Epilepsy

Diagnosis

The first step in evaluation is an accurate diagnosis. Other conditions may be confused with epilepsy, such as syncope (fainting), stroke and certain psychological disorders.

Several tests are used in the evaluation of epilepsy.

Electroencephalography (EEG)

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Video-EEG monitoring

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Electroencephalography (EEG)

EEG records a patient's brain wave activity. In patients with epilepsy, the electrical activity of the brain is disturbed. That disturbance may be detected by EEG. The pattern of brain wave activity may help physicians diagnose seizure type. In patients with partial epilepsy, EEG may also help physicians pinpoint the area of seizure onset.

During EEG, a series of 32 electrodes are placed on the patient's scalp to record the brain's electrical activity. An EEG appointment takes one to two hours. The effectiveness of EEG in determining epilepsy is higher if the patient is asleep. Patients are encouraged to limit their sleep the night before testing to four to six hours, so that they are more likely to sleep during the study. Sedation overseen by trained nursing staff is available for pediatric patients.

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Inpatient Video-EEG Monitoring

For patients being evaluated for epilepsy surgery, inpatient video-EEG monitoring is used to find the brain location where seizures begin. When the diagnosis is uncertain, monitoring may also be used to confirm or rule out epilepsy. Continuous monitoring helps identify the focus and type of the seizures the patient experiences. Inpatient video-EEG monitoring may detect previously undiagnosed seizures in up to 20 percent of patients who undergo the procedure.

More than 1,000 adult and pediatric patients are evaluated in the monitoring units at Mayo Clinic each year. The average hospital stay in the EEG monitoring unit ranges from four to seven days. Patients are typically monitored long enough to record at least three seizures.

Mayo Clinic EEG monitoring units are open 24 hours a day, seven days a week. They are hospital-based, so that medication can be reduced, if necessary, to record a seizure.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging provides details about the brain. MRI may detect certain lesions (diseased tissue) in the brain that cause seizures. MRI also helps specialists diagnose the causes of epilepsy and evaluate potential candidates for surgery.

Brain abnormalities may be subtle. Specialized MRI scanning may detect asymmetries (dissimilar corresponding parts on opposite sides that are normally alike) in the brain that indicate the side of the brain where seizures begin.

Researchers at Mayo Clinic have developed several MRI techniques to evaluate patients with epilepsy. A typical MRI takes approximately 45 minutes.

Positron Emission Tomography (PET)

Positron emission tomography, a noninvasive, three-dimensional imaging technique, may be helpful for patients who have partial seizures when MRI does not prove an abnormality is causing the problem.

SISCOM imaging technology helps physicians identify the area where the greatest amount of brain activity is taking place during a seizure.

SISCOM (Subtraction Ictal SPECT Co-registered to MRI) is an imaging technology developed at Mayo Clinic. SISCOM precisely pinpoints seizure hot spots in patients with epilepsy, allowing specialists to determine the most appropriate surgical treatment options. SISCOM is used primarily for patients being evaluated for epilepsy surgery when the area of seizure onset is not clear on EEG or MRI.

SISCOM diagnosis requires that the patient be admitted to the hospital for one week. The patient is monitored constantly. When a seizure occurs, a tracer carrying a small amount of radioactivity is immediately injected into the patient's bloodstream. The tracer tags red blood cells at the site in the brain where the seizure originated. A scan is taken to show the cells the tracer has tagged. A second scan is taken 24 hours later, while the patient is seizure free. The two scans are compared to confirm the seizure hot spot.

Differences between the two scans are difficult to detect with the human eye. As part of SISCOM, Mayo Clinic physicians and scientists developed a computer program that electronically subtracts one image of the patient's brain from the other image, leaving a clear picture of the seizure hot spot. The subtracted image of the brain is then superimposed on an MRI scan to map the hot spot's location. In many cases, SISCOM identifies the patient's seizure focal point for the first time.

Neuropsychological Testing

Neuropsychological testing measures a patient's memory and cognition. One example of this testing is or neuropsychological testing is the intelligence quotient (IQ) test.

Neuropsychological testing may help identify areas of the brain that are not functioning normally. Dysfunction may provide a clue to the area of seizure onset.

Because one risk of epilepsy surgery is its effects on memory and cognition, baseline neuropsychological testing may be included as a component of evaluation before surgery.