Getting the Diagnosis Right
If a person has not been previously evaluated, we first determine if he or she actually has epilepsy. Once epilepsy is diagnosed, we conduct various tests to classify the type of epilepsy the person has.
Stage 1: Initial History, Exam, and Tests. This includes a thorough neurological history, neurological exam, and preliminary tests such as an EEG, MRI, and blood tests.
Stage 2: Long-Term EEG Monitoring. Depending on the patient, monitoring may be done at home or in the hospital's Epilepsy Monitoring Unit.
Stage 3: Surgery Evaluation, if Required. If previous evaluation suggests that surgery is an option, other tests will be needed.
On the first visit, the patient may be given a thorough neurological evaluation with one or more of these preliminary tests:
- EEG. Electroencephalography (EEG) is the recording of the brain's electrical activity. Epileptic "brain waves", spikes and seizures, provide objective evidence to help diagnose, classify, and localize the origin of a patient's seizures.
- MRI. Magnetic resonance imaging (MRI) is a scan of the brain's structure that can show tumors, abnormal blood vessels, cysts, areas of brain cell loss, and other brain damage that may be the cause of seizures.
- Blood tests. If the patient is currently taking seizure medications and, in particular, experiencing side effects, blood is sampled to measure the concentration of anti-epileptic drugs and to determine if these drugs are present in a therapeutic range.
We are often able to make a proper diagnosis after these steps. Other patients will need to have additional monitoring.
EEG abnormalities, like seizures, may be intermittent and, consequently, missed in a routine 30-to-60-minute EEG. When a patient appears to have epilepsy but has a normal or non-epileptic EEG, the next step is record the EEG for a longer time.
Long-term EEG monitoring may be done on an outpatient or inpatient basis depending on the individual.
- Ambulatory EEG monitoring. The patient is connected to a small, portable EEG recorder that can be worn throughout daily activities and sleep. This type of monitoring usually lasts 24 to 48 hours. The patient continues to take medication throughout this period.
- Simultaneous EEG recording and video (TV) monitoring. The patient is admitted to the hospital of the University of Chicago Medicine for long-term EEG recording and simultaneous video monitoring of behavior. This evaluation can last from a few days to over a week. During this time, anti-epileptic drugs are gradually withdrawn so seizures will occur more frequently, but in a safe, controlled setting. Brain activity is recorded during seizures, and the patient's behavior is monitored closely.
If surgery is being considered, additional advanced tests will be performed to locate the source of the seizures. These may include the following:
- Long-Term EEG recording and simultaneous video (TV) monitoring. The same advanced EEG/video monitoring used for diagnosis is used for surgical evaluation. The difference lies in the amount of data collected and how it is analyzed. The goal of pre-surgical EEG monitoring is to determine if seizures come from only one area of the brain and, if so, precisely where they originate.
- Neuropsychological testing. These tests are done by our neuropsychologists to determine objectively if there are any deficits in the patient's memory and language functions and, if such deficits exist, in which part of the brain the abnormality is located. This profile is critical to identifying any potential risks of surgery. Findings help locate the epileptic focus and help determine the type of surgery performed.
- EEG and MRI three-dimensional source models. Using data from EEG monitoring and MRI scans, our mapping experts use computers to create a 3-D model of the patient's epileptic focus and brain.
- Intracarotid sodium amobarbital testing. In this procedure, each half of the brain is put to sleep for a brief period of time. An anesthetic drug is injected into the carotid artery in the neck by a radiologist during a routine angiogram of the brain. An EEG performed at the same time verifies that each side of the brain is asleep after the injection and for how long. Testing by neuropsychologists during the procedure determines in which half of the brain the speech center resides and how well each side of the brain can form memories. These data further verify the information obtained in prior neuropsychological testing.
- Invasive electrode implantation. In some cases, surgery appears to be a good option, but the location of the patient's seizures cannot be determined precisely even after the full battery of noninvasive testing and analyses. Invasive electrode implantation is usually recommended in these instances. Electrodes are placed on the patient's brain in a surgical procedure. The EEG signals from these intracranial electrodes are monitored for several days until seizures are recorded and their origin determined.