Video-electroencephalography (EEG) studies are created by simultaneously recording the patient's EEG and video image with sound. These are time-locked and combined for later review. The result is a powerful methodology for the clinical diagnosis and management of paroxysmal disorders. This chapter will focus on clinical motivation and technology underlying the combining of audio and video information with the EEG.
Clinical Utility Of Video-EEG
One of the most difficult symptoms to evaluate, whether in the emergency department or the neurologist's office, is an episode of loss of consciousness. This complaint accounts for up to 3% of visits to emergency rooms and 1% of admissions to hospitals.1 The differential diagnosis of an episode of loss of consciousness is very long and includes cardiogenic, neurologic, and psychiatric illnesses. Although epilepsy is characterized by recurrent, highly stereotyped episodes of transient neurologic dysfunction, it is often difficult to distinguish from nonepileptic disorders based on routine evaluation alone. Paroxysmal movement disorders and sleep disorders are often mistaken for seizures. Transient alterations in cerebral blood flow and oxygenation, such as those that occur during a transient ischemic attack, orthostasis, syncope,2 or migraine, may cause recurrent events that resemble epilepsy. Integral to the process of narrowing this complex differential is the EEG. By combining the EEG with time-locked video information, the value of this tool is greatly enhanced.
Localization of seizure onsets is important for several reasons. First, identification of partial seizures may direct specific treatments. For instance, if a person's partial seizures are refractory to medical management, surgery may be considered. For surgery to be successful, accurate identification of the region of seizure onset is needed.3
Seizure semiology, or description of the clinical appearance of an event, is a critical component of both diagnosis and localization. Of course, some brain regions are “silent.” That is, a seizure may start in one area but produce no obvious outward signs or symptomatic complaints. When the seizure spreads to the “symptomatic” cortex, localizing information becomes available.4
It can be very difficult, however, to reconstruct a person's seizure semiology from the history alone. Because an epileptic seizure can affect a person's thinking and memory, the patient may not have sufficient recall of events.5 Although descriptions obtained from witnesses may be helpful, most family members do not accurately recall the details of the events.6,7 They may have been too frightened or may not have known what signs were important to record. If events are infrequent, it may simply have been too long since the last event to accurately remember the details. In short, witnesses' accounts of seizures are often incomplete or inaccurate.
Video recording of a patient's habitual events can provide the clinician with a complete picture of the semiology. However, after viewing a seizure either in person or on video, even experienced epileptologists find it difficult ...