Summary Of Evidence

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Analysis of Evidence

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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.

This Local Coverage Determination (LCD) addresses EEG testing via 24 hour ambulatory recording.

Ambulatory EEG monitoring is a diagnostic procedure for patients, in whom a seizure diathesis is suspected but not defined by history, physical or resting EEG. Twenty-four hour ambulatory recorded EEGs offer the ability to record the EEG on a long-term, outpatient basis. Recorded electrical activity is analyzed by playback through an audio system and/or 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 routine “resting” EEGs
• Experiencing episodic events where epilepsy is suspected but the history, examination, and routine EEG recordings 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(s)), which is important in selecting appropriate anti-epileptic drug therapy
• Differentiating between neurological, cardiac, and psychiatric related problems
• 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. Medicare anticipates that many of these outpatient studies will not provide the diagnosis within the first 24 hours, but expects that 48 hours of monitoring will be diagnostic in most circumstances. Ambulatory monitoring beyond 48 hours frequently produces poor data in the period after 48 hours, as electrode contact may no longer be optimal after 48 hours. Occasionally, patients may require an additional 48 hour monitoring period to establish a diagnosis, which is usually performed at a later date. Medical necessity must be documented for review in these circumstances. This 48 hour limitation does not apply to the inpatient setting where patients are frequently withdrawn from their anti-epileptic regimens, and where precise pre-surgical localization of epileptic foci is often conducted.

It is anticipated that once the diagnosis has been established, this study will not be repeated for the same diagnosis, nor will it be used in the monitoring of a therapeutic regimen. Again, this expectation will not be applied to patients readmitted for inpatient care of their seizure disorder.

LIMITATIONS (NON-COVERED INDICATIONS):

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