Tests & Procedures
Electroencephalograph (EEG) records the electrical activity in the brain. Electrodes are pasted to the patient’s head in specific places, and wires are then connected from the electrodes to an EEG machine. Brain wave activity may show a pattern, which helps the doctor determine whether or not someone has epilepsy. Sharp waves support the diagnosis of epilepsy and can help identify the type of epilepsy.
Magnetic Resonance Imaging (MRI) or Computerized Tomography (CT) scan may be performed to look for any growths, scarring, or other conditions in the brain that may be causing seizures.
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Diagnostic Video EEG Monitoring is used to diagnose patients who do not respond to epilepsy medications. Video EEG monitoring is continuous EEG monitoring and continuous videotaping of the patient. This monitoring is usually performed in the hospital over several days. This allows the doctor to observe the behavior that occurs during the seizure and how it is related to the electrical activity in the brain. Often the patient’s anti-epileptic medication is reduced to allow seizures to occur so they can be recorded. Video EEG monitoring can help to:
- Confirm the diagnosis of epilepsy
- Determine the type of epilepsy and the best medication for it
- Allow medication change under supervision
- Pinpoint the region of the brain where the seizures begin, which is essential if epilepsy surgery is being considered
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Epilepsy Surgery Candidate Evaluation
Some people who do not respond to anti-epileptic medications may benefit from epilepsy surgery—50 to 80 percent of patients who are suitable candidates for surgery are seizure-free after surgery. Proper patient selection and a thorough pre-surgical evaluation are the cornerstones of surgical success. The pre-surgical evaluation is a relatively lengthy process which may take several months.
The following tests may be included in the pre-surgical evaluation:
PET scan (Positron Emission Tomography) shows the brain's use of oxygen or sugar (glucose). A very low, safe dose of a radioactive substance is injected into a vein in the arm, and the scanner records its circulation. The image shows areas of the brain that are more active than others. This test can help identify the area(s) of the brain where partial seizures begin.
Ictal SPECT (Single Photon Emission Computed Tomography) is a scan that shows the blood flow in the brain and is used to locate the site where the seizure begins. A very low, safe dose of a radioactive substance is injected into a vein in the arm as soon as possible after a seizure begins. The scan is performed soon afterwards. An image is produced which highlights the area of greatest blood flow during the seizure.
Neuropsychological testing measures a person’s memory and cognition. Neuropsychological testing can sometimes help identify areas of the brain that are not functioning normally, which may provide a clue to the area where the seizure begins. For example, impaired memory for words may indicate abnormal left temporal function.
Magneto-encephalography (MEG) measures electrical currents in the brain. MEG is similar to an EEG but is much more accurate. When it is combined with MRI, it is extremely helpful for identifying areas of the brain where the seizure begins.
Functional MRI (fMRI) is a brain scan that evaluates the structure of the brain that is responsible for movement or sensation activity. The person will be asked to look at pictures, listen to sounds, or squeeze a ball during the scan, and the image will highlight the area of the brain engaged in the task.
WADA test is performed during and angiogram to determine which side of the brain is responsible for language and memory. A medicine will be injected to put one side of the brain to sleep at a time. The patient is asked to read and talk during the exam.
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Note: In about 10 percent of patients, the evaluation workup may be inconclusive regarding the exact location of seizure onset. Therefore, in a small number of patients, it may be necessary to insert electrodes directly in or on the brain. Electrodes are placed on the brain using subdural grids or into the brain using depth electrodes to precisely record the seizure onset. These special electrodes provide more accurate information than EEG studies with electrodes on the scalp because they are physically closer to the origin of the seizure. The procedure to place the electrodes occurs in the operating room and typically lasts 4 to 5 hours. The patient will have several wires coming through the scalp, and the head will be wrapped in gauze. Immediately after the procedure, the patient will spend the night in the neurosurgical intensive care unit for close monitoring. The following day, the patient will be transferred to the Epilepsy Monitoring Unit (EMU) for video EEG monitoring. The patient usually spends 7 to 10 days in the EMU. While there, the anti-epileptic medications will be reduced. After several seizures have occurred and have been recorded, the medications are restarted. The doctors then review the video EEG monitoring information and determine if the seizure location has been identified and if it is an area of the brain that can be removed. The electrodes are then removed in the operating room during the resection of the area causing the seizure.
The Epilepsy Management Conference
The test results are presented at a multidisciplinary Epilepsy Management Conference. The team includes a neurologist, neurosurgeon, neuroradiologist, nuclear medicine physician, neuropsychologist, psychiatrist, epilepsy nurses and technicians. The group will decide if the patient is a good candidate for epilepsy surgery and weigh the risks and benefits of surgery.
If the patient is a candidate for surgery, the neurosurgeon will discuss the details of the procedure, the associated risks and postoperative care. With the patient’s consent, a date for the surgery will be scheduled. The patient will then undergo the pre-surgical exams, such as chest x-ray and EKG, to evaluate for any medical conditions which may cause a risk for surgery.