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