Epilepsy is among the most common serious disorders of the brain, ranking with depression and other affective disorders, Alzheimer disease and other dementias, and substance abuse. According to the World Health Organization, the global burden of disease represented by epilepsy is equivalent to lung cancer in men and breast cancer in women. Epilepsy is a treatable condition; however, in the United States and other industrialized countries, 80% of the cost of epilepsy is due to patients whose seizures are not controlled by antiepileptic drugs (AEDs). Assuming that the appropriate medications are prescribed at therapeutic doses and that patients take their medications correctly, failure to achieve seizure control can mean that the ictal events are not epileptic, the seizure type and epilepsy syndrome diagnoses are incorrect, or the AEDs are ineffective. Video-electroencephalographic monitoring (VEM) is the diagnostic test of choice to determine whether the uncontrolled events are epileptic and if so, to correctly classify the seizure type and epilepsy syndrome. In the situation where AEDs are ineffective, VEM is indicated to determine whether the patient might be a candidate for surgical treatment, which, in carefully chosen patients, is highly likely to result in complete freedom from disabling seizures. Given that 30 to 40% of patients in the United States and other industrialized countries continue to have seizures despite presumably appropriate pharmacotherapy, there is a tremendous need for VEM services. Although there has been a considerable increase in the establishment of such facilities in the United States, clearly only a small percentage of the ∼1 million patients in this country who continue to have seizures despite AED treatment have had access to VEM. With current, and anticipated future, increases in VEM availability, the Atlas of Video-EEG Monitoring is sorely needed.
EEG telemetry for epilepsy originated in the early 1960s at the University of California, Los Angeles (UCLA), after Paul Crandall pioneered the stereotactic implantation of chronic intracerebral depth electrodes to localize the epileptogenic region for surgical resection. Although the stereotactic depth electrode procedure was devised by Jean Talairach and Jean Bancaud in Paris, regulations in France did not allow the electrodes to remain in place for more than a few hours. Consequently, ictal recordings were obtained by inducing seizures using electrical stimulation or convulsant drugs, such a pentylenetetrazole. Because no such regulations existed in California, Crandall adapted the Paris technique and carried out long-term chronic inpatient recordings to capture spontaneous seizures. At the same time, Ross Adey, a neuroscientist at the UCLA Brain Research Institute, was developing EEG radio telemetry for the National Aeronautics and Space Administration (NASA) to record continuous EEG from chimpanzees orbiting the earth in space capsules. Crandall immediately realized that this technology would be useful for continuous inpatient EEG recording, and his electronics technician, Anthony Dymond, built the first inpatient epilepsy telemetry system with a radio telemetry device. Dymond then commercialized his telemetry equipment. At that time, recording ictal events on routine EEG was extremely difficult because filters were not sufficiently advanced to eliminate movement and muscle artifact. The radio telemetry had no wires, and muscle activity did not contaminate tracings from the depths, so ictal recordings in this situation were extremely clean. Over the next 2 decades, at several centers, simultaneous video monitoring was introduced, and EEG telemetry evolved into hard-wired monitoring with improvements in filters, allowing recordings to also include scalp and sphenoidal electrodes. Although VEM was initially used for presurgical evaluation, once it was no longer considered experimental, differential diagnosis became another important application. However, VEM remained essentially limited to major academic centers.
With the advent of digital EEG, then digital video, there has been an explosion of VEM facilities in the past decade or so, most of which are not in academic epilepsy centers. Although this expanded service is still not sufficient to meet the current need, there is a danger that application of technology will outstrip appropriate utilization. There are, as yet, no official standards for establishment of VEM facilities, nor does the special certification for clinical neurophysiology of the American Board of Psychiatry and Neurology have a category for interpreting ictal video-EEG recordings, which requires a different skill set from reading routine EEGs. Over the same period, there has been a considerable increase in hospitalizations for epilepsy, many presumably for inpatient VEM. Interestingly there is no evidence of a change in surgical procedures performed for epilepsy, which could mean that most of the increase in VEM has been for differential diagnosis, although there is the possibility that potential surgical candidates monitored outside academic centers are not being referred to surgical programs. Detailed VEM instruction is required to ensure not only that differential diagnosis is managed correctly, but also that potential surgical candidates are recognized and referred to epilepsy surgery centers in a timely manner. Surgical treatment for epilepsy remains underutilized. The Atlas will meet these instructional needs and it is hoped increase appropriate epilepsy surgery referrals.
VEM has evolved from a highly selective procedure practiced at only a few major medical centers to a much more commonly performed service. It is a cost-effective approach to solving major diagnostic questions in epileptology, and patients would greatly benefit if VEM becomes routinely available in the future. However, given the small number of training programs available for VEM and presurgical evaluation, there is an urgent need for alternative instructional materials to meet the increasing demand for this service. This Atlas goes a long way to resolving the knowledge gap.
Jerome Engel, Jr.
Los Angeles, California