Epilepsy monitoring is also used to capture spells, which may be epileptic, psychogenic non-epileptic, or physiologic non-epileptic (sometimes referred to as spell characterization). The differentiation between these is crucial because psychogenic non-epileptic episodes/events (PNEE) and physiologic non-epileptic events do not require treatment with AEDs. In fact, many patients with spells are referred to a neurologist or epileptologist to determine if their spells are really epileptic. Generally, these patients first undergo a routine EEG. If that does not yield enough information, an EMU stay is ordered (although in some cases a shorter outpatient video-EEG can be done if the patient’s spells are very frequent). The gold standard for the diagnosis of psychogenic non-epileptic events is video-EEG.
There is a small subset of patients who have both epileptic and non-epileptic events (mixed disorder). In this situation an EMU stay is pivotal to differentiate the two types of events.
The information gained from an EMU stay may allow, in appropriate cases, AEDs to be tapered off. This prevents unnecessary treatment, associated side effects, and can reduce utilization of health care services. For instance, many patients have made repeated trips to the emergency department because of breakthrough seizure-like events and been placed on AEDs, which are later determined not to be needed as the events are found to be psychogenic or physiologic in origin after an EMU evaluation.
What Happens in an EMU?
Most of the time, a situation is created in the EMU to induce a seizure or event or make one more likely to occur. This is done by tapering or stopping AEDs. Other activation techniques include, but are not limited to, photic stimulation, hyperventilation, and sleep deprivation. The number of events or seizures that need to be recorded depends on the clinical situation and is often more than one; for a patient with multiple types of episodes it is usually one of each type.
An EMU stay can be performed when a patient is not responding to AED therapy. In this case the EMU stay can verify the diagnosis, as the patient could be experiencing refractory or drug resistant epilepsy or non-epileptic events.
While an EMU stay can reveal much that is clinically relevant, it is not always all telling. Sometimes an event cannot be captured despite AED withdrawal and seizure activation attempts, or an event is captured but there are no associated EEG changes. This does not necessarily exclude the seizure, as some types of seizures cannot be picked up on scalp EEG. Therefore, the EMU result has to be interpreted with the rest of the history. Moreover, there are situations in which the EMU stay may need to be repeated, such as in the above case where the study comes back negative, or when patients have a notable change in their seizure/episode type or frequency.
The above discussion demonstrates that video-EEG in the setting of the EMU is an intricate diagnostic modality with more than one purpose. Correct utilization and interpretation of this study can significantly affect diagnosis and management of seizures, and in turn impact an individual’s quality of life.