Vagal Nerve Stimulation and Epilepsy :: Biology Essays Research Papers

Vagal Nerve Stimulation and Epilepsy Epilepsy is a brain disorder characterized by seizures which occur when neurons fire uncontrollably and chaotically. The four most common categories of seizures are: simple partial, complex partial, secondary generalized tonic-clonic, and generalized tonic-clonic. A partial seizure is one in which epileptic activity stays in a focused area of the brain. During a simple partial seizure, the patient maintains full consciousness and experiences hallucinations, illusions and/or muscle jerking. A patient experiencing a complex partial seizure has impaired consciousness and often makes automated movements. A generalized tonic-clonic (GTC) seizure is characterized by complete loss of consciousness, rhythmic jerking, and a period of unresponsiveness. A secondary generalized tonic-clonic (SGTC) seizure is one in which the epileptic activity of a partial seizure spreads to the entire brain, resulting in a generalized seizure.(3). Epilepsy has a variety of different pathologies. These include genetic factors, poisoning, and brain injury. High levels of excitatory neurotransmitters, low levels of inhibitory neurotransmitters, and abnormal wiring are all thought to be causes of seizures. Possibly, abnormalities in the cell membrane play a part in causing seizures. (3). This makes sense since the cell membrane essentially controls the polarization of the cell, which in turn controls the activation of signaling between cells. Often, seizures are caused by a deficiency of GABA, a neurotransmitter which inhibits the passing of information from one neuron to another. (1). Seizures which are caused by lack of inhibitor could, in a way, be likened to the example of a chicken which runs around for some time after its head is cut off. The spastic wild activity of the chicken is due to the fact that the inhibitory neurons are all in the head, which was removed. There is nothing to control the excitatory neurons. Similarly, without enough inhibiting GABA, many neurons send signals all at once, and there is nothing to stop them. One of the more recent forms of treatment for epilepsy is called Vagal Nerve Stimulation (VNS). The first VNS device was implanted into a human in 1988. ((2).) The vagus nerve is a cranial nerve controlling muscles involved with swallowing, speaking and coughing. The nerve is also involved with receiving input from and sending information about the heart, stomach and lungs to the brain. (6). The Vagus Nerve Stimulator is a small generator which sends electrical activity to the brain to prevent seizures. (5).