The epilepsy monitoring unit (EMU) is a specialized environment for the diagnosis and management of seizures or spells. The availability of continuous video-EEG monitoring in the setting of an EMU has, to a certain extent, revolutionized the care of epilepsy patients.
Unfortunately, this highly specialized diagnostic modality is unknown to many patients and underutilized by many physicians, despite being available for many years. This is, in part, because the service exists primarily at epilepsy centers (referral centers) and some of their satellite campuses.
It should be noted that there are some other settings where continuous video-EEG monitoring can be utilized, for example in an ambulatory outpatient setting and in the intensive care unit.
The focus of this summary will be to highlight the purpose of video-EEG monitoring in the setting of an EMU and, in doing so, to address some common patient concerns and answer some questions about the procedure. In turn, this summary serves to increase awareness about this technologically advanced diagnostic capability for both patients and physicians.
The EMU is a large topic of discussion. Associated with it are issues such as, but not limited to, intracranial monitoring, operational protocols, staffing, interpretation of studies, and potential risks that will not be covered here. The most important principle is that all studies performed in the EMU be done with the underlying goals of quality and safety.
Generally, an EMU study involves a multiple-day stay. It is done on an elective basis in an inpatient unit with video-EEG capability. Patients are admitted to specialized hospital rooms. In many cases family members are permitted to stay. The patient’s ability to move about is somewhat restricted primarily for safety reasons.
The majority of patients admitted for the study have already had a routine EEG. A routine, or “regular,” EEG lasts approximately 20 to 30 minutes and can be done with or without video, on an inpatient or outpatient basis. Many patients with seizures, epilepsy, or spells are initially referred to a neurologist or epileptologist mainly for the purpose of obtaining a routine EEG. The underlying anatomic and electrophysiological principles for an EMU stay with regard to the hookup and setup are the same as a that of a routine EEG.
The key differences are, firstly, that an EMU stay is longer in duration. The exact length is determined by the clinical purpose and, more importantly, by the findings obtained during the study. As such, an EMU stay could be longer or shorter than the estimate initially provided at the time of scheduling. Secondly, the study involves continuous audio and video monitoring, and runs 24 hours a day. There are no breaks in the recording and generally the patient is not allowed to leave the room unless a seizure workup or a medical emergency necessitates it. Leaving the room results in a discontinuity of the recording. Because of the duration and restriction, patients often dislike the study, complaining of boredom and wanting to leave early.
In most cases, the major goal of a video-EEG monitoring study is to capture and record seizures and/or the patient’s typical events per history. This is the key to its diagnostic capability.
A significant portion of routine EEGs are normal in epilepsy patients but this does not necessarily rule out the diagnosis of epilepsy. By virtue of longer recording time, and hence increased sample size, the EMU study is much more sensitive at not only capturing seizures but also recording interictal epileptiform activity. Because of this, an EMU study can provide confirmation of an epilepsy diagnosis if needed.
The very nature of video-EEG monitoring causes patient and family anxiety. Frequently the greatest concern is the capturing of seizures and epileptic events rather than preventing them. As in all areas of medicine, there is a balance between risk and benefit. With regard to the EMU, the risk is the potential for injury associated with such a stay; the benefit is the diagnostic information gained and its subsequent utilization for treatment.
Since the major purpose of an EMU stay is to record the patient’s episodes, it is imperative that the ordering physician explain to the patient and his or her family the goals, limitations, and potential dangers of the stay. That explanation should include the procedures and protocols put in place to keep the patient safe.
The EMU’s Role in the Medical Work-Up
Most commonly the EMU is utilized to characterize the type of epileptic seizures a patient is experiencing. The correlation between the clinical (observed) and electrical (EEG) aspects of a seizure helps guide treatment by assisting in the choice of medication. Other purposes include localization, determining the area of seizure onset. This information is essential in determining the appropriateness of surgery as a treatment option and pre-surgical evaluation. Other uses of EMU recordings include determining the frequency of seizures and, in turn, using this as a basis for medication adjustments. In some cases the frequency of seizures is higher than that reported because subclinical (electrographic) seizures are captured that the patient did not even know were occurring. Another purpose is to gauge response to anti-epileptic drug (AED) therapy, and, if needed, make therapy adjustments.