Glossary of Epilepsy Terms
Responsive neurostimulation device: RNS consists of a small neurostimulator implanted within the skull under the scalp. The neurostimulator is connected to one or two wires (called electrodes) that are placed where the seizures are suspected to originate within the brain or on the surface of the brain. The device detects abnormal electrical activity in the area and delivers electrical stimulation to normalize brain activity before seizure symptoms begin.
Seizure: an event of altered brain function caused by abnormal or excessive electrical discharges in the brain. Most seizures cause sudden changes in behavior or motor function.
Seizure focus: the area of the brain in which a seizure starts.
Status epilepticus: a prolonged seizure (usually defined as lasting longer than 30 minutes) or a series of repeated seizures without regaining consciousness. Status epilepticus is a medical emergency and medical help should be obtained immediately.
Temporal lobe resection: a surgical procedure in which brain tissue in the temporal lobe is cut away (resected) to remove the seizure focus.
Tonic seizure: a seizure that is characterized by stiffening of the muscles, sustained for more than a few seconds.
Tonic-clonic seizure: a seizure marked by loss of consciousness, falling, stiffening, and jerking. This is the hallmark of a generalized motor seizure, which used to be called a "grand mal seizure."
Vagus nerve: a small cranial nerve that passes through the neck and is connected to various areas of the brain and other organs in the body, including the stomach, heart, and lungs.
Vagus nerve stimulation: a surgical treatment for epilepsy involving implantation in the neck of an electrode on the vagus nerve. The electrode is connected to a pacemaker that is placed under the skin in the chest. While the VNS is usually programmed to cycle continuously, the patient can turn the stimulator on, using a small magnet placed over the pacemaker, if he or she feels a seizure coming on.