2021 Volume 30 Issue 7 Pages 496-503
Since better outcomes for mesial temporal lobe epilepsy (MTLE) was reported in 2001, epilepsy surgeries have been established as a treatment for medically intractable epilepsy. Among them, five types of epilepsy surgery (amygdalohippocampectomy for MTLE, lesionectomy for focal epilepsy with or without apparent MRI lesions, hemispherotomy for hemispheric epilepsy, and callosotomy for drop attacks) are known as surgically remediable epileptic syndromes. Furthermore, in 2010, vagal nerve stimulation was approved as a palliative surgery for epilepsy in Japan.
When the epileptogenic focus is undetermined in non-invasive evaluations such as scalp electroencephalography (EEG), MRI, and positron emission tomography, invasive evaluation using intracranial electrodes might be performed subsequently. Conventionally, subdural grid EEG was mainly used for detecting the epileptogenic focus ; however, the percentage of the use of depth electrodes with the stereotactic method of EEG implantation (SEEG) has been increasing recently. SEEG is supposed to be insufficient in terms of confirming cortical seizure propagation and performing functional mapping with electrical stimulation, but it has been widely adopted because of its low invasiveness. When planning the location of the electrodes, a hypothesis of the seizure focus and its propagation needs to be set up based on the anatomo-clinico-electrical correlation.
When the epileptogenic focus is in a limited area of the brain, less invasive approaches should be selected for the removal of the lesion. On the other hand, when the epileptic network affects a wide part of the brain, surgeries based on the disconnection concept, such as corpus callosotomy, multi-lobe disconnection, and hemispherotomy, should be considered.
Although unapproved in Japan, new concepts of surgery, such as focus coagulation, deep brain stimulation, and responsive neurostimulation, have become popular instead of focus resection, especially in cases of epilepsy originating from eloquent areas. Here, we describe the concept of epilepsy surgery and the current topics in this field.
