EEG Monitoring

Monitoring is done for many different reasons. Sometimes monitoring is done to try and make sure the seizures are of they type we expect. Other times it is done to make sure the diagnosis of epilepsy is correct, and that there is not some other cause that might explain blackouts. Often inpatient monitoring is done as part of the assessment to see if surgery for epilepsy is possible.

Whatever the reason, it is very important to record a seizure if we can. People often worry that they will have a seizure, but during an EEG, that is what we want to happen, so we can see what type it is and where it originates from. This helps to ensure we are giving the best treatment. 

Video EEG monitoring is an extension of the routine EEG, which you may have already had. Small surface electrodes are glued on the scalp to record the electrical activity of the brain. At the same time as the EEG recording we will be taking a video of you to compare with the EEG. This monitoring is continuous (24 hours a day) for the whole period of your inpatient stay.

Procedure

EEG can be performed on a short- or long-term basis, depending on the patient's particular situation. A typical short-term test takes approximately 90 minutes. During the test, the patient may be asked to hyperventilate and may be shown a strobe light that flashes at different speeds. Both activities can help reveal different brain patterns that are useful for diagnosis. Sometimes, physicians also want to observe brain patterns that occur in sleep. For sleep tests, the patient may be asked to stay awake most of the night prior to the EEG appointment or in some cases may be given a mild sedative.

24-hour ambulatory EEG records brain activity for 24 hours on a small tape recorder that is worn around the waist. Electrodes are applied to the scalp as usual, and the patient's head is typically bandaged to protect the electrode connections. The patient is sent home with a diary to record activities and any symptoms during the 24-hour monitoring period.

Long-term video EEG is an EEG that involves a prolonged recording of the patient's brain activity as well as a video tape recording of the patient's actual behavior during epileptiform (seizure) activity. The patient is usually monitored for several hours, even days, in a specialised epilepsy evaluation and monitoring unit. The patient's anti-epileptic medications are reduced or withdrawn to induce epileptiform seizures. Typically, several seizures may occur each day. In some patients, no seizures may occur for several days, whereas other patients may have more than a dozen seizures per day. The physician reviews the EEG and videotapes recorded before, during, and after each captured seizure to determine the nature of the seizure activity and decide on an appropriate course of treatment.

Recommendation for patients to ensure a quality EEG recording can be obtained:

• Ensure that your hair is clean and dry, and do not use any hair gels, dressings, or hairspray before the test. Dirty hair or scalp can interfere with electrode sensitivity.
• Do not consume sugar, caffeine, alcoholic beverages, or chocolate 12 hours before the test. These substances are stimulants that can affect the accuracy of the EEG recording.
• Take your regular medications, unless instructed otherwise by your doctor, and bring a current list of any seizure or other medications you use.
• Wear comfortable clothing.