Epilepsy

Seizures are the result of abnormal "synchronized firing" of a cluster of brain cells. These cells become metabolically very active during the seizure, and in most patients remain less active than normal brain tissue between seizures. How the seizures present in symptoms differs depending on which part of the brain is involved. If surgery is determined to be the best option for treatment, accurate identification of the location of the brain tissue involved is critical. Identifying the source of the seizure activity within the brain may lead to a surgical removal of this tissue, enabling the seizures to be stopped completely or at least reduced significantly.

Using an imaging drug that is like glucose (sugar), the PET scan will show how the tissues in the brain are functioning (See How PET Works). Areas of less function use less energy, and areas with increased metabolic activity use more energy. The PET scan shows those differences in functional activity. During a seizure, the area responsible for the seizure will show up as an area of increased glucose use. Between the seizures, PET shows a characteristic pattern of reduced need for glucose.

PET FDG imaging, especially when performed concurrently with surface EEG measurements, may be useful for localizing all of the seizure foci for surgical resection. Without PET, patients would be forced to have an invasive procedure that requires depth electrodes being placed directly on the surface of the brain so that the electrical activity can be measured over a period of time. For the many patients that can be controlled by modern medications, surgery would not be considered. However, for those that cannot be controlled, PET provides an alternative test to help plan the surgery.

PET is a very useful test when doctors are identifying the source of seizure activity in the brain because it can non-invasively identify the metabolic focus for possible surgical removal and determine if there is more than one focus.