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Epilepsy is a chronic brain disorder in which a patient has recurrent seizures throughout their life. The seizures are caused by abnormal electrical activity of certain cells in the brain.
Approximately three million people in the United States are affected by epilepsy, with approximately 200,000 new cases of seizures and epilepsy occurring each year. Ten percent of the American population will experience a seizure in their lifetime, and three percent will develop epilepsy by age 75.
Source: Epilepsy Foundation 2009
When epilepsy is suspected, a patient is evaluated with a complete physical and neurological examination and a thorough seizure history. Most of the tests are to identify the precise location and extent of the seizure focus, the character of the seizures, and the relationship of the seizure focus to other brain functions, such as speech. How many tests have to be done depends on the type of treatment being planned and how much information each test produces.
MRI forms the mainstay of imaging for epilepsy, and increasingly functional MRI and magnetic resonance spectroscopy are utilized for structural lesions, but may often fail to localize the seizure focus.
Seizures are the result of abnormal “synchronized firing” of a cluster of brain cells. These cells become very metabolically 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. During a seizure, the PET/CT scan shows the area responsible for the seizure as an area of increased glucose use. Between the seizures, PET/CT shows a characteristic pattern of reduced need for glucose. PET/CT imaging, especially when performed concurrently with surface EEG measurements, may be useful for localizing all of the seizure foci for surgical resection.
Accurate localization of the focus of the seizure activity is critically important to determine treatment options.
Medications are available that will reduce the frequency and severity of seizures in many patients, and this is the preferred method of treatment.
Patients whose seizures cannot be controlled by medication are referred to as patients with intractable seizures. For these patients surgery may be an option if their seizures are localized to a small part of the brain. Successful surgery has been found to stop the seizures completely or at least significantly reduce them, enabling patients to resume normal activities. If surgery is determined to be the best option for treatment, the patient and the family should communicate with their physician to have a realistic picture of the benefits, the risks, and the chances of complete or partial control of seizures afterwards.
Accurate identification of the location of the brain tissue involved in causing the seizures is critical. By helping the physician identify the source of the seizure activity within the brain, PET/CT imaging provides an additional test to help plan the surgery.
Accurate localization of the focus of the seizure activity is critically important for surgical treatment.
After surgery, patients should undergo a comprehensive postoperative evaluation, and physicians will schedule routine follow-up visits to determine if the symptoms have improved or are cured. There may be physical after-effects or emotional changes following surgery which should be discussed with family and the medical team. Physicians may recommend outpatient rehabilitative care, including help to the transition to a seizure-free or almost seizure-free lifestyle with respect to psychological and social adjustment, education, and vocational training.
Early research and clinical applications of PET imaging were almost exclusively devoted to the brain, and provided immense amounts of data that have advanced our understanding of brain function and changes in regional glucose metabolism.
Source: Atlas of Clinical Positron Emission Tomography by Sallie F. Barrington, Michael N. Maisey and Richard R. Wahl. Oxford University Press, Inc. New York, NY.
