Electroencephalography in the Elderly

When the article, "EEGs in Elderly Patients: Technical and Other Considerations" was published in the American Journal of EEG Technology (AJET) in March 1980, the US elderly population was only 10% of the total US population (Hansotia et al. 1980). By the year 2030, it is projected that the elderly will account for nearly 20% of the US population (US Census Bureau 2010). Elderly patients present with a very unique presentation, suggestive of many different differential diagnoses. Elderly patients are more susceptible to seizures than the general adult population. Technologists must be knowledgeable of the normal EEG patterns, normal variants, and unique abnormalities seen in the elderly population. "Geriatric EEC is special " (Klass and Brenner 1995). KEYWORDS. EEG, elderly, epilepsy, normal variants, slowing, temporal intermittent rhythmic delta activity (TIRDA).






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Author: Davidson, Petra N
Date published: March 1, 2012

INTRODUCTION

"They are our grandparents, our parents, neighbors and friends. They are Seniors - and they are at high risk for not just diseases like Alzheimer's, heart disease and stroke, but for a more chronic and potentially more harmful disease - epilepsy." (Spitz 2005).

More than 30 years ago, Phil Hansotia, Paul Gottschalk, Philip Green, and Jerome Berendes recognized the uniqueness of the elderly population (Hansotia et al. 1980). They wrote about EEG abnormalities and artifacts exclusive to the elderly population. In the inpatient population reported by Hansotia et al. (1980), cerebrovascular disease was the most common reason for referral for an EEG. Three decades later it is evident through research that cerebrovascular disease remains the number one cause of seizures in the elderly (Figure 1) (Godfrey 1987, Stephen and Brodie 2000, Hiyoshi and Yagi 2000, Ramsay et al. 2004). Research (Leppik and Birnbaum 2010, Waterhouse and Towne 2005, Olsen 2001) further elaborates that a history of stroke is the single most common factor in elderly patients with epilepsy. Trauma is reported as the second leading cause of seizures and epilepsy in the elderly (Leppik and Birnbaum 2010, Waterhouse and Towne 2005, Olsen 2001).

EEG activation procedures did not improve diagnosis of seizures in the elderly (Hansotia et al. 1980). Hyperventilation, even when performed well, failed to yield abnormalities except to accentuate slowing. Photic stimulation failed to elicit any abnormalities in the studies reviewed (Drury and Beydoun 1998, Peltz et al. 2010, Widdess-Walsh et al. 2005, Klass and Brenner 1995).

Hansotia et al. (1980) describe the technologist's role to be one of prime importance. Without a technologist providing comfort and care to their elderly patients, the interpreter's job is useless. The technologist must be able to identify artifacts specific to the elderly population and monitor those diligently. The technologist must know how to deal with the dementia patient and exhibit great patience with the depressed and anxious elderly patient. Hansotia et al. (1980), Klass and Brenner (1995), and many others describe the elderly population as unique as the pediatrie population.

This paper will not address every essential topic related to EEG in the elderly, such as the uniqueness of nonepileptic spells in the elderly, pharmacology for the elderly with epilepsy, and antiepileptic withdrawal protocols for the elderly. This paper will concentrate on normal and abnormal EEG patterns seen in the elderly population.

DEFININGTHEELDERLY

The definition of the word elderly can be vague and can vary from source to source. Merriam- Webster (201 1) defines elderly as "rather old; especially: being past middle age or of, relating to or characteristic of later life or elderly persons." Leppik (2006) reports the origination of the term elderly describing anyone 65 years of age or older as strictly a political term used as early as 1889. Klass and Brenner (1995) suggest the terms young old (60 to 80 years of age) and old old (greater than 80 year of age). Peltz et al. (2010) add an additional group described as the oldest old (90+).

People are living longer, healthier, and more active lives. What was defined as elderly years ago is not going to be elderly in the upcoming years. Leppik (2006) states that at the time elderly was defined as 65, the average life span was 48 years old. The average lifespan now in the United States is 83 years old (Administration on Aging 2009). The definition of elderly may move from being 60+ to possibly 70 or 80+.

When the original article, "EEGs in Elderly Patients: Technical and Other Considerations" was published in AJET in March 1980, the US elderly population was only 10% of the total population (Hansotia et al. 1980). Several articles state that by the year 2030 our elderly population will encompass more than 20% of our total population (AOA 2009, Leppik and Birnbaum 2010, Trinka 2003, Bergey et al. 2006, Waterhouse and Towne 2005, Towne 2007).

The Administration on Aging (AOA) published a profile report in 2009 using US census data. This report stated that half of women over the age of 75 live alone and nearly 500,000 grandparents over the age of 65 have the primary responsibility to care for their dependent grandchildren. Many of today's elderly are community dwelling persons who are responsible for themselves and their families. They are very active, still participating in volunteer functions, teaching children, participating in active sports such as skiing and swimming, and working. The number of elderly persons in nursing homes has diminished and those who do reside in nursing homes are those that are very frail and often very old.

The community dwelling elderly do not have witnesses to their falls or syncopal episodes. Complex partial seizures, which typically occur in the elderly more often than generalized tonic clonic seizures, can be unwitnessed and unreported (Hiyoshi and Yagi 2000, Stephen and Brodie 2000, Kellinghaus et al. 2004a, Abubakr and Wambacq 2005, Keränen et al. 2002). Their spells may go undiagnosed for years, or until the elderly are admitted to the hospital with a syncopal episode that results in trauma.

DEFINING NORMAL EEG FOR THE ELDERLY

Torres et al. (1983) reported a study which discovered over 52% of EEGs in asymptomatic elderly patients would be diagnosed as abnormal if simply compared to that of healthy young adults. Healthy values of body mass index (BMI), heart rate, blood pressure, cholesterol, and other lab values are redefined for the elderly. Those normal values have been published and are constantly being revisited as the elderly population grows and as medical knowledge increases. The normal values of EEG have not yet been redefined for the elderly population as a whole.

Hansotia and colleagues ( 1 980) suggested that the characteristics of a normal EEG be defined differently for the elderly population. Many authors have attempted to address this suggestion over the past thirty years. Slowing of the posterior dominant rhythm is seen with increasing age, and is thought to be due to changes in cerebral blood flow and metabolism (Westmoreland 1982). A high incidence of intermittent temporal slowing, higher voltage of temporal rhythms than occipital rhythms, temporal intermittent rhythmic delta activity (TIRDA), and a small portion of delta transients are considered normal in the elderly (Van Cott 2002). No additional interictal epileptiform activity was obtained with activation procedures, such as photic stimulation and hyperventilation (Drury and Beydoun 1998). Peltz et al. (2010) reported EEG results on a very selective group of 12 elderly patients who were exceedingly healthy with no known medical problems. Of the 12 selected patients, only two had normal EEGs; the other patients had at a minimum slowing of the background alpha or TIRDA. Widdess-Walsh et al. (2005) found slowing of the background alpha, temporal slowing increasing with increasing age, and a high number of electrocardiogram (ECG) abnormalities.

Determining the normal patterns, normal variants, and common abnormalities in the elderly is essential. As people age their alpha rhythm, now termed posterior dominant rhythm, slows by 1 Hz and their EEG is marked by beta activity (Wang and Busse (1969). Markand (1986) presented four major changes that occur in the elderly population: 1) slowing of the alpha rhythm, 2) focal slowing in the temporal regions, 3) increased prevalence of fast activities, and 4) diffuse slow activities. Markand also noted that even in centurions the alpha rhythm (posterior dominant rhythm) should not drop below 8 Hz in healthy individuals. Westmoreland (1982) reported that in late life, particularly after age 80, the posterior dominant rhythm slows to 8 Hz, most likely due to poor cerebral perfusion.

Hansotia et al. (1980) found that the posterior dominant rhythm slows to 8.5 to 9 Hz between 60 to 90 years. Beta activity was more prevalent, most commonly occurring in the frontal regions and "regarded as a favorable sign for intellectual preservation" (Hansotia et al. 1980).

At Mayo Clinic Health System in Mankato, an EEG is interpreted as normal for patients 12 years of age and older if it has the following characteristics: 8 to 10 Hz low to moderate voltage posterior dominant rhythm during wakefulness which attenuates to eye opening, bifrontal beta in minimal amounts, and mild intermittent non-rhythmic slowing. A 91 -year-old female was scheduled for an EEG following episodes of syncope and dizziness. She reported she only passed out one time for approximately one minute, awoke and her vision was slightly distorted but denies confusion. Due to possible cardiac etiology, hyperventilation was omitted. A 10 Hz bilaterally symmetrical posterior dominant rhythm was seen with high voltage for the patient's age (Figure 2). Photic driving was also noted.

ACTIVATION PROCEDURES IN THE ELDERLY POPULATION

Cardiovascular disease and pulmonary dysfunction contraindícate hyperventilation in many elderly patients, and hyperventilation is difficult to obtain in patients with moderate to severe cognitive decline.

Hyperventilation, when completed, only demonstrated accentuation of temporal slow transients in one-fifth of normal elderly patients per Klass and Brenner (1995). Angus-Leppan (2007) performed a study of 1000 EEG records and noted that, hyperventilation was only performed on 580 patients; all patients over the age of 50 were barred from doing hyperventilation. 29 of the 580 patients had abnormalities during hyperventilation. Drury and Beydoun (1998) reported no significant changes with hyperventilation. Hyperventilation was omitted in studies by Widdess-Walsh et al. (2005) and Peltz et al. (2010). Drury and Beydoun (1998) reported no significant changes with hyperventilation.

In multiple studies, no abnormal results from photic stimulation were seen in a total of over 1500 elderly patients (Widdess-Walsh et al. 2005, Peltz et al. 2010, Drury and Beydoun 1998, Klass and Brenner 1995).

Angus-Leppan (2007) reported the yield of sleep as an activation procedure to be 97.1% specific, whereas hyperventilation is less than 0.10% and photic stimulation 0%. None of patients who had clinical seizures during activation procedures were over 40 years of age.

NORMAL VARIANTS IN THE ELDERLY

What constitutes a normal variant in the elderly is debated among electroencephalographers. Westmoreland (1982) stated that there is more low voltage activity and a greater amount of temporal transients, particularly slowing in elderly EEGs. Peltz et al. (2010) performed a study on 12 healthy oldest old (90+) and found that 10 of those had abnormal EEGs due to intermittent temporal slowing, slowing of the background alpha under 8 Hz, and TIRDA. These authors suggested that perhaps TIRDA and other intermittent slowing is simply a normal variant of this age group.

Three benign EEG variants that occur more frequently in the elderly are subclinical rhythmic electrical discharge of adulthood (SREDA), wicket spikes, and small sharp spikes (Waterhouse and Towne 2005). Westmoreland (1982) stated that "temporal transients are seen in normal subjects after the age of 40 years, with a left sided preponderance. Temporal transients increase in prevalence in the fifth and sixth decades."

ABNORMALITIES OF THE ELDERLY EEG

Decreased reactivity of alpha rhythm; absence of frontal beta; presence of diffuse, generalized theta; and delta slowing are indicative of intellectual deterioration (Hansotia et al. 1980). A significant asymmetry between hemispheres of 1 Hz or more is considered abnormal (Westmoreland 1982). Common abnormalities in elderly EEGs are diffuse slowing in those with encephalopathies and focal slowing in the presence of a lesion (Waterhouse and Towne 2005).

Dementia and Encephalopathy

Alzheimer's Disease. In patients with Alzheimer's disease, the resting alpha frequency declines, some disorganization of the record may occur, and reactivity may be altered (Neiman et al. 2009). In the late stages of Alzheimer's disease, periodic epileptiform discharges such as bilateral independent periodic lateralizing epileptiform discharges (BIPLEDs) and triphasic waves can be seen. Patients with Alzheimer's disease have the following abnormalities on their EEGs: suppressed alpha, slower alpha, higher theta, and desynchronized activity (Neiman et al. 2009).

Encephalopathies. Neiman and Hanna (2009) present a disease specific list of EEG changes for many different encephalopathies. Delta and theta intermixed with the posterior dominant rhythm may be the first EEG sign of encephalopathy. As the encephalopathy increases, the amount and amplitude of the slow-wave activity increase. Frontal intermittent delta activity (FIRDA) is non-specific but may be seen in patients who are encephalopathic but awake or mildly lethargic.

Tumors, Bleeds, Strokes, Other Lesions

Olsen (2001) reports nonspecific findings for post stroke EEGs. If periodic lateralized epileptiform discharges (PLEDs) or focal spikes are found after a stroke, a patient's risk for epilepsy is increased above the normal population (Leppik and Birnbaum 2010). 60% of status epilepticus is caused by acute or remote symptomatic stroke in the elderly (Towne 2007).

Epileptic Patterns of the Elderly

Interictal epileptiform discharges are rarely seen in elderly EEGs (Bergey et al. 2006, Van Cott 2002, Drury and Beydoun 1998). Elderly patients have a greater probability of a non-diagnostic routine EEG. Prolonging the recording or including video and monitoring for days increases the yield significantly (Towne 2007, Ramsay et al. 2004). Towne reported on a study by Marsan and Zivin from 1970 which states that interictal epileptiform activity occurs less often in our elderly than other age groups (Towne 2007).

While the overall epileptiform discharges do not differ in shape, irregular spike and wave or polyspike complexes are more common in the elderly (Klass and Brenner 1995). The specificity of EEG should be strongly considered with respect to an epileptic diagnosis in the elderly as 12% of EEGs in normal elderly people contain spike waves (Godfrey 1987).

A 73-year-old female presented to the EEG lab following a change in her antiepileptic medication regimen. The patient had a history of epilepsy. No further history could be obtained from the patient. The patient's posterior dominant rhythm was only 6 to 7 Hz on the left and 8 Hz on the right (Figure 3). Spike and wave discharges were seen predominately in the left posterior region. Sleep activated the spike and wave discharges. Slowing was present over the entire left hemisphere. Bursts of right hemispheric rhythmic slowing were also seen.

Partial seizures account for half of all seizures in the elderly (Godfrey 1987). In a study conducted at the National Epilepsy Center in Japan, 145 of 190 elderly patients with known epilepsy were confirmed to have partial epilepsy (Hiyoshi and Yagi 2000). Van Cott (2002) reports 48% of elderly patients with known seizures have complex partial seizures.

Nonconvulsive status epilepticus

Beyenburg et al. (2007) define nonconvulsive status epilepticus in two forms, generalized and focal. The elderly are more likely to have focal nonconvulsive status. Nonconvulsive status is now recognized as a medical emergency. It is easily misdiagnosed as mental status changes, delirium, confusion, and coma of unknown origin or other altered awareness. The mortality rate of nonconvulsive status in patients with other health problems is as high as 57% in intensive care patients (Beyenburg et al. 2007).

MAYO CLINIC HEALTH SYSTEM DATA

Over 1100 elderly EEGs have been performed in the last six years at Immanuel St. Joseph's Hospital, including all outpatients to Mayo Clinic Health System Specialty Clinic and Heart Center, and for multiple outlying smaller communities in south central Minnesota. Half of each gender made up inpatient and outpatient referrals. Staying on course with other major studies, less than one third of these elderly patients had normal EEGs (Figure 4). Patients were referred for EEG for five major reasons: mental status change, spells, seizures, strokes, and encephalopathy (Figure 5).

EEG abnormalities were divided into three basic categories: epileptiform, nonspecific irregularities, and slowing. Slowing was the most frequent abnormality at 47% of the patients. Epileptiform and nonspecific irregularities were seen in 35% and 18% respectively (Figure 6).

EPILEPSY IN THE ELDERLY

Several facts are consistently noted in nearly every article regarding epilepsy in the elderly:

1) the elderly succumb to seizures and epilepsy more than any other age group,

2) the largest identifiable cause of seizures and epilepsy in the elderly is cerebrovascular disease,

3) the symptoms of seizures and epilepsy in the elderly are more vague than in younger adults,

4) finding an appropriate treatment for the elderly is complicated by adverse drug reactions, drug interactions, polypharmacy, absorption rates, and other challenging health issues,

5) approximately 100 in every 100,000 patients over the age of 65 experience a seizure or epilepsy.

The brain initially matures and develops at a very rapid rate which occasionally results in problems with the maturation process; conversely the brain also begins to atrophy more quickly towards the end of life.

Case Study

Nearly six years ago, a 65-year-old female was referred to the sleep lab for evaluation of obstructive sleep apnea. The technologist scoring her sleep study noticed some sharp waves and other interictal discharges. These epileptiform changes were noted in the technologist's report. The referring physician, an epileptologist, then referred her for an EEG. He also referred her to the balance lab for evaluation of dizzy spells. Her dizzy spells were diagnosed as central vertigo. When she came for her EEG, the technologist asked how she was handling her dizzy spells. She stated that they were still happening frequently and no one was quite sure why. Generalized bursts of spike and wave activity were seen on the patient's EEG (Figure 7). The technologist asked the patient how she was feeling and she reported her same dizzy feeling. As the EEG progressed, the technologist asked her to report any time the dizzy spells began or became worse. It was noted on the EEG that every time the patient reported an increase or onset of dizziness, there was a burst of generalized spike and wave activity. She was diagnosed with partial epilepsy with dizziness as her primary symptom.

During the summer of 2010, the same patient returned to the Balance Clinic, referred from her primary care provider for dizziness. The patient also reported that she lost moments in time frequently. The coordinator for the Balance Center reviewed her records and discovered she had not had an EEG in six years, and was reporting no seizures for six years. An EEG was ordered. Her EEG contained very frequent generalized spike and wave activity. She was seen in the epilepsy clinic the same day for medication changes. The patient's seizures which consisted of dizzy spells and lost moments in time are now under control, thereby increasing her quality of life.

AN EEG DESIGNED FOR THE ELDERLY

The most common barrier to an artifact free recording in elderly patients is excessive movement. A helpful start to any EEG is ensuring the comfort of the patient. Prompting the patient to use the restroom prior to starting the test or offering a glass of water or a blanket can help ensure the patient's comfort prior to recording.

For confused patients and those with other mental status changes, reminding them where they are and who staff is, as well as allowing a family member or caregiver to be present, often eases their fears and anxieties about the EEG.

As simple as it sounds, remembering to be patient and understanding also helps a great deal. For elderly patients, extra diligence is necessary to ensure the patient can hear the technologist and understand what is being done. Some patients do not want to admit they need hearing assistance. Reminding patients that they cannot touch their hair or move about during the test is also essential.

Enabling a patient to relax promotes decreased beta, increased voltage, clarity of posterior dominant rhythm, and decrease in the amount of muscle tension. The patient is also much more likely to fall asleep naturally, therefore increasing the ability to capture an electrographic recording of sleep and sleep induced abnormalities.

Activation procedures are of limited value in the elderly (Drury and Beydoun 1998, Klass and Brenner 1995). Hyperventilation is contraindicated in acute cardiac, cerebrovascular, respiratory, and pulmonary diseases. Obtaining adequate participation is challenging in patients suffering from cognitive and mental decline. Obtaining an adequate history, which may contraindícate hyperventilation, is often difficult with patients from nursing homes and assisted living facilities.

Photoparoxysmal responses are rare in the elderly and when they are found the most probable explanations are drug withdrawal states or electrolyte changes (Klass and Brenner 1995). In a study of 125 patients, during which a total of 139 EEGs were performed, only three patients showed an increase in interictal epileptiform activity during activation procedures (hyperventilation, photic stimulation, and sleep) and no patient had interictal activity during an activation procedure alone (Drury and Beydoun 1998).

Extended EEG recordings and ambulatory EEG recordings increase the yield of epileptiform activity by 50% (Ramsay et al. 2004). All studies reporting results on video EEG and long-term monitoring in the elderly report a stark drop in the number of patients referred to long-term monitoring and video EEG monitoring labs after the age of 60.

Every article addressing epilepsy in the elderly reports a wide breadth of clinical symptoms including: dizziness, syncope, memory loss, odd behaviors, changes in pallor, sweating, vertigo, nystagmus, numbness, weakness, fatigue, irritability, aggression, confusion, aphasia, and disorientation.

SUMMARY

The elderly population presents a unique challenge not only to the electroencephalographer but also to the technologist. Elderly patients rely on the technologist to be acutely aware of their needs, comfort, the medical conditions specific to their age group, normal EEG patterns, normal EEG variants, and the EEG abnormalities that exist only in their age group. The population as a whole is aging and the elderly population will blossom as the baby boomers become age 60 years and older. An entirely new generation of elderly people will cause an even greater need for elderly EEGs to be fine tuned.

Additionally, it is worth noting that "spells" may be due to another issue. A 77year-old patient was referred for an EEG due to "syncope" characterized by a brief loss of consciousness. During the EEG, the patient had an episode of asystole (Figure 8). His EEG slows briefly while the asystole is occurring, then immediately after the heart begins to beat effectively, the EEG speeds up and beta activity is seen.

CONCLUSION

The greatest population at greatest risk for epilepsy and seizures is the elderly population. The elderly population presents with seizures differently than any other population. Their complex partial seizures include symptoms such as confusion, memory loss, dizziness, and shortness of breath. There may be compounding factors such as nonepileptic spells. Today's elderly are taking care of themselves far longer and in more isolation than previous times. They are also remaining as caregivers for longer, often caring for their grandchildren. These elderly patients depend on quality EEGs and other tests designed to capture and diagnose their spells.

The most common cause of seizures in the elderly population has been and remains to be cardiovascular problems, specifically strokes. The abnormalities seen on an elderly EEG may be very subtle and the normal elderly EEG may easily be misinterpreted as abnormal if the nuances of elderly EEG are not considered.

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Author affiliation:

Petra N. Davidson, R. EEG T., BS;

Keith A. Davidson, BA

Mayo Clinic Health System

Mankato, Minnesota

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