EEG Monitoring
Video-EEG monitoring is critical to determining if surgery could be an effective treatment for those whose seizures are not controlled with medical therapy.
The Epilepsy Monitoring Unit (EMU) at UC San Diego Health Epilepsy Center is a state-of-the-art seizure evaluation center.
At the EMU, patients’ seizures are evaluated through continuous video and EEG recording in a hospital setting. We do this to determine the type of seizure, site of onset, and frequency of seizures.
Specifically, the EMU enables us to analyze the electrical and behavioral components of each seizure in order to verify a patient’s diagnosis and improve his or her treatment plan.
Every evaluation is tailored to the patient’s individual history. We often try to record 3 to 5 seizure examples to determine their type and location. The seizures are evaluated in a hospital setting under conditions of maximal patient safety.
We are interested in recording natural seizures; we do not give agents to induce seizures. Most patients respond to a gentle tapering of their regular seizure medications combined with sleep reduction.
How EEG Monitoring Works
Noninvasive EEG electrodes are applied to the scalp and an IV is started to allow for quick treatment if necessary. Patients are recorded day and night with a continuous video camera, except when in the bathroom, in order to analyze any seizure activity. In addition, patients are not permitted to leave the Epilepsy Monitoring Unit (EMU) during the evaluation except for emergencies.
Because of tapering medication and sleep reduction, seizures may be more frequent or stronger than usual. A special team of professionals works closely with patients during their stay in the EMU and the hospital setting provides for maximal patient safety. If seizures become too long, strong or frequent, medication is given via IV to treat seizures quickly.
The average length of hospitalization in the EMU is 3-5 days, but many patients are asked to stay longer to record a good sample of seizures.
We encourage patients to have a friend or family member with them in the EMU to keep them company and to help identify events that could be seizures. A trained technician or nurse is present at all times to observe the patient on closed-circuit video.
As soon as a seizure is observed to start, the patient, the companion or the seizure technician may press an alarm to signal nursing staff to come to assess and assist the patient. Epileptologists review the EEG daily to look for “silent” seizures that may have gone unnoticed during the prior 24 hours, including sleep.
Referring physicians will receive a report of the detailed findings from the video-EEG monitoring.
EEG Monitoring for Epilepsy
Phase II Video-EEG Monitoring
Phase II Video-EEG Monitoring with Minimally Invasive Electrodes
When noninvasive scalp electrodes do not identify the seizure focus with enough detail, phase 2 video-EEG studies may be recommended. One type of phase II video-EEG involves the placement of foramen ovale electrodes (FOE). These electrodes are named after a natural hole in the skull base through which our epilepsy surgeons place them. They are considered minimally invasive because the surgeon does not need to make any opening in the skull to insert the electrodes.
UC San Diego epilepsy surgeons have one of the largest experiences in the United States in placing foramen ovale electrodes. FOEs do not pierce the brain, but lie next to important structures like the hippocampus. EEG data from these electrodes provide far greater detail compared to scalp recordings in identifying EEG signals from certain types of temporal lobe seizures.
After placement of FOEs, the patient is transferred to the EMU where noninvasive scalp electrodes are also placed, and the video-EEG monitoring begins.
Phase II Video-EEG Monitoring with Stereo-EEG, Subdural Strips, Grids and Other Electrodes
When necessary, there are other types of electrodes that can be placed inside the skull or even inside the brain to record seizures. Most of these require the surgeon to create an opening in the skull to place the electrodes around the suspected seizure focus.
Under anesthesia, these sterile electrodes are placed on the surface of the brain, or carefully directed within the brain structure of interest. After recovery from anesthesia, the patient is transferred to the EMU for further video-EEG monitoring to capture seizures for “high definition” analysis.
This allows doctors to fine-tune the information about where the seizures arise. The implanted electrodes can also be used to “map” the brain areas around the seizure focus to identify areas important for speech, movement and sensation.
This type of surgery is almost always reserved for patients who are in the final stages of presurgical evaluation and are expected to have brain surgery to treat their epilepsy. These procedures are not experimental and are routinely done in most comprehensive Epilepsy Centers in the United States and around the world.