New type of brain mapping

Epilepsy is a condition characterized by periods of disturbance in the electrical activity in the brain. According to the Epilepsy Foundation, more than three million Americans have epilepsy. About 200,000 new cases occur each year. It can develop at any age, but most commonly appears during childhood or old age.There are two main classes of seizures: generalized seizures and partial seizures. Generalized seizures affect both sides of the brain from the onset.

They can be further classified into several categories. Myoclonic seizures are characterized by rapid twitches of the muscles in the upper body, arms or legs. They usually affect both sides of the body at the same time. Atonic seizures (sometimes referred to as “drop attacks”) cause a loss of muscle tone, leading the head to drop or the person to suddenly fall down. Absence seizures (also referred to as petite mal seizures) cause a sudden lapse of awareness. These seizures are usually brief and may be described as “staring into space.”

General tonic clonic seizures (grand mal seizures) are the most common type of generalized seizure. They start with stiffening of the limbs and then jerking of the face, arms and/or legs. Patients usually lose consciousness.Partial seizures (also called focal seizures) occur in one specific area of the brain. These types of seizures are more common than generalized seizures. In a simple partial seizure the patient maintains consciousness but may have sudden, unexplained emotions or sensations.

A complex partial seizure causes an altered state of consciousness or loss of consciousness. Patients may engage in unusual repetitious behavior.Locating the Source of Seizures There is no cure for epilepsy. There are several different types of medications for controlling/reducing seizure activity. However, half of all patients continue to have some degree of symptoms. For some, the seizures can be severe and significantly interfere with their quality of life.One option that may be available for patients with uncontrolled seizures is surgery.

Doctors destroy the brain cells in the area where the seizures originate, hopefully eradicating the problem. While surgery can be a very effective treatment, patients must be carefully selected. The seizure activity must be limited to a specific area of the brain and doctors must be able to clearly identify that location.The traditional method to identify the location of seizures is through EEG (electroencephalography) monitoring; 19 to 25 electrodes are placed over various spots on the scalp. The electrodes measure the electrical activity of the brain.

When a seizure occurs, the electrodes pick up the electrical activity throughout the brain. The location of the abnormal signals can be determined by comparing the signals detected by each electrode.EEG monitoring can help confirm a seizure is limited to one side of the brain. However, it only gives a rough indication of the precise location of the abnormal electrical activity. Currently, the only way to pinpoint the precise area of activity is by opening the skull and placing electrodes directly onto the surface of the brain.

The Geodesic EEG A new type of EEG monitoring is called Geodesic EEG. The Geodesic EEG system is a net of 128 to 256 electrodes draped over the patient’s head. The Geodesic electrodes measure brain activity in the same way as standard EEG. However, with so many electrodes and having them spaced much closer together, doctors can get more precise information on the location of seizures.

The Geodesic EEG was approved for brain monitoring by the FDA in 2001. However, doctors are still comparing its effectiveness against invasive brain monitoring. If the procedure proves to be just as accurate, some patients may be able to avoid direct brain surface monitoring. Doctors will then be able to use the information from the Geodesic EEG to determine if a patient is a good candidate for epilepsy surgery.