Diagnosis of Epilepsy & Seizures
Patients should be evaluated thoroughly after an initial seizure. It is imperative that the clinician take a complete and detailed patient history, including details of birth, childhood, family history, and medication regimen; and a thorough medical history, including any illnesses of the nervous system. In some cases, other conditions (e.g., irregular heartbeat) must be ruled out. A thorough history of drug and alcohol use is equally important.
It also is helpful to distinguish seizure subtypes, partial or generalized; time of day of the event, including whether the seizure occurred during wakefulness or sleep; and any known triggers, such as a flickering light, severe sleep deprivation, or dehydration.
Thorough general physical and detailed neurological examinations also should be performed.
Diagnostic Testing for Epilepsy
Laboratory data utilized in the diagnostic evaluation of patients with seizure disorders may include CAT scan imaging, magnetic resonance imaging (MRI), and electroencephalography (EEG). A complete blood laboratory panel, including drug-toxic screening, and urinalysis are usually performed.
CAT scan brain imaging is often the first radiological study obtained, especially in the emergency room setting. It can indicate pathology such as a brain tumor, stroke, brain hemorrhage, acute or remote trauma, and infection. Limitations include inability to evaluate certain structures in the brain in detail, particularly the temporal lobes of the brain, often the first sites of seizure activity.
MRI brain imaging is performed for many patients with seizure disorders. It has the ability to visualize in great detail much of our brain anatomy. Subtle asymmetries in relevant structures, as well as undetected mass lesions, small strokes, and evidence of trauma may be uncovered. The use of a contrast agent (injected into the vein) can enhance the ability to show underlying abnormalities.
EEG (also known as "brain wave") provides information about the electrical activity in the brain. Unlike CAT or MRI, it does not produce an image of the brain, but supplies information about the function or dysfunction of parts of the brain. Multiple small electrodes are placed at specific points on the scalp on both sides of the head to record activity generated mainly by the cerebral cortex. Brain wave activity is usually recorded for 30-45 minutes.
Many patients will also be tested while hyperventilating (breathing rapidly and deeply), when flashing lights are flashing, while sleeping, or when sleep deprived. The brain normally exhibits particular patterns on the EEG during wakefulness, drowsiness, and sleep. The duration and character of normal brain-wave activity can be used as a baseline for comparison with abnormal waves on an EEG.
Some of the findings on EEG are specific to particular disorders and subtypes of epilepsy. Activity during a seizure can be identified by a pattern on the graph indicating epilepsy called epileptiform. Correlating this type of data with clinical symptoms of seizures often helps make an accurate diagnosis. The EEG recording between seizures is often abnormal in patients with epilepsy, and so can be helpful in this setting.
EEG can be combined with video monitoring to record activity both electrically and visually. EEG can also be performed in a long-term care setting with a portable ambulatory unit, to monitor patients for up to many days at a time.
Other uses of the EEG include evaluation of altered states of consciousness, brain damage, metabolic-toxic injury, and suspected brain death.