Epilepsy

Diagnosis

Other conditions may be confused with epilepsy, such as syncope, stroke, and certain psychological disorders. The first step in evaluation is an accurate diagnosis. Once epilepsy is diagnosed, identifying the cause and determining treatment are the next priorities. Test results are usually available within hours in Mayo's state-of-the-art electronic medical record.

Several tests are used in the evaluation of epilepsy.

Electroencephalography (EEG)

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

During an 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 the 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.

Inpatient Video-EEG Monitoring

Inpatient video-EEG monitoring

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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 seizure. Inpatient video-EEG monitoring has been shown to detect previously undiagnosed seizures in up to 20 percent of patients who undergo the procedure.

Video-EEG monitoring is available at all three Mayo Clinic sites. 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. The EEG monitoring units are open 24 hours a day, seven days a week and are hospital-based, so that medication can be reduced, if necessary, to record a seizure.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging allows detailed imaging of the brain. MRI has greatly enhanced the ability to detect certain lesions in the brain that cause seizures. (Lesion is defined as any diseased tissue.) MRI is important in diagnosing the causes of epilepsy, and in evaluating potential candidates for surgery. Specialized MRI scanning may detect very subtle asymmetries in the brain that indicate the side of the brain where seizures start.

Researchers at Mayo Clinic have developed several techniques to evaluate patients with epilepsy. Abnormalities can be subtle, and may go undetected unless these techniques are used. A typical MRI takes approximately 45 minutes.

Positron Emission Tomography (PET)

PET is potentially helpful in patients who have partial seizures but the MRI does not prove an abnormality is causing the problem.

SISCOM helps physicians zero in on the area of the brain where the greatest amount of activity is taking place during a seizure.

SISCOM

SISCOM (Subtraction Ictal SPECT Co-registered to MRI) is an imaging technology developed by Mayo Clinic to precisely pinpoint seizure hotspots in patients with epilepsy and provide better surgical treatment options. Only a few medical centers in the world offer this diagnostic option. Primarily, the test is used in patients being evaluated for epilepsy surgery when the area of seizure onset is not clear on MRI or EEG.

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

Since differences between the two scans are difficult to detect with the human eye, a computer program developed by a team of Mayo Clinic physicians and scientists 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 onto an MRI scan to map the hot spot's physical location. In many cases, the seizure focal point may become evident for the first time.

Neuropsychological Testing

Neuropsychological testing measures a patient's memory and cognition. The most familiar example is the IQ test. Neuropsychological testing can sometimes help identify areas of the brain that are not functioning normally. Dysfunction may provide a clue as to the area of seizure onset. For example, impaired memory for word lists may indicate abnormal left temporal function.

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