MEG and Brain Mapping to Diagnose Epilepsy
Advanced Brain Mapping
Froedtert & the Medical College of Wisconsin have played a pioneering role in the development and innovative use of advanced diagnostic techniques to map the functional areas in the brain prior to surgery. These highly specialized tests are performed by interventional radiologists, epileptologists and neuropsychologists. These tests are performed while the patient is awake and reduce the risk of loss of speech and memory functions and help in deciding on surgery as a treatment. This results in a higher level of care for neurology and neurosurgery patients.
Intracarotid Sodium Amobarbital Test
This test determines which side of the brain is responsible for vital cognitive functions. A drug is injected into first one hemisphere of the brain and then the other hemisphere. Knowing whether the left or right side of the brain supports language and memory helps with making decisions on surgery to treat epileptic seizures.
Functional Magnetic Resonance Imaging (fMRI)
This specialized MRI scan maps the different types of functions, like language, memory, attention, motor and the visual processes. It provides detailed images quickly and moment-to-moment changes in brain activity. The fMRI allows surgeons to pinpoint the functional areas of the brain and to improve outcome following surgery.
Video EEG Monitoring
Epilepsy is known as a "historical disease" because doctors generally don't have the opportunity to observe seizures — they have to rely on the patient's description. For some patients with epilepsy, whose seizures respond well to medication, this "historical" information is sufficient. But when medications are not effective (a condition known as refractory epilepsy), a higher level of diagnostic care and treatment is called for.
In such cases, patients are admitted to the hospital for video EEG monitoring. During this procedure, the patient is connected to EEG monitoring equipment. The equipment receives the EEG read-out, translates it into digital format and merges it with simultaneous digital video recording, allowing for a continuous record of seizures over several days.
A technologist monitors the recording, and an online computer monitors the EEG changes. Such monitoring allows the physician to diagnose the type, frequency, and precise location of patients' seizures.
Magnetoencephalograhy (MEG) in Epilepsy Patients
Successful surgical treatment depends on accurately determining the region of seizure onset—the epileptogenic zone—and its relationship to functionally important brain areas.
Non-invasive techniques to locate the epileptogenic zone and functional cortex can be of enormous value in guiding epilepsy surgery.
The source of seizures is unique in each person with epilepsy. MEG provides a non-invasive way to localize the areas of the brain that show evidence of electrical irritability with a high spatial precision. The high temporal resolution of MEG also allows the epileptologists to distinguish between areas from which abnormal electrical discharges originate and those to which they propagate. MEG can also be utilized to identify areas important for motor function, language or vision, and their relationship to abnormal areas.
In epilepsy patients, a MEG study can:
- Make it unnecessary to perform an invasive recording of brain electrical activity in some patients, thereby decreasing hospital stays.
- Identify potential areas of electrical abnormalities, and thereby allow better placement of intracranial electrodes in other patients.
- Allow patients to make better-informed decisions about pursuing surgical treatment, given the relationship between abnormal areas and important brain functions identified non-invasively using MEG.
Learn more about MEG
Other Advanced Diagnostics
In addition to video EEG monitoring, the Comprehensive Epilepsy Program uses several advanced neuro-imaging strategies to evaluate patients' seizures and determine whether they are most likely to benefit from surgery or other treatment options. These include:
- Magnetic resonance imaging (MRI), a scanning technique with special high resolution imaging protocols specifically designed for patients with epilepsy.
- Brain Single Photon Emission Computerized Tomography (SPECT) scanning, a method of tracking blood flow through the brain to identify the location of seizure activity.
- Positron Emission Tomography (PET), that provides an image of the metabolic state of the brain.