Diagnostic Testing for Epilepsy
The right diagnosis is critical to epilepsy treatment
Not all seizures are epileptic in origin. In order to make an initial diagnosis, your patient care will begin with a complete evaluation to rule out other causes. We diagnose epilepsy using a number of techniques, including:
- CT (computed tomography)
- MRI (magnetic resonance imaging)
- EEG recording (Electroencephalography or brainwave recordings)
- 24-hour video EEG monitoring
- Neuropsychological tests
- Wada testing
Neuropsychological testing is used to assess cognitive abilities such as memory, language and problem solving. Your test results can be used to help determine the location of your seizures.
In addition, neuropsychological test results (in conjunction with Wada testing) can provide additional information regarding probable cognitive outcomes and the likelihood of being seizure free after surgery.
The neuropsychological evaluation consists of an interview with a neuropsychologist, followed by five to six hours of cognitive testing. It is often beneficial to have a family member present during the clinical interview to provide additional information regarding your seizures.
If you undergo neurosurgery, a follow-up neuropsychological evaluation will be conducted approximately six months after surgery. This post-operative assessment provides you with information about areas of cognitive change and provides us with important outcome information for the epilepsy surgery program.
The Wada Test is part of the pre-surgical evaluation of epilepsy. During the Wada test, each cerebral hemisphere (half of the brain) is anesthetized separately to allow for testing of the opposite hemisphere.
This procedure can establish which hemisphere (side of the brain) is dominant for language and can determine if a single hemisphere can support memory function. Results from Wada testing and a neuropsychological evaluation can provide important information regarding cognitive and seizure outcome.
What is involved with this procedure:
- Electrodes will be placed on your scalp so that an EEG recording can be done during Wada testing.
- An IV is started and blood work is done.
- Baseline language and memory testing are completed. Your memory is tested by showing you eight objects to remember. After that, we test basic language functions such as comprehension, naming, repetition, and reading. After language testing is finished, you will be shown the eight objects mixed in with a group of 16 objects to see if you can selectively recognize any of the memory objects. This brief memory and language assessment is repeated twice more during the actual Wada test.
- After baseline testing of memory and language, a cerebral angiogram is done. Cerebral angiography is a way of taking X-ray pictures of the arteries in the brain. X-ray dye in injected into the arteries through a catheter. This allows them to be seen on x-rays.
- Wada testing begins after the angiogram is completed. Amobarbital is given via the catheter to put half your brain to sleep for approximately 10 minutes. During that brief time, we show you eight new objects and then test your language functions again. Once the medications have worn off and your EEG, language, and motor functions have returned to normal, we test your recall and recognition of the objects.
- Wada testing continues as the other half of the brain is put to sleep and the whole memory and language procedure is repeated using eight different objects.
The angiogram and Wada testing take approximately two hours. A neuroradiologist, interventional radiology technician, EEG technician, neuropsychologist and psychometrist are all present during your testing.
After the Wada test is complete, you will be monitored closely for 4-6 hours. You will be discharged later that day after a post-monitoring recovery period. During this recovery period, the neuropsychologist will review the results of the Wada test with you and your family.
Patients whose seizures can’t be controlled with medications, and those who may be candidates for epilepsy surgery, are often scheduled for long-term epilepsy monitoring.
Long term epilepsy monitoring (LTEM) involves the simultaneous use of video and EEG recordings during your hospital stay. Video-EEG monitoring provides the most detailed information regarding brainwaves and behavior during seizures.
Information from the study is used to determine if surgery is a viable treatment or if other options should be considered. This information helps to:
- Establish an epilepsy diagnosis: In most epilepsy centers, about 1 in 4 patients who have seizure-like events do not have epilepsy.
- Identify the seizure type: Some seizure medications are designed to treat certain types of seizures.
- Locate the source: Monitoring can help identify the brain area where your seizures begin. Lateralization and localization (finding the side and area) of your seizures is a critical first step in planning any epilepsy surgery. Seizures are videotaped because your behavior during seizures can also help to locate the source.
- Determine seizure frequency: Video-EEG monitoring can identify how often you are having seizures. Frequently patients have seizures and don’t know unless someone tells them.
Your epilepsy monitoring study will take place in a private room equipped with a special video electroencephalography (EEG) equipment. Long term monitoring is conducted over several days and includes 24-hour recording of your brain activity and behavior during seizures.
Your antiepileptic drugs may be adjusted and you may be exposed to other stressors (light, sound, sleep deprivation) in order to trigger your seizures. On average, long-term monitoring takes five to seven days.