Summary Of Evidence

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Analysis of Evidence

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Abstract:

An electroencephalogram (EEG) is a diagnostic test that measures the electrical activity of the brain (brainwaves) using highly sensitive recording equipment attached to the scalp by fine electrodes. It is used to diagnose neurological conditions.

EEGs can be recorded by ambulatory cassette. Ambulatory cassette-recorded EEGs offer the ability to record the EEG on a long-term, outpatient basis. Electrodes for at least four (4) recording channels are placed on the patient. The cassette recorder is attached to the patient’s waist or on a shoulder harness. Recorded electrical activity is analyzed by playback through an audio amplifier system and video monitors.

Ambulatory EEG monitoring may facilitate the differential diagnosis between seizures and syncopal attacks, sleep apnea, cardiac arrhythmias or hysterical episodes. The test may also allow the investigator to identify the epileptic nature of some episodic periods of disturbed consciousness, mild confusion, or peculiar behavior, where resting EEG is not conclusive. It may also allow an estimate of seizure frequency, which may at times help to evaluate the effectiveness of a drug and determine its appropriate dosage.

Indications:

• Inconclusive EEGs;
• Experiencing episodic events where epilepsy is suspected but the history, examination, and routine EEG do not resolve the diagnostic uncertainties;
• Patients with confirmed epilepsy who are experiencing suspected non-epileptic events or for classification of seizure type (only ictal recordings can reliably be used to classify seizure type (or types) which is important in selecting appropriate anti-epileptic drug therapy;
• Differentiating between neurological and cardiac related problems;
• Adjusting anti-epileptic medication levels;
• Localizing seizure focus for enhanced patient management;
• Identifying and medicating absence seizures;
• For suspected seizures of sleep disturbances;
• Seizures which are precipitated by naturally occurring cyclic events or environmental stimuli which are not reproducible in the hospital or clinic setting.

Ambulatory monitoring, however, is not necessary to evaluate most seizures, which are usually readily diagnosed by routine EEG studies and history.

Limitations:

• Study of neonates or unattended, non-cooperative patients;
• Localization of seizure focus/foci when the seizure symptoms and/or other EEG recordings indicate the presence of bilateral foci or rapid generalization.