher seizure freedom rate, LITT is increasingly used for deep-seated or small lesions due to its minimally invasive nature.
Measuring Surgical Success and the Concept of “Cure”
A “cure” in epilepsy is defined as achieving long-term seizure freedom, often allowing for the reduction or elimination of anti-seizure medications. The standard tool for measuring surgical outcome is the Engel classification scale. The highest measure of success is an Engel Class I outcome, meaning the patient is completely free of disabling seizures or experiences only non-disabling auras.
The likelihood of achieving this outcome varies based on the epilepsy type and procedure. For patients with mesial temporal lobe epilepsy, success rates for seizure freedom (Engel Class I) are estimated to be between 60% and 70% after resective surgery. For extra-temporal lobe resections, the success rate is generally lower, ranging from 40% to 50%.
Long-term follow-up studies show that while seizure freedom rates decrease slightly over time, the benefit remains substantial. For example, the probability of remaining seizure-free is around 67% at five years and 51% at ten years post-surgery. Achieving seizure freedom significantly improves quality of life and reduces the risk of sudden unexpected death in epilepsy (SUDEP). Even without complete seizure freedom, a significant reduction in frequency is considered a worthwhile improvement.
Potential Risks and Long-Term Considerations
Epilepsy surgery carries general risks such as bleeding, infection, and complications related to anesthesia. Beyond these, there are specific risks of functional deficits directly related to the area of the brain that is removed or ablated. The most common functional risk, particularly in temporal lobe surgery, is memory decline, especially when the surgery is performed on the dominant hemisphere for language.
Language difficulties, visual field deficits, and weakness can occur depending on the epileptogenic zone’s proximity to areas controlling speech, vision, or movement. The presurgical evaluation, including neuropsychological testing and functional MRI, is designed to anticipate these risks and weigh them against the benefit of seizure freedom. While many functional changes after surgery are temporary, some deficits, such as a partial loss of vision in one field, can be permanent.
Long-term monitoring is necessary even after successful surgery, as seizures can return years later. For example, about one-third of patients who are initially seizure-free may experience a recurrence within five years. The possibility of recurrence necessitates ongoing communication with the patient’s epilepsy care team, even if medications are eventually discontinued under medical supervision. The long-term benefit of successful surgery is often a significant improvement in overall quality of life and a reduced need for medication, but it is not a guarantee against future seizures.