The "gold standard" in the diagnosis of nonepileptic seizures (NESs) is a recording of a typical event during video-EEG monitoring. This procedure is available at all centers specializing in epilepsy and is increasingly available at general hospitals and even in some neurologic group practices.
During this procedure, the EEG is recorded for a prolonged period, accompanied by continuous closed-circuit video observation. The digitized EEG and recorded behavior are displayed simultaneously, allowing point-to-point correlations of recorded events and any accompanying electrographic changes.
Video-EEG findings
During NESs, the EEG will show:
-no epileptiform activity
-no initial change such as premonitory spikes
-no postseizure slowing
Although the EEG tracing is frequently obscured by movement artifact, small interpretable segments containing alpha activity may be apparent, indicating that consciousness is preserved.
A normal or nonepileptiform EEG during a seizure may suggest a NES, but it can also occur during a simple partial seizure or frontal lobe complex partial seizure undetected by surface leads. A normal EEG during a seizure in which the patient is displaying generalized motor movements would not be expected in a true epileptic seizure, however.
The most important task is to ensure that the recorded event(s) are typical of the patient's spontaneous attacks. This task can be accomplished only by reviewing the recorded attack with a person who has witnessed such events. If it is determined that the recorded and spontaneous attacks are similar, a presumptive diagnosis of NESs can be made.
Some clinicians require that more than one attack be recorded, but this is not always possible. Nonetheless, it appears that a single recorded event similar to previous attacks is sufficient to consider NESs the most likely diagnosis.
This diagnosis, of course, does not exclude the possibility of coexisting epilepsy, especially if the patient has attacks with different clinical features. Some epilepsy patients experience psychogenic nonepileptic seizures at some point, and patients with psychogenic nonepileptic seizures can have neurologic illness.
The interictal EEG is not useful in making the distinction because it may be normal or abnormal in either case. The interictal EEG of patients with NESs may contain epileptiform discharges, even though the ictal record does not reveal electrographic seizure activity.
