An Ambulatory Electroencephalogram (AEEG) is a non-invasive test that records the electrical activity of the brain, or brain waves. Unlike a standard, brief EEG performed in a clinic, the AEEG is a portable system designed for extended monitoring outside of a medical facility. Small, flat metal discs called electrodes are placed on the scalp to detect the tiny electrical signals generated by the brain’s neurons. The AEEG continuously captures brain function, usually spanning 24 to 72 hours, providing a comprehensive view of activity in a patient’s natural environment.
Why Extended Monitoring is Necessary
A standard, in-clinic EEG typically records only a 20 to 40-minute sample of brain activity, which is insufficient for capturing events that occur infrequently. Brain activity constantly fluctuates, and abnormal patterns may only appear sporadically or during specific times, such as while a person is sleeping. If the symptoms being investigated are short-lived or happen only once every few hours, a brief test is likely to miss them.
The AEEG overcomes this limitation by recording for a longer period in the patient’s real-world setting, including during sleep cycles and daily routines. This extended monitoring significantly improves the probability of capturing unpredictable neurological events and transient symptoms. The test is often used when previous short-term EEGs have not provided a clear diagnosis or to evaluate the effectiveness of an existing treatment plan.
Preparing for the At-Home Test
Preparation for the AEEG test begins with careful attention to the hair and scalp to ensure the electrodes adhere properly and the signal quality is high. Patients are instructed to wash their hair thoroughly with only shampoo before the appointment, strictly avoiding the use of conditioners, gels, oils, hairspray, or other styling products that could interfere with electrode contact. Wearing a shirt that buttons or zips down the front is also necessary, as nothing can be pulled over the head once the electrodes are placed.
During the hook-up appointment, which typically takes between 60 and 90 minutes, a technologist measures the head and places numerous small electrodes onto the scalp. These metal discs are secured using a special conductive paste or glue to ensure they remain in place for the entire monitoring duration. The electrodes are then connected by wires to a small, portable recording device, which is usually worn in a pouch, shoulder bag, or on a belt. The technologist provides detailed instructions on the equipment’s operation before the patient leaves for the at-home monitoring period.
Daily Life During Monitoring
While the AEEG allows patients to return to their typical daily environment, certain restrictions are necessary to protect the equipment and preserve recording quality. The most important limitation is the prohibition of showering, bathing, or swimming, as water can damage the electronics and loosen the electrode glue. Patients must also avoid strenuous physical activity that causes excessive sweating, as moisture and movement can create electrical “noise” (artifacts) or cause the electrodes to slip.
Patients are encouraged to maintain a detailed log or diary throughout the monitoring period, noting their activities, meal times, and any symptoms they experience. Most ambulatory devices include an “event button” that the patient or a caregiver should press immediately whenever a suspected event or symptom occurs. Pressing this button places a time-stamp directly onto the EEG recording, allowing the medical team to precisely correlate the patient’s physical experience with the brain’s electrical activity.
Interpreting the Data
Once the monitoring period is complete, the patient returns the portable recorder and the raw data is downloaded. The first step in data analysis involves synchronizing the patient’s written log entries with the time-stamped electrical recordings. This synchronization allows the interpreting physician to assess the brain’s activity during the precise moments the patient reported symptoms or pressed the event button.
The initial review of the data is performed by a trained EEG technologist who scans the hours of recording to identify segments that contain abnormal electrical patterns. The final interpretation is performed by a neurologist specializing in brain activity analysis. The neurologist looks for abnormal wave patterns, such as spikes, sharp waves, or slow waves, and determines if these correlate with the logged symptoms or changes in the patient’s behavior. A detailed report is then prepared, and the patient’s physician discusses the findings and the next steps in treatment or diagnosis.