The diagnosis of epilepsy is often not straightforward, and misdiagnosis is not rare . A detailed and reliable account of the event by an eyewitness is the most important part of the diagnostic evaluation, but may not be available .
Electroencephalography (EEG) is an important diagnostic test in evaluating a patient with possible epilepsy. It can provide support for the diagnosis of epilepsy and also assists in classifying the underlying epileptic syndrome.
However, there are several reasons why EEG alone cannot be used to make or refute a specific diagnosis of epilepsy:
- Most EEG patterns can be caused by a wide variety of different neurologic diseases.
- Many diseases can cause more than one type of EEG pattern.
- Intermittent EEG changes, including interictal epileptiform discharges, can be infrequent and may not appear during the relatively brief period of routine EEG recording.
- The EEG can be abnormal in some persons with no other evidence of disease.
- Not all cases of brain disease are associated with an EEG abnormality, particularly if the pathology is small, chronic, or located deep in the brain.
In order to make the best clinical use of EEG in the evaluation of patients with possible epilepsy, the clinician must understand the strengths and weaknesses of EEG, specifically as they relate to the diagnosis of seizures and epilepsy.