|By Adrian Sparrow
The brain is constantly sending and receiving electrical signals. When that signaling gets disrupted, a seizure occurs. Abnormal electrical activity in the brain doesn’t always occur during a routine EEG, especially when the patient only experiences epilepsy waves once every few hours or during certain times of the day. A routine EEG in an office only takes a 20-40 minute sample of brain activity, or just 2% of a single day.
An ambulatory EEG test measures neurological activity across several hours or days to provide more comprehensive results. Patients are more relaxed in their homes, leading to more accurate EEG results, so some ambulatory EEGs are performed at home rather than in an epilepsy monitoring unit (EMU). This way, the EEG can record brain waves while the patient goes through their normal routine, including sleeping, and ideally will detect not just one seizure but additional seizures after the first event to provide a clearer picture for the neurologist.
During the test, the patient wears EEG nodes on their scalp that are attached to a recording device. Most of these devices have an ‘event’ button that marks the time on the EEG recording when pressed by the patient or caregiver. This way, doctors can compare the event with other factors like what the patient was doing at the time or what they felt versus what caregivers or the test’s video recording saw.
The length of time for such a test is an important factor to consider- how long should the test last to get the most accurate results for diagnostic purposes?
One study suggests that an ambulatory EEG at home should last at least 48 hours for children and 48 to 72 hours for adults.
Across the study of more than 3500 unique cases, researchers discovered that more than half the patients had their first event within 12 hours of beginning the test. The patients in the study had a wide range of recorded durations. The shortest test was just over two hours, and the longest was more than 165 hours, or three hours shy of seven days.
By comparing the times and number of events across all the patient reports, researchers found that the first event occurred within 48 hours of beginning the test for over 90% of patients. Children had 95% of events recorded by hour 48. Adults only had 82% at the same timestamp, and 97% of events were recorded by hour 72.
Every patient has different needs that doctors consider when prescribing an ambulatory EEG. Some tests may take less than 24 hours or more than 72 hours. Ultimately, the length of the test is determined by your individual needs and what your insurance allows.