Clinical UM Guideline

This document addresses electroencephalography (EEG) with or without video monitoring in outpatient settings. Outpatient settings may include, but are not limited to, a hospital’s ambulatory (same day) department, a physician’s office, outpatient clinic, or in the member’s home.

Note: This document does not address attended video EEG monitoring performed in an inpatient hospital setting. For criteria related to attended video EEG monitoring in an inpatient setting, refer to the applicable guidelines used by the plan.

Note: For a high-level overview of this document, please see “Summary for Members and Families” below.

Medically Necessary:

Ambulatory EEG with or without video monitoring is considered medically necessary for any of the following indications:

1. To diagnose a seizure disorder when either the clinical history or examination is suggestive of epilepsy, but routine EEG is non-diagnostic; or
2. To classify seizure type in individuals with epilepsy after a routine EEG is non-diagnostic and classification will be used to select drug therapy; or
3. To differentiate between paroxysmal non-epileptic events and seizures; or
4. To document seizures precipitated by naturally occurring cyclic events or extraneous stimuli (for example, flashing lights, loud sounds, sudden movements) that are not reproducible in the hospital or laboratory setting; or
5. To evaluate seizures or syncope suspected to be cardiogenic in etiology when cardiac evaluation has not been diagnostic; or
6. To quantify the number of electrical seizures in individuals who experience frequent seizures.

Not Medically Necessary:

Ambulatory EEG with or without video monitoring is considered not medically necessary when the above criteria are not met.

This document describes clinical studies and expert recommendations, and explains when ambulatory electroencephalography (EEG) is clinically appropriate. The following summary does not replace the medical necessity criteria or other information in this document. The summary may not contain all of the relevant criteria or information. This summary is not medical advice. Please check with your healthcare provider for any advice about your health.

Key Information

An electroencephalogram, or EEG, is a test that records the brain’s electrical activity. Ambulatory EEG is done outside the hospital, such as in a clinic, doctor’s office, or at home. It may be done with or without video. Video can help match body movements or other events with the brain activity seen on the EEG. This test may help when a routine EEG does not give enough information, but the person’s symptoms or exam suggest epilepsy or another seizure problem. EEG does not send electricity into the body. It records brain activity. Possible drawbacks include skin irritation from the electrodes, missed events if symptoms do not happen during the test, or unclear results that may need more testing.

What the Studies Show

Studies show that ambulatory EEG can find some seizure-related brain activity that routine EEG may miss. This is because ambulatory EEG records brain activity for a longer amount of time, often during normal daily activity and sleep. Studies have also shown that ambulatory EEG may help tell the difference between seizures and events that look like seizures but are not caused by abnormal brain activity.

Some studies found that ambulatory EEG had a higher chance of finding seizure-related activity than routine EEG. Some studies also found that adding video may help doctors understand what is happening during an event. However, ambulatory EEG may still miss events, and some results may be unclear. Better studies are needed to know how often ambulatory EEG changes care in all settings.

When is Ambulatory EEG Clinically Appropriate?

Ambulatory EEG, with or without video, may be appropriate in these situations:

• A seizure disorder is suspected based on the person’s health history or exam, but a routine EEG did not give a clear answer; or
• The person has epilepsy, a routine EEG did not give a clear answer, and classifying the seizure type will help choose drug treatment; or
• The test is needed to tell the difference between seizures and sudden events that are not epileptic seizures; or
• The test is needed to record seizures caused by natural cycles or outside triggers, such as flashing lights, loud sounds, or sudden movements, that cannot be repeated in a hospital or lab; or
• The person has seizures or fainting that may be caused by a heart problem, and heart testing has not given a clear answer; or
• The person has frequent seizures, and the test is needed to count how many electrical seizures are happening.

When is this not Clinically Appropriate?

Ambulatory EEG, with or without video, is not clinically appropriate when the situations listed above are not met. In these cases, the test has not been shown to improve health. Studies support its use mainly when routine EEG has not given a clear answer, when seizure type needs to be clarified, or when certain events need to be recorded. Unnecessary or unproven tests can lead to treatment that does not help.

Return to Description

The following codes for treatments and procedures applicable to this guideline are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services may be Medically Necessary when criteria are met:

When services are Not Medically Necessary:
For the procedure codes listed above when criteria are not met or for all other diagnoses not listed.

Summary

Ambulatory electroencephalography (EEG) provides prolonged recording of brain electrical activity in outpatient settings and has a higher diagnostic yield than routine EEG because it captures brain activity over extended periods, including sleep and routine daily activities. The evidence consistently supports its use as a second-line diagnostic study when routine EEG has not adequately answered an important clinical question.

The strongest evidence supports the use of ambulatory EEG in individuals with suspected epilepsy whose routine EEG is nondiagnostic. Prospective and retrospective studies have consistently demonstrated substantially higher detection rates of interictal epileptiform discharges (IEDs) and electrographic seizures than routine EEG, improving diagnostic confidence when clinical suspicion for epilepsy remains high despite an inconclusive initial evaluation. Recent studies continue to demonstrate higher detection of epileptiform abnormalities and seizures with ambulatory EEG compared with routine EEG.

Ambulatory EEG is also useful for classifying seizure type when routine EEG has not adequately characterized epilepsy. Prolonged recording increases the likelihood of capturing ictal or interictal abnormalities that distinguish focal from generalized epilepsy, information that directly influences selection of appropriate antiseizure medication. Although evidence demonstrating improved clinical outcomes is limited, this application is well supported by clinical experience and professional practice standards.

Evidence also supports ambulatory EEG for distinguishing epileptic seizures from paroxysmal nonepileptic events. Studies have shown that prolonged recording, particularly when combined with video, frequently captures habitual events and can demonstrate whether symptoms occur with or without an electrographic correlate. However, because some epileptic seizures may have minimal or obscured scalp EEG changes, ambulatory EEG should be viewed as an important diagnostic tool rather than a definitive exclusion test for epilepsy. Inpatient video EEG remains the diagnostic standard when psychogenic nonepileptic seizures require definitive confirmation.

The ability to monitor individuals in their normal environment also supports ambulatory EEG for documenting seizures precipitated by naturally occurring cyclic events or environmental stimuli that cannot be reliably reproduced during a routine outpatient study. Prolonged recording increases the likelihood of capturing infrequent or situational events that might otherwise be missed during a brief laboratory evaluation.

Ambulatory EEG may also assist in the evaluation of recurrent seizures or syncope when a cardiac cause remains a consideration after nondiagnostic cardiac evaluation. Although the supporting evidence is limited and largely observational, prolonged EEG with simultaneous electrocardiogram (ECG) capability may help distinguish neurological from cardiogenic causes in carefully selected individuals whose diagnosis remains uncertain after appropriate cardiac assessment.

Finally, ambulatory EEG is useful for quantifying electrographic seizure burden in individuals who experience frequent seizures. Multiple studies have demonstrated that ambulatory EEG can identify clinically unrecognized seizures and provide a more objective assessment of seizure frequency than member reporting alone. This information may assist with treatment decisions, particularly in individuals who are unaware of some seizure events or whose seizure frequency is uncertain. Recent retrospective data suggest ambulatory EEG may also contribute to decisions regarding antiseizure medication withdrawal by identifying unrecognized seizures or persistent epileptiform abnormalities, although current evidence is insufficient to support a separate indication for medication withdrawal alone.

Overall, the available evidence supports ambulatory EEG as a medically necessary diagnostic test when prolonged outpatient monitoring is expected to provide clinically meaningful information beyond that obtained from routine EEG. The evidence is strongest for evaluation of suspected epilepsy after a nondiagnostic routine EEG, seizure classification, differentiation of epileptic and nonepileptic events, documentation of infrequent or environmentally triggered events, and objective quantification of seizure burden.

Evidence remains insufficient to support expansion of coverage to emerging technologies such as implanted continuous EEG systems or single-channel in-ear EEG devices, or to support ambulatory EEG solely for routine antiseizure medication withdrawal planning.

Discussion

According to the Epilepsy Foundation, epilepsy affects approximately 3.4 million people in the United States. Epileptic seizures can be related to a brain injury or genetics, but the cause is unknown for many individuals with epilepsy. The Centers for Disease Control and Prevention (CDC) estimates epilepsy affects about 456,000 children. The onset rate increases with aging, particularly if an older adult experiences a stroke or develops a brain tumor or Alzheimer disease, all of which may result in seizures or epilepsy. Some reports indicate that more than 570,000 adults over the age of 65 suffer from the disorder. The Epilepsy Therapy Project notes that 10% of the population will have a seizure in their lifetime. In addition, it is estimated that over one-third of individuals have epilepsy with drug-resistant seizures (seizures that do not respond to treatment).

An EEG test records continuous and prolonged electrical activity of the brain to assist in the evaluation and diagnosis of seizure disorders, epilepsy syndromes, and other conditions.

Ambulatory EEG monitoring in the outpatient setting (for example, a home environment) is a diagnostic test used to evaluate an individual in whom a seizure disorder is suspected but undefined by the person’s medical history, physical examination, or a routine (standard/resting) EEG. Ambulatory EEG allows for prolonged monitoring outside a hospital or clinic setting. Ambulatory EEG recordings are utilized in the evaluation and differential diagnosis of other conditions including cardiac arrhythmias, psychogenic episodes, sleep apnea, syncopal episodes, and transient ischemic attacks if these episodes are not identified by conventional studies. In most instances, a routine EEG performed at a clinic or outpatient epilepsy facility can identify brain activity specific to seizures; however, when routine EEG is inconclusive and the clinical history strongly suggests seizure activity, an ambulatory EEG may be indicated. Routine EEGs and ambulatory EEGs may not capture all the suspected events. In these instances, it may be necessary to add video to the EEG. There have been technologic developments for EEG which include the use of continuous EEG and synchronized video recording in the home or ambulatory setting. The technology is performed to supplement descriptions of seizure activity by care takers. A video EEG records brainwave activity on an EEG and a video of what is going on at the same time. The purpose of this is to compare what is happening when a seizure or event occurs and compare the video to what the EEG records at the same time.

Ambulatory EEG testing provides a continuous recording of the brain’s electrical activity that can range from several hours to several days (typically 48 hours to 72 hours). In the outpatient setting (physician office, clinic, or in the home setting), a set of electrodes with leads is secured to the person’s scalp and a recording unit is attached by a belt to the waist or on a shoulder harness. The technology has evolved such that portable recordings of up to 32 channels can record computer-assisted spike and seizure detection rates over several days. The computer software is designed with the goal to increase the chance of recording an ictal event or interictal (the period of time between seizures) epileptiform discharges (IEDs) during the person’s routine daily activities and sleep. The person being monitored and observers (family member, caregiver) have the opportunity to “tag” portions of the recording during clinical events using a push-button device. Some systems can be configured for polysomnography, with inputs available for monitoring simultaneous electrocardiogram (ECG), oximetry, pulse, respiratory, synchronous video recording, and other parameters. The gold standard for evaluating the large amount of data collected by a computer-assisted system is visual analysis at the end of the testing period by a highly trained individual (Foley, 2000; Seneviratne, 2013; Waterhouse, 2003). For safety reasons, sleep deprivation, tapering of anti-seizure medication and hyperventilation are usually not done during ambulatory EEG (Tatum, 2023).

Seizures vary to such an extent that epilepsy specialists frequently re-classify seizure types. Current classifications include three basic categories: generalized onset seizures, focal onset seizures, and unknown onset. Classifying the type of seizure assists the physician in diagnosing whether or not an individual has epilepsy or another condition and is important in the selection of appropriate anti-epileptic drug treatment. Generalized onset seizures are produced by electrical impulses throughout the entire brain. These seizures affect both sides of the brain at the same time. The most common types of generalized seizures include absence seizures (petit mal), atonic seizures, clonic seizures, generalized tonic-clonic (grand mal), myoclonic seizures, and tonic seizures. In focal onset seizures, the electrical impulses can start in one area on one side of the brain. When an individual is awake and aware during a seizure this is known as a focal aware seizure. Conversely, if an individual is confused or they have impaired awareness during their seizure this is referred to as focal impaired awareness. An unknown onset seizure is when the beginning of the seizure is not known. This may be because the seizure is not witnessed. Seizure syndromes are specific to adults and children of all ages. Epilepsy syndromes in adults include, but are not limited to temporal lobe epilepsy, primary generalized epilepsy, idiopathic focal epilepsy, and progressive myoclonic epilepsy. Epilepsy syndromes in children include, but are not limited to febrile seizures, Landau-Kleffner Syndrome, Lennox-Gastaut Syndrome, and benign occipital epilepsy.

Clinical events known as psychogenic non-epileptic seizures (PNES) are non-epileptic seizures where the person perceives altered movement, emotion, sensation, or an experience similar to those involved with epilepsy. These events are without an EEG documented ictal association. PNES occur in as many as 20% of persons evaluated at inpatient epilepsy monitoring centers and in 5% to 20% of outpatient populations. Both PNES and epileptic seizures are concurrent in an estimated 10% to 60% of individuals with epilepsy (Waterhouse, 2003). In a retrospective review conducted by Morris and colleagues (1994), 36% (125 of 344) of participants in an outpatient study of ambulatory EEG activated the ambulatory event marker for events that were not associated with EEG changes. However, since some seizures are associated with minimal EEG changes or with movement and muscle artifacts that obscure the EEG, an ambulatory EEG is considered clinically appropriate as the initial screening procedure for non-epileptic events. Inpatient video EEG remains the gold standard to definitively diagnose non-epileptic PNES (LaFrance, 2013; Waterhouse, 2003).

Routine EEG in persons with epilepsy may fail to demonstrate interictal epileptiform activity. Ambulatory EEG is useful in documenting interictal epileptiform activity when routine EEG is non-diagnostic due to the extended sampling period. In those with daily to almost daily seizures, ambulatory EEG with video may be able to capture events. Studies looking at the diagnostic yield of ambulatory EEG indicate that 6% to 15% of ambulatory EEG recordings identify seizures (Waterhouse, 2003). Morris and colleagues (1994) retrospectively studied the ambulatory EEG results of 344 individuals referred to a community-based outpatient EEG service for further diagnostic evaluation using a 16-channel bipolar recording system. Ambulatory EEG was reviewed for the presence of user-identified events, computer identified interictal and ictal abnormalities, and periodic time samples. A push-button recording that signified a clinical event was obtained in 166 individuals (48.3%); 41 (11.9%) of these recordings included a seizure and 125 (36.3%) showed no EEG changes during the habitual event. An EEG abnormality was identified by the computer in an additional 90 recordings (26.2%), for an overall clinical usefulness of 74.4%. Among the 191 individuals referred with previously normal routine EEGs, 129 (67.5%) of these recordings were useful; 48 (25.1%) of these tracings were abnormal and an additional 81 push-button events (42.4%) showed no changes were recorded from background EEG. Tatum and colleagues (2001) retrospectively studied 502 participants evaluated with a computer-assisted 16-channel ambulatory EEG, identifying that 38.3% of seizures went unreported by participants with 8.5% demonstrating seizure activity during the recording period (mean=28.5 hours). Faulkner and colleagues (2012a) studied the value of outpatient ambulatory EEG in the diagnosis and classification of epilepsy. When compared to routine EEG, ambulatory EEG demonstrated a higher yield and diagnostic sensitivity.

In a 2023 study by Hernandez-Ronquillo and colleagues, the authors evaluated the diagnostic accuracy of ambulatory EEG compared to routine EEG and repeat/second routine EEG at capturing IED/ seizures in individuals with patients with a first single unprovoked seizure (FSUS). There were 100 individuals who underwent a first routine EEG, a second routine EEG, and an ambulatory EEG. A total of 54% of individuals were diagnosed with epilepsy. The sensitivity of the first routine EEG at identifying IED/seizures was 11%, the second routine EEG was 22%, and the ambulatory EEG was 72%. Specificity was not statistically different between the three EEG modalities; first routine EEG was 98%, second routine EEG was 100%, and ambulatory EEG was 98%. Positive predictive value (PPV) for the first routine EEG was 100%, 92% for the second routine EEG, and 97% for the ambulatory EEG. Negative predictive value (NPV) was 49% for the first routine EEG, 52% for the second routine EEG, and 75% for the ambulatory EEG. The area under the curve (AUC) for detecting IED/seizure for those with a clinical diagnosis of epilepsy was 0.56 (95% Confidence Interval [CI], 0.44, 0.67) for the first routine EEG, 0.60 (95% CI, 0.49, 0.71) for the second routine EEG, and 0.85 (95% CI, 0.77, 0.93) for the ambulatory EEG. The authors note further studies are needed to evaluate the accuracy of ambulatory EEG to capture IED/seizures in those individuals presenting with FSUS.

In a 2016 retrospective review by Lawley and colleagues, review of 88 ambulatory video EEG studies was completed in order to assess the diagnostic utility. Clinical events (defined in this study as epileptic seizures, physiologic non-epileptic events, or PNES) occurred during 55 of the ambulatory video EEG studies (62.5%). In 26 of these, at least one event was also clearly seen on video recording. In 6 of the ambulatory video EEG studies which captured events, a diagnosis of epileptic seizures was confirmed. The remaining 49 studies which captured events had no associated changes in the underlying ambulatory video EEG. The authors noted an overall diagnostic utility of 67%. Results of ambulatory video EEG influenced medical management in 34 cases, including change in antiepileptic medication or adoption of an alternate management strategy when a different diagnosis was suggested. Management strategy was changed in 75.0% of cases where an event occurred but was not seen on video. Two studies were unsuccessful because of technical equipment problems (failure to activate the camcorder). And while this study has limitations which include its retrospective design and potential for selection bias due to referral for ambulatory video EEG, the ambulatory video EEG appears to have a high diagnostic utility and continuing advances in technology may help in the future with technical factors and potential loss of data.

Recognition of IEDs in the absence of recorded seizures can provide evidence to support a clinical diagnosis of epilepsy. Ambulatory EEG is highly specific in identifying the occurrence of electrical spikes in persons in whom the diagnosis of seizures is being considered. Schachter and colleagues (1998) evaluated the incidence of spikes and paroxysmal rhythmic events (PREs) using a computer-assisted ambulatory EEG monitoring system in a multicenter study of asymptomatic adults (n=135) without a history of migraine or a family history of epilepsy. Spikes and PREs were evident in the overnight ambulatory EEG of only 1 asymptomatic adult (0.7%). The incidences of spikes in 24 other individuals with a history of migraine and/or a family history of epilepsy were 12.5% and 13.3%, respectively. The ambulatory EEGs of these individuals were significantly more likely to show spikes than the ambulatory EEGs of individuals without migraine or a family history of epilepsy. Olson (2001) reviewed ambulatory EEGs of 167 children when seizure-like events occurred at least 3 days per week to determine why the ambulatory EEGs were performed and whether typical seizures were recorded. Most ambulatory EEGs were performed to discriminate between epileptic and non-epileptic seizures. Ten children were recorded to determine if they were having frequent subtle seizures or frequent IEDs. The remaining 157 children had discrete events. A total of 140 children (89%) had their typical spells recorded while 107 of these children (76%) had non-epileptic events. Average duration of recording was 1.9 days. Ambulatory EEG was successful in recording children's seizure-like events when parents reported events occurring at least 3 days per week. The procedure was well tolerated and there were few technical problems with prolonged recording time.

Additional case series and retrospective studies compare and confirm higher yields of epileptiform abnormalities and clinical events captured by ambulatory EEG compared to routine EEG (Saravanan, 2001). Clinicians suggest that ambulatory EEG is superior to routine EEG in identifying both IEDs and seizures. Studies involving children and adults report a moderate to high diagnostic yield with ambulatory EEG in differentiating between seizures and non-epileptic events, quantifying seizure activity, and characterizing seizure type and location (Faulkner, 2012b; Hussain, 2013; Wirrell, 2008). Stefan and colleagues (2009; 2011) proposed the utility of outpatient ambulatory EEG (using a portable video camera in a domestic environment) as a more reliable, objective method of measuring seizure frequency to evaluate response to antiepileptic drug therapy in persons with medically refractory epilepsy.

Some persons in whom epilepsy is suspected have a normal routine or sleep-deprived EEG. An ambulatory EEG may increase the chance of detecting an epileptiform abnormality in these individuals and significantly impact clinical management. An estimated 12% to 25% of individuals who previously had a normal or non-diagnostic routine EEG have epileptiform activity on ambulatory EEG (Waterhouse, 2003). Liporace and colleagues (1998) conducted a multicenter prospective study comparing the usefulness of a sleep-deprived EEG versus a computer-assisted 16-channel ambulatory EEG in individuals with historical information consistent with epilepsy but with a normal or non-diagnostic initial routine EEG. A total of 46 participants had both a 30 to 60 minute sleep-deprived EEG and a computer-assisted ambulatory 24-hour EEG. Sleep-deprived EEG improved detection of epileptiform discharges by 24%, where ambulatory EEG improved detection of epileptiform discharges by 33%. Ambulatory EEG detected seizures in 7 of 46 (15%) participants, and in 3 participants the seizures were solely detected by the computer. Ambulatory EEG is invaluable in assessing nocturnal or sleep-related events because of its capacity to record an entire night of sleep and children can be monitored at home (Foley, 2000). In addition, an individual’s medical history may not reliably differentiate sleep-related events or disorders from epilepsy. An ambulatory EEG may record frequent arousals, suggesting sleep apnea, sustained daytime somnolence, or decreased rapid eye movement sleep latency (as in narcolepsy) and can assist in differentiating between an unsuspected sleep-related disorder and epilepsy (Waterhouse, 2003).

Ambulatory EEG is helpful at identifying seizures that are unrecognized or unreported by the individual and is easily accomplished on an outpatient basis. In both absence and focal seizures, individuals may experience brief alterations in the level of consciousness and impaired reaction time yet be unaware they are experiencing a seizure (Waterhouse, 2003). Keilson and colleagues (1987) studied 15 children, ages 5 to 16 years, with absence epilepsy using an 8-channel ambulatory cassette EEG. All 15 children demonstrated multiple paroxysms of generalized spike-and-wave discharges, most of which were asymptomatic. Therefore, ambulatory EEG may be useful in documenting the success or failure of a therapy in the treatment of absence seizures. In these situations, an ambulatory EEG of an untreated individual may show numerous daily seizures, yet normalize with adequate treatment.

Syncope or near-syncopal episodes may be evaluated with an ambulatory EEG if an ECG lead replaces one of the EEG channels (Lai, 1981). Although the underlying pathophysiological processes are distinct, seizures and syncope share some clinical characteristics which may lead to diagnostic confusion in addition to the fact that seizures and syncope may coexist in a given individual (Zaidi, 2000). Although arrhythmias have been diagnosed with continuous ambulatory EEG/ECG recording, a retrospective record review of epileptiform abnormalities in 500 individuals found epileptiform abnormalities in 1.5% of individuals with syncope and in none without a clear history of episodic complaints (Bridgers and Ebersole, 1985).

Evaluating adequate ictal and interictal EEG data is vital in facilitating localization of seizures in localization-related epilepsy (Kelly, 2011). The peer-reviewed literature reviewing the use of outpatient ambulatory EEG monitoring as the sole EEG modality in the presurgical evaluation of persons with medically refractory epilepsy consists of a single case study (Schomer, 1999) and a small case series (Chang, 2002) from the same treatment center. Chang and colleagues (2002) reported on 7 persons who underwent surgery for temporal lobe epilepsy after presurgical EEG monitoring was performed exclusively in the home setting. When compared to a group of 14 persons with similar characteristics (including age, epilepsy, duration, seizure frequency and number of antiepileptic drugs tried before evaluation) who underwent inpatient video EEG monitoring, the number of seizures captured and mean recording duration were less in the 7 persons who were evaluated with ambulatory EEG. The small, nonrandomized sample from a single institution and the retrospective design of the study make it difficult to draw conclusions regarding optimal criteria for selecting persons for ambulatory EEG in the presurgical workup.

A retrospective chart review by Primiani and colleagues (2021) reports on the yield of ambulatory EEG with video monitoring. The records of 200 individuals were reviewed. Participants younger than 12 years of age were excluded from the study. The initial reasons for ambulatory EEG with video monitoring was to capture an event in question (179/200 participants), interictal characterization (6/200 participants), and indeterminate reason (15/200 participants). There were 110 studies (55%) with clinical events recorded and 101 studies (92%) capturing recorded events on camera. Based on the video monitoring, final diagnoses were as follows: clear epileptic seizures with EEG correlate (18/200, 9%), non-epileptic events with no EEG correlate (76/200, 38%), event recorded without video capture (8/200, 4%), atypical event without EEG correlate (4/200, 2%), and no event but with clear interictal epileptiform abnormalities (22/200, 11%). Several individuals had diagnoses which were deemed inconclusive: no events and normal EEG (61/200, 30.5%) and no events with non-epileptic abnormal EEG (11/200, 5.5%). While this study has limitations including lack of information about medical management following the study, ambulatory EEG with video monitoring may be appropriate as an alternative to inpatient video EEG.

Another retrospective review by Nurse (2024) sought to ascertain the diagnostic yield of an ambulatory EEG following a routine EEG. In this instance, there were 95 individuals included. There were more epileptic seizures captured on ambulatory EEG (8%) compared to routine EEG (3%). There were no non-epileptic events captured on routine EEG and 35% were captured via ambulatory EEG. While this study has limitations including the retrospective design, the lack of assessment of reason for referral, and lack of how the information was used to diagnose or change management of condition, ambulatory EEG appears to have had a higher diagnostic yield than routine EEG and may be a suitable alternative to routine EEG in some instances.

In 2025, Doshi reported on a retrospective chart review evaluating the utility of ambulatory EEG for detecting electrographic seizures and IEDs, capturing nonepileptic events, and informing antiseizure medication withdrawal in individuals who had been seizure free for greater than 2 years. There were 309 ambulatory EEGs completed, most lasting 24 to 48 hours. In addition to the EEG, individuals reported events documented on a log. There were 10 individuals (3%) who had seizures captured on EEG, with 16 participants reporting an “event” on the log sheet. All 10 of those individuals had an established diagnosis of epilepsy. Of the 16 participants reporting an event, 14 were noted to have had an habitual event (which did not correlate with EEG) which suggested they may be non-epileptic spells. There were 88 individuals (29%) who had IEDs captured on EEG. The same 10 individuals who had seizures captured on EEG also had IEDs. Ambulatory EEG was obtained to inform antiseizure medication withdrawal in 22 individuals. Two had electrographic seizures, 4 had rare or occasional focal IEDs, 1 had frequent focal IEDs, 1 had generalized epileptiform discharges, and 14 had no epileptiform findings. Medication withdrawal was not attempted in individuals with electrographic seizures, frequent focal IEDs, or generalized epileptiform discharges. Among the 4 individuals with rare focal IEDs, 2 experienced seizure recurrence after withdrawal and 2 remained seizure-free for more than 1 year. Among the 14 with no epileptiform findings, 3 experienced recurrence and 11 remained seizure-free. The findings suggest that ambulatory EEG may identify unrecognized seizure activity and may contribute to medication-withdrawal decisions, but the small, retrospective subgroup does not establish its predictive value.

Absence seizure: A staring spell, usually brief (less than 15 seconds) in duration due to abnormal electrical activity of the brain; commonly called a petit mal seizure.

Ambulatory EEG: An EEG recorded over the course of several hours to several days outside of a health care facility.

Cardiogenic: Originating in the heart or caused by a cardiac condition.

Electroencephalography (EEG): A test that involves recording of the electrical activity of the brain (brain waves).

Epilepsy: A condition of the brain where an individual is prone to repeated seizures.

Epileptic seizure: A brief occurrence of signs and/or symptoms such as sudden and involuntary jerk of a hand, arm, or whole body, a strange smell (such as burnt rubber), a sensation in the stomach, a ringing sound that keeps increasing in volume, staring into space, or convulsive movements as a result of a primary change to the electrical activity (abnormally excessive) in the brain.

Epileptiform activity: Changes in the brain’s electrical activity that are commonly seen in people who have epilepsy.

Focal seizure: A seizure that begins with an electrical discharge in a relatively small area (called the focus) of the brain; previously referred to as a partial or localization-related seizure. In most cases, the cause is unknown, but may be related to a brain infection, head injury, stroke, or a brain tumor.

Generalized seizure: A seizure that begins with a widespread electrical discharge involving both sides of the brain at once.

Medically refractory (intractable) epilepsy: Failure of an adequate trial of two tolerated antiepileptic drug schedules to achieve sustained seizure freedom. These should be appropriately chosen and can be monotherapy or in combination.

Myoclonic seizure: Sudden, brief (less than 100 millisecond) and almost shock-like involuntary single or multiple jerks due to abnormal or excessive or synchronous neuronal activity; associated with polyspikes on EEG.

Nonconvulsive status epilepticus: Refers to a prolonged seizure that manifests as an altered mental state as opposed to convulsions seen in tonic-clonic seizures.

Paroxysmal non-epileptic events: a heterogenous group of time-limited events, characterized by changes in motor or behavioral activity which abruptly and end in a short time. These conditions can clinically simulate seizures.

Primary generalized seizure: A seizure that results from abnormal electrical activity of both sides of the brain at the same time.

Psychogenic non-epileptic seizures: A non-epileptic event that imitates a seizure and may include rhythmic movements, unresponsiveness, or other symptoms similar to those caused by epilepsy, but without an electrographic association.

Seizure: An excessive surge of electrical activity in the brain, usually lasting from a few seconds up to a few minutes, causing a wide range of symptoms or effects depending on which parts of the brain are involved in the abnormal electrical activity.

Status epilepticus: A condition in which a seizure lasts too long or when seizures occur close together and the individual doesn’t recover between seizures.

Tonic seizures: An epileptic seizure characterized by abrupt generalized muscle stiffening than can result in a fall, usually lasting less than a minute with rapid recovery.

Tonic-clonic seizure: A seizure of sudden onset involving generalized stiffening and subsequent rhythmic jerking of the limbs.

Peer Reviewed Publications:

1. Bridgers SL, Ebersole JS. Ambulatory cassette EEG in clinical practice. Neurology. 1985; 35(12):1767-1768.
2. Brigo F. An evidence-based approach to proper diagnostic use of the electroencephalogram for suspected seizures. Epilepsy Behav. 2011; 21(3):219-222.
3. Britton JW. Syncope and seizures-differential diagnosis and evaluation. Clin Auton Res. 2004; 14(3):148-159.
4. Brunnhuber F, Amin D, Nguyen Y, et al. Development, evaluation and implementation of video-EEG telemetry at home. Seizure. 2014; 23(5):338-343.
5. Casson A, Yates D, Smith S, et al. Wearable electroencephalography. What is it, why is it needed, and what does it entail? IEEE Eng Med Biol Mag. 2010; 29(3):44-56.
6. Casson AJ, Smith S, Duncan JS, et al. Wearable EEG: what is it, why is it needed and what does it entail? Conf Proc IEEE Eng Med Biol Soc. 2008; 2008:5867-5870.
7. Chang BS, Ives JR, Schomer DL, Drislane FW. Outpatient EEG monitoring in the presurgical evaluation of patients with refractory temporal lobe epilepsy. J Clin Neurophysiol. 2002; 19(2):152-156.
8. Chen Z, Brodie MJ, Liew D, Kwan P. Treatment outcomes in patients with newly diagnosed epilepsy treated with established and new antiepileptic drugs: a 30-year longitudinal cohort study. JAMA Neurol. 2018; 75(3):279-286.
9. Doshi H, Tripathi R, Alalawi Z, et al. Unique place of ambulatory EEG (aEEG) in management of epilepsy. Epilepsy Behav. 2025; 172:110516.
10. Engel J Jr, Wiebe S, French J, et al. Practice parameter: temporal lobe and localized neocortical resections for epilepsy. Epilepsia. 2003; 44(6):741-751.
11. Faulkner HJ, Arima H, Mohamed A. Latency to first interictal epileptiform discharge in epilepsy with outpatient ambulatory EEG. Clin Neurophysiol. 2012a; 123(9):1732-1735.
12. Faulkner HJ, Arima H, Mohamed A. The utility of prolonged outpatient ambulatory EEG. Seizure. 2012b; 21(7):491-495.
13. Foley CM, Legido A, Miles DK, et al. Long-term computer-assisted outpatient electroencephalogram monitoring in children and adolescents. J Child Neurol. 2000; 15(1):49-55.
14. Gilliam F, Kuzniecky R, Faught E. Ambulatory EEG monitoring. J Clin Neurophysiol. 1999; 16(2):111-115.
15. Hammill SC. Value and limitations of noninvasive assessment of syncope. Cardiol Clin. 1997; 15(2):195-218.
16. Hernandez-Ronquillo L, Thorpe L, Feng C, et al. Diagnostic accuracy of ambulatory EEG vs routine EEG in patients with first single unprovoked seizure. Neurol Clin Pract. 2023; 13(3):e200160.
17. Hussain N, Gayatri N, Blake A, et al. Ambulatory electroencephalogram in children: a prospective clinical audit of 100 cases. J Pediatr Neurosci. 2013; 8(3):188-191.
18. Keilson MJ, Hauser WA, Magrill JP, Tepperberg J. Ambulatory cassette EEG in absence epilepsy. Pediatr Neurol. 1987; 3(5):273-276.
19. Kelly KM, Chung SS. Surgical treatment for refractory epilepsy: review of patient evaluation and surgical options. Epilepsy Res Treat. 2011; 2011:303624.
20. Lagerlund TD, Cascino GD, Cicora KM, Sharbrough FW. Long-term electroencephalographic monitoring for the diagnosis and management of seizures. Mayo Clin Proc. 1996; 71(10):1000-1006.
21. Lai CW, Ziegler DK. Syncope problem solved by continuous ambulatory simultaneous EEG/ECG recording. Neurology. 1981; 31(9):1152-1154.
22. Lawley A, Evans S, Manfredonia F, Cavanna AE. The role of outpatient ambulatory electroencephalography in the diagnosis and management of adults with epilepsy or nonepileptic attack disorder: a systematic literature review. Epilepsy Behav. 2015; 53:26-30.
23. Liporace J, Tatum W 4th, Morris GL 3rd, French J. Clinical utility of sleep-deprived versus computer-assisted ambulatory 16-channel EEG in epilepsy patients: a multi-center study. Epilepsy Res. 1998; 32(3):357-362.
24. Mendiratta A. Clinical neurophysiology of epilepsy. Curr Neurol Neurosci Rep. 2003; 3(4):332-340.
25. Miller JW, Cole AJ. Is it necessary to define the ictal onset zone with EEG prior to performing resective epilepsy surgery? Epilepsy Behav. 2011; 20(2):178-181.
26. Morris GL. The clinical utility of computer-assisted ambulatory 16 channel EEG. J Med Eng Technol. 1997; 21(2):47-52.
27. Morris GL, Galezowska J, Leroy R, North R. The results of computer-assisted ambulatory 16-channel EEG. Electroencephalogr Clin Neurophysiol. 1994; 91(3):229-231.
28. Nurse ES, Freestone DR, Dabscheck G, Cook MJ. Clinical findings of long-term ambulatory video EEG following routine EEG. Epilepsy Behav. 2024; 161:110104.
29. Olson DM. Success of ambulatory EEG in children. J Clin Neurophysiol. 2001; 18(2):158-161.
30. Saravanan K, Acomb B, Beirne M, Appleton R. An audit of ambulatory cassette EEG monitoring in children. Seizure. 2001; 10(8):579-582.
31. Schachter SC, Ito M, Wannamaker BB, et al. Incidence of spikes and paroxysmal rhythmic events in overnight ambulatory computer-assisted EEGs of normal subjects: a multicenter study. J Clin Neurophysiol. 1998; 15(3):251-255.
32. Schomer DL. Ambulatory EEG telemetry: how good is it? J Clin Neurophysiol. 2006; 23(4):294-305.
33. Schomer DL, Ives JR, Schachter SC. The role of ambulatory EEG in the evaluation of patients for epilepsy surgery. J Clin Neurophysiol. 1999; 16(2):116-129.
34. Seneviratne U, Mohamed A, Cook M, D’Souza W. The utility of ambulatory electroencephalography in routine clinical practice: a critical review. Epilepsy Res. 2013; 105(1-2):1-12.
35. Stefan H, Hopfengärtner R. Epilepsy monitoring for therapy: challenges and perspectives. Clin Neurophysiol. 2009; 120(4):653-658.
36. Stefan H, Kreiselmeyer G, Kasper B, et al. Objective quantification of seizure frequency and treatment success via long-term outpatient video-EEG monitoring: a feasibility study. Seizure. 2011; 20(2):97-100.
37. Tatum WO, Winters L, Gieron M, et al. Outpatient seizure identification: results of 502 patients using computer-assisted ambulatory EEG. J Clin Neurophysiol. 2001; 18(1):14-19.
38. Waterhouse E. New horizons in ambulatory electroencephalography. IEEE Eng Med Biol Mag. 2003; 22(3):74-80.
39. Worrell GA, Lagerlund TD, Buchhalter JR. Role and limitations of routine and ambulatory scalp electroencephalography in diagnosing and managing seizures. Mayo Clin Proc. 2002; 77(9):991-998.
40. Zaidi A, Clough P, Cooper P, et al. Misdiagnosis of epilepsy: many seizure-like attacks have a cardiovascular cause. J Am Coll Cardiol. 2000; 36(1):181-184.

Government Agency, Medical Society and Other Authoritative Publications:

1. Krumholz A, Wiebe S, Gronseth G, et al. Evidence-based guideline: management of an unprovoked first seizure in adults Report of the Guideline Development Subcommittee of the American Academy of Neurology and the American Epilepsy Society. Neurology. 2015; 84(16):1705-1713.
2. LaFrance WC Jr, Baker GA, Duncan R, et al. Minimum requirements for the diagnosis of psychogenic nonepileptic seizures: a staged approach. A report from the International League Against Epilepsy Nonepileptic Seizures Task Force. Epilepsia. 2013; 54(11):2005-2018.
3. Tatum WO, Halford JJ, Olejniczak P, et al. Minimum technical requirements for performing ambulatory EEG. J Clin Neurophysiol. 2022; 39(6):435-440.
4. Velis D, Plouin P, Gotman J, da Silva FL.; ILAE DMC subcommittee on neurophysiology. Recommendations regarding the requirements and applications for long-term recordings in epilepsy. Epilepsia. 2007; 48(2):379-384.

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