Usefulness of prolonged video-EEG monitoring in the elderly

EEG and semiology in the elderly: A systematic review

INTRODUCTION

The prevalence and incidence of epileptic seizures and epilepsy increases among the elderly. Epileptic seizures in older people remain often unreported and undiagnosed, contributing to incorrect or delayed treatment. The goal of our review paper is to increase awareness of seizures in the elderly, to improve the diagnostic process in this growing population.

METHODS

We present a systematic review of the literature on EEG findings and seizure semiology among the elderly according to the PRISMA statement. One hundred and two original studies were included and findings were divided in four groups: EEG among elderly without seizures, EEG among elderly with seizures or epilepsy, semiology, and status epilepticus.

CONCLUSIONS

EEG abnormalities are found in approximately half of the geriatric population referred to routine EEG. Slowing (both focal and diffuse) is the most common finding among seniors with and without seizures. Interictal epileptiform discharges (IEDs) are likewise seen among healthy seniors, which reduces their specificity as biomarker for epilepsy. Focal onset seizures prevail among the aged. Generalized seizures are uncommon, starting usually earlier in life but exacerbating in later years. Motor phenomena are less frequently seen than among younger individuals. Seizures are mainly characterized by impairment of awareness, disturbed cognition and confusion, both ictally and postictally. Unresponsiveness may occur during non-epileptic events too, which further challenges seizure recognition. Epilepsy and dementia are bi-directionally related: dementia carries an increased risk of developing epilepsy and vice versa. Up to 45 % of the aged with new onset seizures present with status epilepticus (SE). SE among the elderly is more often focal motor; non-convulsive status epilepticus (NSCE) constitutes 10-25 %.

Clinical and Instrumental Characterization of Patients With Late-Onset Epilepsy

Epilepsy is classically considered a childhood disease. However, it represents the third most frequent neurological condition in the elderly, following stroke, and dementia. With the progressive aging of the general population, the number of patients with Late-Onset Epilepsy (LOE) is constantly growing, with important economic and social consequences, in particular for the more developed countries where the percentage of elderly people is higher. The most common causes of LOE are structural, mainly secondary to cerebrovascular or infectious diseases, brain tumors, trauma, and metabolic or toxic conditions. Moreover, there is a growing body of evidence linking LOE with neurodegenerative diseases, particularly Alzheimer's disease (AD). However, despite a thorough characterization, the causes of LOE remain unknown in a considerable portion of patients, thus termed as Late-Onset Epilepsy of Unknown origin (LOEU). In order to identify the possible causes of the disease, with an important impact in terms of treatment and prognosis, LOE patients should always undergo an exhaustive phenotypic characterization. In this work, we provide a detailed review of the main clinical and instrumental techniques for the adequate characterization of LOE patients in the clinical practice. This work aims to provide an easy and effective tool that supports routine activity of the clinicians facing LOE.

Diagnostic Performance of the Electroencephalogram in the Elderly Manifesting With Episodes of Unresponsiveness

This study aimed to determine diagnostic performance of the EEG in diagnosing seizures and to ascertain risk factors associated with seizures in the elderly presenting with episodes of unresponsiveness compared with younger patients. This is a cross-sectional study. Only EEGs requested with indication of transient unresponsiveness (TUR) were included. Patients were divided into 2 groups, younger (aged 18-49 years) and elderly (aged >60 years). The EEG was an index test. Reference standard, independently verified by 2 board-certified neurologists, was a clinical diagnosis of presence or absence of epilepsy/probable seizures. Univariate and multivariate analyses were performed to ascertain associated risk factors for epilepsy/probable seizures. Among 2187 total EEG recordings, 244 (11.16%) recordings were requested with indication of TUR. A total of 156 patients (50 younger and 106 elderly) were recruited for analysis. Prevalence of epilepsy/probable seizures in patients with TUR was 26.9%. Prevalence of interictal epileptiform discharges was 16% in the younger and 12.3% in the elderly. Overall diagnostic performance was poorer in the elderly. Associated risk factors for having seizures were presence of intermittent slow waves in the younger and presence of positive motor signs as well as presence of nonepileptiform abnormalities in the elderly. Prevalence of seizures and interictal epileptiform discharges was low in the elderly who manifests with TUR. Overall diagnostic performance of the EEG in diagnosing seizures was poorer in the elderly mainly due to low sensitivity. When we encounter patients with TUR, thorough and detailed history is still a mainstay of a diagnosis of seizures, not the EEG results.

Paroxysmal events during prolonged video-video electroencephalography monitoring in refractory epilepsy

INTRODUCTION

Given that epileptic seizures and non-epileptic paroxysmal events have similar clinical manifestations, using specific diagnostic methods is crucial, especially in patients with drug-resistant epilepsy. Prolonged video electroencephalography monitoring during epileptic seizures reveals epileptiform discharges and has become an essential procedure for epilepsy diagnosis. The main purpose of this study is to characterise paroxysmal events and compare patterns in patients with refractory epilepsy.

METHODS

We conducted a retrospective analysis of medical records from 91 patients diagnosed with refractory epilepsy who underwent prolonged video electroencephalography monitoring during hospitalisation.

RESULTS

During prolonged video electroencephalography monitoring, 76.9% of the patients (n=70) had paroxysmal events. The mean number of events was 3.4±2.7; the duration of these events was highly variable. Most patients (80%) experienced seizures during wakefulness. The most common events were focal seizures with altered levels of consciousness, progressive bilateral generalized seizures and psychogenic non-epileptic seizures. Regarding all paroxysmal events, no differences were observed in the number or type of events by sex, in duration by sex or age at onset, or in the number of events by type of event. Psychogenic nonepileptic seizures were predominantly registered during wakefulness, lasted longer, started at older ages, and were more frequent in women.

CONCLUSIONS

Paroxysmal events recorded during prolonged video electroencephalography monitoring in patients with refractory epilepsy show similar patterns and characteristics to those reported in other latitudes.

[French guidelines on electroencephalogram]

Electroencephalography allows the functional analysis of electrical brain cortical activity and is the gold standard for analyzing electrophysiological processes involved in epilepsy but also in several other dysfunctions of the central nervous system. Morphological imaging yields complementary data, yet it cannot replace the essential functional analysis tool that is EEG. Furthermore, EEG has the great advantage of being non-invasive, easy to perform and allows control tests when follow-up is necessary, even at the patient's bedside. Faced with the advances in knowledge, techniques and indications, the Société de Neurophysiologie Clinique de Langue Française (SNCLF) and the Ligue Française Contre l'Épilepsie (LFCE) found it necessary to provide an update on EEG recommendations. This article will review the methodology applied to this work, refine the various topics detailed in the following chapters. It will go over the summary of recommendations for each of these chapters and underline proposals for writing an EEG report. Some questions could not be answered by the review of the literature; in those cases, an expert advice was given by the working and reading groups in addition to the guidelines.

A critical appraisal on the utility of long-term video-EEG monitoring in older adults

BACKGROUND

World-over, the majority of patients undergoing video-EEG monitoring (VEM) are in their second or third decades. Although elderly represent the fastest growing segment of population with epilepsy, only few of them undergo VEM. We critically evaluated the utility of VEM in the diagnosis and long-term management of older adults with paroxysmal behavioral events.

METHODS

148 consecutive patients aged 45 and above, who underwent long-term (≥8 h) inpatient VEM from 1996 to 2009 formed the study cohort. Utilizing a structured proforma, we gathered their demographic, clinical, electrophysiological and long-term outcome data. VEM was considered as "useful" when it changed the diagnosis and/or management; it was "corroborative" when it helped the treating physician to confirm the diagnosis and "not useful" when it neither helped to improve the diagnosis nor the management.

RESULTS

The mean age was 51.3 (SD 6.4) years; mean duration of VEM was 69.3 h. Out of 117 patients with a diagnosis of epileptic seizures referred for presurgical evaluation or classification, VEM was "useful" or "corroborative" in 111 patients (94.8%; p=0.0001). It was also "useful" or "corroborative" in 29 out of 31 patients (93.5%) referred with a suspicion of associated or pure psychogenic non-epileptic seizures (p=0.0001). None developed any complications during monitoring. At a mean follow-up of 37.7 months there was significant reduction in AED usage in patients with epilepsy (p=0.0001) and epilepsy with associated PNES (p=0.001). At a mean follow-up of 34.2 months, all patients with pure PNES were event-free and medication-free at last follow-up (p=0.002). Twenty-three patients (19.6%) underwent surgery, all except one remaining seizure-free at a mean follow-up of 39.2 months.

CONCLUSIONS

VEM is a safe and cost-effective investigation strategy in older-adults. It aided in improving the diagnosis, offered better treatment including surgery and helped in excluding non-epileptic paroxysmal events in majority.

Video-EEG monitoring of paroxysmal events in the elderly

OBJECTIVES

To determine the importance of video-EEG monitoring (VEM) in elderly patients with various paroxysmal events.

MATERIAL AND METHODS

We retrospectively identified 16 subjects > or = 60 years old out of 834 (1.9%; 7 females, mean age 67.8 +/- 7.7 years), who were admitted to the Video-EEG Unit between 1997 and 2005 and compared data between those with and without epileptic events.

RESULTS

Epilepsy was confirmed in six patients, psychogenic non-epileptic seizures (NES) were diagnosed in seven, one patient had NES and epilepsy whereas the recorded events were non-conclusive in two. NES patients had a higher predisposition to psychiatric disturbances (P<0.02). Following VEM and management alteration, the frequency of monthly events decreased significantly for the cohort as a whole (P<0.001). VEM directly influenced the diagnosis, treatment and outcome of 14 of 16 (88%) patients.

CONCLUSION

Video-EEM plays a vital role in the evaluation of paroxysmal events in the elderly, but is vastly underutilized in this population group.

Seizure versus syncope

One of the most common but difficult management problems in medicine is that of patients who present with a paroxysmal loss of consciousness. All too often the underlying diagnosis remains elusive. This has a cost both in terms of mortality and ongoing morbidity and in terms of the financial burden associated with hospitalisation and repeated investigations. We describe a practical approach to this clinical dilemma, which is rooted in adherence to basic principles of history taking and examination, formulation of a reasonable differential diagnosis, followed by an intelligent use of specific investigations and selection of an appropriate treatment. We also discuss the effect of sudden unexpected death in epilepsy and sudden cardiac death. Despite a careful and thorough approach to the patient with a "seizure versus syncope" problem, many will require repeated assessment before a diagnosis is made.

Seizures in the elderly: Video/EEG monitoring analysis

OBJECTIVE

Recently there has been a remarkable increase in the number of elderly people with epilepsy due to the growing size of this segment of the population. The literature provides little information on the characteristics of epileptic and nonepileptic events in the elderly. Therefore we report the results of video/EEG recordings in patients aged 60 or older admitted over 2 consecutive years to an epilepsy monitoring unit (EMU).

METHODS

We examined the records of all elderly patients admitted to our EMU between December 1999 and December 2001. Fifty-eight patients were older than 60, constituting 17% of the total admissions to the EMU. All patients underwent continuous video/EEG monitoring. On the basis of reasons for admission, video/EEG reports were categorized into (1) diagnosis of events, (2) characterization and localization of seizures, (3) adjustment of medication, and (4) status epilepticus (nonconvulsive).

RESULTS

There were 26 women between the ages of 60 and 91 and 32 men between the ages of 60 and 84. The main reasons for admission were diagnosis of events (57% of patients), followed by characterization and localization of events (36% of patients). There were 6 patients with psychogenic nonepileptic seizures (PNES); 5 were women and 4 of them were >70 years of age. All PNES patients presented with motor symptoms, except for an 87-year-old man who presented with abdominal spasm. Two of these six patients were suspected of having PNES before admission. Two patients were admitted with suspicion of status epilepticus, but neither proved to have status epilepticus. The most frequent diagnosis was physiologic nonepileptic seizures (26 patients; 45%), and 27% of these patients were on antiepileptic drugs, which were discontinued after the diagnosis of nonepileptic seizures. Complex partial seizure was the most frequent seizure type, occurring in 23 patients, 6 of whom (27%) had both complex partial seizures and secondarily generalized seizures.

CONCLUSION

In the elderly, video/EEG results in a definitive diagnosis in the majority of cases and can assist in the decision whether antiepileptic drugs are necessary. PNES can occur in the elderly, and video/EEG monitoring can facilitate their recognition and management.

Characteristics of male veterans with psychogenic nonepileptic seizures

PURPOSE

To describe male patients (pts) with psychogenic nonepileptic seizures (PNESs) followed up in a Veteran's Administration (VA) seizure clinic and to compare them with those with epileptic seizures (ESs) by using clinical, and psychosocial variables.

METHODS

Adult male veterans seen between 1997 and 2000 with ESs were compared with those with PNESs with respect to clinical history (head trauma, antiepileptic drug exposure, depression, anxiety, substance abuse, seizure description), documented chronic pain, posttraumatic stress disorder (PTSD), compensation for diagnosis, neurologic examination, and test results including imaging and EEG data.

RESULTS

Men with PNESs were younger and reported more frequent events, and diagnoses of chronic pain, anxiety, and PTSD were significantly greater. Neuroimaging [computed tomography (CT) or magnetic resonance imaging (MRI) of the brain] and neurologic examination were significantly more likely to be normal or nonspecific in pts with PNESs, although history of ictal urinary incontinence or service-connected compensation for diagnosis did not distinguish the groups.

CONCLUSIONS

Male veterans with PNESs have characteristics similar to those reported in the literature, even though younger women have dominated previously studied populations. Compared with men with ESs, those with PNESs are more likely to have chronic pain, anxiety, and PTSD, as well as normal examinations and brain imaging.

Seizure Semiology in the Elderly: A Video Analysis

PURPOSE

To describe the seizure semiology of patients older than 60 years and to compare it with that of a control group of younger adults matched according to the epilepsy diagnosis.

METHODS

Available videotapes of all patients aged 60 years and older who underwent long-term video-EEG evaluation at the Cleveland Clinic Foundation (CCF) between January 1994 and March 2002 were analyzed by two observers blinded to the clinical data. A younger adult control group was matched according to the epilepsy diagnosis, and their seizures also were analyzed.

RESULTS

Fifty-four (3.3%) of the 1,633 patients were 60 years or older at the time of admission. For 21 of them, at least one epileptic seizure was recorded. Nineteen patients had focal epilepsy (nine temporal lobe, two frontal lobe, two parietal lobe, eight nonlocalized), and two patients had generalized epilepsy. Seventy-three seizures of the elderly patients and 85 seizures of the 21 control patients were analyzed. In nine elderly patients and 14 control patients, at least one of their seizures started with an aura. Eleven elderly patients and 19 control patients lost responsiveness during their seizures. Approximately two thirds of the patients in both groups had automatisms during the seizures. Both focal and generalized motor seizures (e.g., clonic or tonic seizures) were seen less frequently in the elderly.

CONCLUSIONS

Only a small percentage of the patients admitted to a tertiary epilepsy referral center for long-term video-EEG monitoring are older than 60 years. All seizure types observed in the elderly also were seen in the younger control group, and vice versa. Simple motor seizures were seen less frequently in the elderly.

Epilepsy in the elderly

BACKGROUND

Epilepsy is one of the most common neurologic diseases that affect the elderly population. Underlying etiologies as well as diagnostic and treatment issues vary from that of younger adults and deserve special consideration.

REVIEW SUMMARY

The substantially increased risk of seizures and epilepsy in the elderly is associated with medical conditions that affect this group such as stroke, dementia, and metabolic disturbances. In addition, there is an increased incidence and associated mortality of status epilepticus among seniors. Distinguishing epilepsy from paroxysmal nonepileptic events can be a particular challenge. As in the general adult population, EEG and MRI are the cornerstones of diagnostic assessment; however, the clinician must be aware of nonspecific changes associated with aging that do not necessarily indicate an underlying predisposition for epilepsy. Finally, there are unique challenges to the treatment of epilepsy in this population, but fortunately there are multiple treatment options available, including nonpharmacological therapies.

CONCLUSIONS

Knowledge of the unique challenges in identifying and treating the elderly patient with epilepsy is important for effective management as well as maximizing quality of life. However, further studies in this area are still needed to establish optimal treatment strategies.

Epilepsy and EEG in the elderly

Seizures are now the third most frequently encountered neurologic problem in the elderly population. The incidence of recurrent unprovoked seizures peaks in older patients. Because of this age-related increase and the growing elderly population, evaluation and treatment of the elderly patient has received increasing attention. This article focuses on epilepsy, not acute seizures in the elderly. The causes and types of epilepsy older individuals experience are reviewed, along with the diagnostic role of EEG. Treatment options are briefly addressed.

The usefulness of video-EEG monitoring in elderly patients with seizure disorders

The purpose of this paper was to evaluate the use of inpatient video-EEG (VEEG) monitoring in the evaluation of seizure disorders in elderly subjects. We retrospectively identified 36 patients aged 60 years old or over from a total of 849 patients studied at the VEEG unit of the Tampere University Hospital. Sixteen of the patients (44%) experienced at least one habitual seizure during the recording. Seven patients had epileptic seizures including two cases with status epilepticus. Nine patients had various non-epileptic disorders. VEEG had a clinically significant impact on the diagnosis and treatment in 14 of the 16 patients in whom paroxysmal events were recorded and proved to be useful in the evaluation of seizure disorders in elderly subjects.

Video-EEG monitoring in the elderly: a review of 94 patients

PURPOSE

We sought to determine the utility and results of video-EEG monitoring in elderly patients. There is an increased incidence of epilepsy in the elderly population. Few studies have assessed the characteristics of epileptic and nonepileptic seizures in this age group. Diagnostic evaluation with video-EEG monitoring is a means to distinguish these different types of events.

METHODS

The authors reviewed all patients aged 60 years and older who were admitted to the epilepsy monitoring unit at Columbia-Presbyterian Medical Center from January 21, 1991, to April 12, 1999.

RESULTS

A total of 94 patients and 99 patient admissions were identified, accounting for 8% of all admissions. The average age was 70 years, and the mean length of stay was 3.8 days. Typical events were recorded in 75 of the 99 patient admissions. A total of 118 seizures was recorded in 46 patients, and 98 nonepileptic events were seen in 27 patients. Of the patients with nonepileptic events, 13 had psychogenic seizures. The majority of patients with nonepileptic events were taking antiepileptic medication. Whereas 76% of the patients with epileptic events had interictal epileptiform discharges, 26% of the patients with nonepileptic events had epileptiform discharges as well.

CONCLUSIONS

Video-EEG monitoring in the elderly leads to a definitive diagnosis in the majority of patients in a relatively short time. Interictal recordings are inadequate in determining the nature of paroxysmal events. Nonepileptic events are common in the elderly, including psychogenic seizures, and these are often misdiagnosed and mistreated as epileptic seizures.

Epilepsy in Aging Populations

Older adults pose special challenges when seizures or epilepsy occur. Increased risk for seizures is often unrecognized. Older adults may have milder epilepsy, and may not require or tolerate standard doses of anti-epileptic drugs (AEDs). Polypharmacy and drug interactions are potential problems, and altered protein binding, hepatic function, renal clearance, and gastric function can affect AED dosing. Side effects such as ataxia, somnolence, and confusion are of heightened concern in this group. Older adults typically suffer localization or focal onset seizures. Although many AEDs treat these types of seizures, the AED chosen for any given patient is determined by concomitant polypharmacy, side effect profile, as well as underlying medical conditions. Free and total AED levels may be necessary. The goal of seizure management for a hospitalized patient may be rapid seizure control. As the individual moves into the outpatient setting, AED therapy without side effects and with appropriate quality of life must be pursued.

Long-term EEG monitoring: a clinical approach to electrophysiology

Long-term electroencephalographic monitoring (LTM) is the capability of recording the EEG over long periods of time and not a specific duration. Prolonged EEG recording is used primarily for epilepsy monitoring, but LTM is also used in the intensive care unit, the operating room, and in the emergency department. The purpose of LTM is to expand the limited time sampling associated with shorter "routine" EEG recording. Audiovisual monitoring may also be used in conjunction with LTM to evaluate simultaneously a specific clinical behavior that may or may not be associated with EEG alteration. This is typically performed in a hospital setting for safety and ancillary testing purposes. LTM is used most frequently in the diagnosis and management of seizures and "spells," but has also gained wider application in the evaluation of sleep disorders, cerebrovascular disease, psychiatric conditions, and movement disorders. Computer-assisted LTM systems that process, analyze, compress, and store data digitally have become widely available in clinical practice both in the hospital as well as outside the hospital when the patient is ambulatory.

Success of ambulatory EEG in children

SUMMARY

Continuous ambulatory EEG (AEEG) monitoring is a method used to (1) determine seizure type and location of seizure onset, and (2) to discriminate between epileptic and nonepileptic events. This study was performed to determine how successful AEEG would be in recording seizures when the events were reported to occur at least 3 days per week. AEEGs of children who were patients at Children's Hospital Oakland between December 1993 and June 1997 were reviewed to see why the recordings were performed and to determine whether typical seizures were recorded. Children who had seizurelike events needed to have typical spells 3 days or more per week to justify obtaining AEEG. Most AEEGs were performed to discriminate between epileptic and nonepileptic seizures. A total of 167 children underwent AEEG recording. Ten were recorded to determine whether they were having frequent subtle seizures or frequent interictal epileptiform discharges. The remaining 157 patients had discrete events. A total of 140 children (89%) had their typical spells recorded. A total of 107 of these children (76%) had nonepileptic events. Average duration of recording was 1.9 days. AEEG is very successful in recording children's seizurelike events when parents report events occur at least 3 days per week. The procedure is well tolerated and there are few technical problems that prolong recording time.

EEG and epilepsy in the elderly compared to a younger group

EEG in epilepsy in the elderly (onset > 60 yrs) was investigated (161 patients--302 EEGs) and was compared to a group of younger patients (onset 20-59 yrs) matched for sex ratio (also 161 patients--296 EEGs). In the elderly, the frequency of the background rhythm was decreased, as was the rhythmicity and amplitude. Complex partial attacks were twice as often seen in the older group, but generalized tonic-clonic seizures were more than three times as often in the younger group. The major etiology in the elderly was cerebrovascular disease, but brain tumors were found in nearly one quarter, while head injury, drug abuse, and AVM were more often seen in the younger patients. The first EEG was positive for epileptiform activity in 83%, later at 92-93% in both groups, emphasizing adequate sleep records. Although temporal lobe abnormalities were most often seen, frontal lobe discharges and slow waves were significantly more often noted in the elderly. As an example of the prominence of epileptiform activity in some elderly, PLEDs and very many discharges were seen mainly in the older group, which less often showed only rare discharges.

Value of inpatient diagnostic CCTV-EEG monitoring in the elderly

PURPOSE

To examine the outcome of inpatient diagnostic closed circuit TV-EEG (CCTV-EEG) monitoring in a consecutive series of elderly patients admitted to an adult epilepsy-monitoring unit (EMU) over a continuous 6-year period.

METHODS

Retrospective review of all admissions to a university hospital adult EMU. Those older than 60 years were identified. Patients who were monitored for status epilepticus were excluded. Data on duration of events, frequency of events, physical examination, medications, preadmission EEG, brain imaging, length of stay, and interictal and ictal EEG were obtained.

RESULTS

Of the 18 patients admitted for monitoring only, mean age was 69.5 years (range, 60-90 years). Mean length of stay was 4.3 days (range, 2-9 days). Five patients had complex partial seizures recorded. Three patients, all treated with anti-epileptic drugs (AEDs), had no spells recorded, and no additional diagnostic information was gained from the admission. The other 10 patients, eight of whom had been treated with AEDs, were symptomatic during their admission, leading to a variety of neurologic but not epileptic, psychiatric, or other medical disorders, and allowing tapering of AEDs.

CONCLUSIONS

In elderly patients with suspected epilepsy, CCTV-EEG is a very useful diagnostic tool. In this series of 18, 10 patients were diagnosed with potentially treatable medical illnesses not responsive to AEDs.

Long-term inpatient audiovisual scalp EEG monitoring

Long-term audiovisual scalp EEG monitoring is an essential diagnostic tool for the evaluation of paroxysmal disorders. The definitive classification of both nonepileptic and epileptic events is often possible only with the use of this technique. Assessment of response to treatment and the noninvasive presurgical localization of seizure foci are other important uses. The optimization of both clinical semiology and electrophysiologic data obtained from such studies is the subject of significant research efforts. Outcomes studies and advanced EEG analysis research should ultimately serve to minimize the cost of this valuable technique as well as maximizing its utility.

Interictal epileptiform activity in elderly patients with epilepsy

OBJECTIVE

To examine the frequency of interictal epileptiform activity (IEA) in elderly patients with epilepsy.

DESIGN AND METHODS

From a consecutive 13,905 EEGs recorded over 5 years at a university hospital EEG laboratory, 558 studies were performed on outpatients aged 60 years or more. Medical record review identified 125 patients in whom a confident clinical diagnosis of epilepsy was made by a board-certified neurologist. The EEG findings in these patients were reviewed. The effects of various variables on the likelihood of detecting IEA were calculated using Fisher's test and chi-square analysis.

RESULTS

IEA were present on the first EEG in 35% of 55 patients (mean age 65 years) with pre-existing epilepsy, and 26% of 70 patients (mean age 70 years) with seizure onset after 60 years. There were no significant differences in the frequency of IEA in patients with late onset epilepsy in the 7th or in the 8th decades of life. Most IEA were focal. Activation procedures added little additional information. Patients with more than one seizure per month were significantly more likely to have IEA (P = 0.016). There were no major differences in likelihood of IEA detection depending on the underlying cause of the seizures.

CONCLUSIONS

The frequency of IEA in elderly patients with epilepsy is substantially lower than that reported in epileptic populations as a whole. This low rate of IEA in routine EEG studies must be recognized when considering the diagnosis of an epileptic syndrome for episodic events happening in the elderly.