Currently, epilepsy surgery is mainly used for refractory epilepsy and secondary epilepsy.
The diagnostic criteria for refractory epilepsy are
( 1 ) The duration of epilepsy is more than 3 to 4 years.
( 2 ) At least 1 seizure per month.
( 3 ) The seizures cannot be controlled by long-term, systematic treatment with multiple antiepileptic drugs, even with blood drug concentration monitoring.
( 4 ) Those who are severely disabled due to frequent seizures, which affect work, study and life.
The clinical understanding of identifying refractory epilepsy conditions is not consistent, with some overemphasizing the number of seizures per month while ignoring the serious impact of seizures on the patient’s life and learning. Some believe that an average of more than one seizure per month (e.g., complex partial seizures or secondary generalized seizures) is sufficient to affect the patient’s normal life and learning, and surgical treatment can be considered.
Refractory epilepsy is the main indication for epilepsy surgery, taking into account the patient’s age, intellectual development, secondary epilepsy, and the presence of systemic disease. Regarding the age of the patient for surgery, most advocate early surgery. Surgery after the age of 50 is less effective because of degenerative brain degeneration, even if epilepsy no longer occurs.
For patients with an IQ below 70, surgery has been considered inappropriate in the past. In recent years, clinical practice has shown that some of these patients have significantly improved seizures after surgery, the dosage of antiepileptic drugs has been reduced, and their intelligence has improved significantly. For example, a 13-year-old girl with severe seizures and high dosage of medication had very poor intelligence and had to attend a school for the mentally retarded, but after surgery the seizures disappeared and her intelligence improved significantly six months later.
In secondary epilepsy, simple removal of the lesion can usually control the seizures and reduce the dosage of antiepileptic drugs, so for secondary epilepsy, early surgical treatment is best if the lesion is found.
The preoperative evaluation and localization of the epileptic foci is very important in epilepsy surgery (the most important factor in determining the success of the surgery). In recent years, the clinical application of neuroimaging (CT, MRI, DSA), neurophysiology (EEG, SEEG, ECOG, AEEG), neuro-nuclear medicine (SPECT, PET), magnetoencephalography (MEG) and functional MRI has effectively improved the preoperative localization of epileptogenic foci and greatly promoted the development of epilepsy surgery.
Epilepsy surgery modalities mainly include: temporal lobectomy, anteromedial temporal lobectomy, selective amygdala-hippocampal resection, cerebral cortical resection, corpus callosotomy, cerebral hemisphere resection, cortical thermal cautery, multiple submural transverse fiber dissection, stereotactic disruption, vagus nerve stimulation, thalamic stimulation and cerebellar stimulation.
(i) Surgical treatment of temporal lobe epilepsy
Temporal lobe epilepsy, also known as psychomotor epilepsy, is an epilepsy with simple partial seizures, complex partial seizures or secondary generalized seizures originating from the temporal lobe, accounting for about 1/4 to 1/3 of all epilepsy. Currently, temporal lobe epilepsy is the type of epilepsy with the best surgical outcome. Surgical options include temporal lobectomy, anteromedial temporal lobectomy, selective amygdala-hippocampal resection, and navigated temporal lobe lesion resection. Temporal lobectomy and anteromedial temporal lobectomy are most often performed in the lateral type of temporal lobe epilepsy, and selective hippocampal-amygdala resection in the medial type.
Indications for surgery.
( 1 ) Preoperative EEG or 24-hour EEG monitoring indicates that the epileptogenic focus is located in one temporal lobe.
( 2) Preoperative CT, MRI, SPECT, PET, etc. confirm the presence of obvious epileptogenic foci in one temporal lobe or medial temporal lobe.
( 3 ) Clinical manifestation of complex partial seizures with typical aura before the seizure, such as rising sensation of abdominal gas, phantom smell, phantom taste, etc., accompanied by limited twitching of the contralateral limb or face.
( 4 ) Patients with organic lesions in the temporal lobe region that may cause seizures.
(ii) Corticotomy
Corticotomy is one of the most basic and oldest surgical methods for the treatment of limited epilepsy. With the continuous improvement of surgical techniques, it has become one of the most important surgical procedures for the treatment of epileptogenic foci located in non-functional areas of the cerebral hemispheres. With the development of modern medical imaging, the localization of cortical epileptogenic foci has become more precise and the success rate of this procedure has become higher.
Indications for surgery.
( 1 ) Patients with intractable epilepsy, who still have intermittent seizures while taking medication, and the epileptogenic focus is found to be located in the resectable cortical area of the cerebral hemisphere by EEG and MRI.
( 2 ) Patients with limited epilepsy due to various causes, and the epileptogenic focus is located within the non-functional cortical area of the cerebral hemisphere.
( 3 ) After comprehensive preoperative evaluation, it is considered that no serious neurological dysfunction will be caused after surgery.
(3) Corpus callosum dissection
1.Anterior corpus callosotomy
Indications for surgery.
( 1 ) Refractory epilepsy with a clear diagnosis and a predominance of atonic, tonic and/or tonic-clonic seizures.
( 2 ) Multifocal or widespread epilepsy with an unclear location of the primary epileptogenic focus, located in one or both hemispheres of the brain, where other surgical methods cannot relieve the seizures.
( 3 ) Diffuse and widespread epileptogenic foci with secondary generalized changes on the EEG. These include Rasmussen syndrome, Lennox-Gasstaut syndrome, infantile hemiparesis, and Sturge-Weber syndrome.
( 4 ) Age, mental retardation, and EEG findings are not limited.
2, Posterior corpus callosotomy
3 Indications for surgery Same as anterior corpus callosotomy
The excellent rate of seizure control with corpus callosotomy is high.
(iv) Cerebral hemispherectomy
1. Anatomical cerebral hemispherectomy
Indications for surgery.
( 1 ) Infants with hemiplegia with intractable epilepsy.
( 2 ) The presence of extensive multifocal epileptogenic foci in one hemisphere (e.g., lesions caused by perinatal diseases, traumatic brain injury, cerebrovascular diseases, etc.), which have caused severe dysfunction of the contralateral limb, including motor, sensory, language, etc.
( 3 ) The presence of an underlying disease with progressive deterioration in one cerebral hemisphere that causes epileptic seizures. For example, Sturge-Weber syndrome, chronic cerebritis, etc.
2.Functional hemispherectomy
This method is a modified version of hemispherectomy, which was created by Rasmussen. It allows the diseased hemisphere to completely lose contact with the contralateral hemisphere in terms of cortical function. The volume of the postoperative residual cavity is reduced to minimize complications SCH
etc. occur. The excellent efficiency of this procedure is high.
(v) Multiple subchoroidal transverse fiberotomy (MST)
MST for the treatment of limited epilepsy mainly refers to epileptic foci located in major functional areas of the brain. These functional areas include speech, sensory, and motor areas, and if the epileptogenic focus in this area is removed using the previous surgical approach, postoperative dysfunction in this area will be left behind. With the MST approach, the epileptogenic foci are cut into multiple vertical slices, resulting in a loss of intracortical contact, which not only controls the seizures but also preserves the corresponding function of the area.
Indications for surgery.
( 1 ) In intractable epilepsy, the epileptogenic foci are mainly confined to the major functional areas of the brain, including the precentral gyrus, posterior gyrus, Broca’s area, Wenricks’ area, angular gyrus, and supramarginal gyrus of the dominant hemisphere; or the epileptogenic foci are accumulated in multiple functional areas.
( 2 ) Persistent epileptiform discharges in the main functional areas of the brain after resection of epileptogenic foci in non-major cortical areas.
( 3 ) Partial seizure continuity – motor or sensory.
( 4 ) Patients with Rasmusen’s encephalitis in which the epileptic focus is located in the motor area (those not suitable for hemispherectomy).
( 5 ) Alternative to hemispheric cortical resection for infantile hemiplegia with seizures.
( 6 ) Landau-kleffner syndrome.
MST has a high efficiency in the treatment of epilepsy.
(6) Cortical thermal cautery
Thermal cautery of epileptogenic areas of the cerebral cortex using low-power bipolar electrocoagulation can denature transverse fibers in multiple superficial cortical areas, thus blocking the synchronized spread and propagation of epileptic discharges in horizontal direction and suppressing seizures, while normal functions of the cerebral cortex are not affected. It is particularly suitable for the surgical treatment of functional area epilepsy and generalized seizure epilepsy with extensive cortical discharges. This method is safe and reliable, with high efficiency, and is one of the more clinically used methods at present.
(VII) Stereotactic disruption
Indications for surgery.
( 1 ) Patients with various seizure types of intractable epilepsy who cannot choose surgical resection treatment.
( 2 ) Patients with epileptogenic foci confined to one hemisphere and without obvious focal organic lesions.
( 3 ) Preoperative examination reveals that the epileptogenic focus is located deep in the brain or around important brain structures.
Currently, the common targets are the amygdala and Forel-H area.
(viii) Vagus nerve stimulation (VNS)
In 30% to 40% of patients with epilepsy, antiepileptic drugs are ineffective and the site of seizure is unclear, making it difficult to perform surgery. Intermittent left-sided vagus nerve stimulation can control intractable seizures or significantly reduce the number of seizures. Since 1988, more than 6000 patients with refractory epilepsy have been treated with VNS worldwide.
Indications.
( 1 ) Partial, especially complex partial seizures, or generalized seizures secondary to complex partial seizures.
( 2 ) Seizure frequency, average of more than 6 seizures per month, or a maximum interval of less than 14 days between seizures over a two-year period.
( 3 ) Age 16 to 60 years, good intelligence, IQ value greater than 80.
( 4 ) No history of psychiatric disorders or asthma, cardiopulmonary disorders or other progressive systemic diseases.
( 5 ) Preoperative phenytoin sodium or carbamazepine or a combination of both for at least 1 month and proven ineffective.
Contraindications.
( 1 ) Peptic ulcer.
( 2 ) Cardiac arrhythmia.
( 3 ) Progressive neurological disease.
( 4 ) Pregnancy.
( 5 ) Poor general condition.
( 6 ) Age under 12 years or over 60 years.
( 7 ) Skin infection foci on the left side of the neck and chest.
(ix) Chronic thalamic stimulation
Indications.
( 1 ) Meet the diagnostic criteria for refractory epilepsy, with two years of ineffective or poor efficacy of regular drug therapy, and still have frequent seizures > 4 times per month.
( 2 ) Primary epilepsy, drug therapy is ineffective.
( 3 ) EEG tracing indicates diffuse brain wave abnormalities, or the abnormal brain waves originate bilaterally, rather than being confined to a small area.
( 4 ) MRI, CT examination to exclude intracranial occupying lesions.
( 5 ) IQ should be greater than 70.
( 6 ) This method should be used with caution in infants and older people.
Contraindications.
( 1 ) Elderly and frail patients who cannot tolerate anesthesia and surgery, or those with severe heart, lung, liver and kidney dysfunction.
( 2 ) Recurrent seizures have affected the intellectual development (IQ less than 70) or have psychiatric abnormalities.
( 3 ) Those with intracranial occupying lesions or localized brain dysplasia.
( 4 ) Severe cerebral atrophy, ventricular enlargement or cerebral penetration malformation.
( 5 ) Those who have broken or infected scalp or subclavian skin.
Chronic thalamic stimulation is safe and effective, but the number of accumulated cases is relatively small and needs further observation.
(x) Chronic cerebellar stimulation
Indications.
( 1 ) Chronic cerebellar stimulation can be used in refractory epilepsy that has failed to respond to two years of regular drug therapy or has poor efficacy if no occupying lesions are found on imaging.
( 2 ) Refractory epilepsy originating from a bilateral or extra-temporal lobe epileptic focus.
( 3 ) IQ (intelligence quotient) should be at least 70.
( 4 ) Age should be less than 60 years and should be used with caution in children.
Contraindication signs.
( 1 ) Patients of advanced age or frail patients who cannot tolerate anesthesia and surgery.
( 2 ) Infection of the head or subclavian local skin.
( 3 ) Those with occupying lesions or progressive neurological disease detected by imaging.
( 4 ) Those with IQ below 70 or who cannot cooperate with extracorporeal stimulation after surgery.
Editor’s Tip.
Epilepsy treatment is a systemic project that requires the collaboration of neurology, neurosurgery, neuropsychology, psychiatry, electrophysiology and imaging specialists to best treat a patient with epilepsy. Performing surgery before a definitive characterization and localization is obtained is irresponsible to the patient.