Long-term video-electroencephalography (EEG) monitoring is a diagnostic technique commonly used in patients with epilepsy. It involves the long-term hospitalization of the patient, typically for days or weeks, during which brain waves are recorded via EEG and physical actions are continuously monitored by video. In epileptic patients, this technique is typically used to capture brain activity during seizures. The information gathered can be used for initial prognosis or long-term care management.
History
Like standard EEG-testing, long-term video-EEG monitoring techniques developed from techniques in 1875 by Richard Caton in Liverpool. In 1890, his work was expanded upon by Adolf Beck as developments to the technique were enhanced through animal studies of rhythmic oscillations in the brain due to light stimuli. In these studies, electrodes were placed directly on the surface of the brain. Additional developments made using animal subjects persisted through the early 1900s including the work of Vladimir Vladimirovich Pravdich-Neminsky in 1912, Napoleon Cybulski and Jelenska-Macieszyna in 1914, as well as by Hans Berger in 1924 with the first human EEG recording. These developments lead to the modern EEG techniques which allow for non-invasive measurements using externally placed EEG caps and were established by William Grey Walter in the 1950s. From these easy uses and techniques, a longer-term method of EEG monitoring was developed called long-term video-EEG monitoring which applies these same brain-wave monitoring techniques in a long-duration test format. This test format allows at-home or extended monitoring in clinics and hospitals where the standard EEG monitoring was previously unable to be used. In either case, these EEG measuring techniques allow one to non-invasively measure action potentials of groups of neurons within the brain using transducers called electrodes. The electrical signals from these electrode transducers are then amplified using differential amplifiers to measure potential differences from one area of the scalp or brain to another. The acquired analog signal is then converted to a digital signal to allow processing and storage of the data using an analog-to-digital converter which is then filtered to remove any signal noise not associated with the neuronal activity. The final signal can then be displayed on an external computer screen as a visual representation of the EEG signals measured. Other EEG techniques can sum these cellular responses either temporally or spatially and help determine which areas of the brain are active during specific activities or due to specific stimuli.
Medical Uses
Long-term video-EEG monitoring is utilized in the localization of epileptogenic zones which are the areas of the cortex of the brain responsible for epileptic seizures. Long-term video-EEG monitoring is similar to EEG in that the brain waves are periodically monitored and analyzed by a neurologist, typically one trained in clinical neurophysiology. The neurologist determines when the monitoring is finished and issues the final report after the compiled data is interpreted. The results from the EEG and video monitoring are used to characterize episodic disruptions in brain function and its physical manifestations; many recordings show symptoms of epileptic seizures over time and how severe/frequent the seizures become over a given period of time. The purposes of long-term video-EEG monitoring include discovering where in the brain seizures begin for a given patient, the severity of the seizures (measured according to a scaled order), determining the frequency of the seizures, the duration and prominence of physical activity during the seizure (which may be indicator of status epilepticus, prolonged seizures or increased frequency of seizures without a return to an otherwise normal state), and distinguishing epileptic seizures from psychogenic non-epileptic seizures. Additionally, audio recordings of patients (verbal and nonverbal) may be taken of the subject during those seizures. Each of these topics may then be used to evaluate a subject's candidacy for surgery to treat epilepsy. In adults, long-term EEG monitoring typically involves one of three procedures which include long-term video-EEG monitoring, sleep-deprived EEG monitoring, and 24-hour ambulatory monitoring. Long-term video-EEG monitoring typically lasts from a few hours to several days. Depending on the needs of the patient where sleep-deprived and ambulatory EEG monitoring are often used to further investigate symptoms of epilepsy when a standard EEG reading returns inconclusive results. Furthermore, sometimes all three procedures of long-term EEG monitoring are utilized for a single patient due to niche results found in each. Video-EEG (LTVER) specializes in recording of seizures for topographic diagnosis as well as for diagnosis of paroxysmal clinical events. Sleep-deprived EEG monitoring diagnoses specific EEG abnormalities for syndromic classification. Lastly, Ambulatory EEG focuses on monitoring/ quantification of EEG abnormalities. Long-term video-EEG monitoring is typically used in cases of drug-resistant epilepsy to examine symptoms before surgery and is also used to more precisely diagnose a patient when episodes become more frequent.
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