Laboratory and non-laboratory tests are used to diagnose and monitor epilepsy, to determine what kind(s) of seizures a person is having, to identify underlying conditions such as toxins, infections, drug or alcohol withdrawal, fever (in a child), or diabetes that may be causing seizures, and to distinguish epilepsy from conditions such as fainting or a stroke that may cause some of the same symptoms.
A medical history, input from the patient, and input from family members who have witnessed the seizures are important parts of the diagnostic process. Someone with epilepsy may remember a strange smell, an aura, and/or sensations that precede a seizure but may not remember what has happened during the seizure itself. Depending upon the signs and frequency of a person's seizures, it may take some time to determine the proper diagnosis.
- Electroencephalogram (EEG) – the primary diagnostic tool for epilepsy; it is used to evaluate the brain's electrical activity and identify changes in brain wave patterns.
- Computed tomography (CT) – identifies brain structure abnormalities and tumors
- Magnetic resonance imaging (MRI) – also identifies brain abnormalities
- Positron emission tomography (PET) – radioactive material is used to look at active areas of the brain
- Single-photon emission computed tomography (SPECT) – radioactive material is used to identify the region of the brain where seizures originate when it is not clear on other scans
Laboratory tests are primarily used to monitor anti-epileptic medications and to search for conditions that may cause seizures, such as diabetes, infection, meningitis or encephalitis.
Periodic therapeutic drug monitoring is performed when a patient is taking a specific medication to ensure that therapeutic levels are achieved. Epileptic medications that are monitored include:
There are some newer second-generation antiepileptic drugs, such as levetiracetam, that usually do not require routine monitoring but may be tested in order to evaluate and adjust dosage as necessary.
Other testing is done to identify possible causes for seizures, including:
- Complete blood count (CBC) – to evaluate blood cells to check for a variety of conditions, including infection
- Glucose – to check for the possibility of diabetes
- CSF analysis – to check for infection and help diagnose meningitis and encephalitis
- Blood culture – to check for septicemia, infection in the blood
- Drug abuse testing—to detect drugs and/or alcohol (ethanol)