NADD Bulletin Volume III Number 3 Article 1

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Dementia Evaluations in Persons with Mental Retardation: They Don’t All Have Alzheimer Disease

Kate Haller, MD


As the population of people with mental retardation ages, concerns about dementia are becoming far more common. If a person is elderly or has Down syndrome, almost any change in behavior raises concern among family and other caregivers about the possibility of Alzheimer disease (AD). This paper will review the definition of the dementia syndrome, and some of its causes, and will discuss ways of differentiating between dementia and other causes of behavioral changes. The elements of an appropriate dementia evaluation will be discussed.

Dementia and Developmental Disabilities

There is increasing interest in the problems associated with aging in people with mental retardation. The aging of the population with developmental disabilities parallels or exceeds the “graying” trend widely noted in the general population. In the U.S., the population of people over 60 who have a developmental disability is projected to increase from an estimated 173,000 in 1995 to 332,900 by the year 2025 (AAMR-IASSD Work-group, 1995). In addition, dementia becomes common among people with Down syndrome who reach middle age. While people with Down syndrome continue to have a shorter life expectancy than most, we now see many in their late forties and fifties, when an Alzheimer type dementia becomes common (Nelson, Lott, Touchette, Satz, & D’Elia, 1995).

Older people with developmental disabilities comprise a relatively unstudied group. Until recently, a shortened life span was expected for people with mental retardation, and services and research were geared toward serving children (Syzmanski et al.,1991). For instance, our program, the Developmental Disabilities Center, is a part of a department of pediatrics although we provide most of our service to adults.

In the general population, dementia is typically suspected because the person is showing clear signs of forgetfulness, especially gaps in short-term knowledge, word-finding difficulties, and deterioration in spatial skills (e.g. getting lost in relatively familiar surroundings). Because of their typical past functioning, one can assume that individuals’ inability to answer simple questions, recall events, or carry out directions is indicative of cognitive loss. A widely-used screening test, the Mini Mental State Exam (Folstein, Folstein, & McHugh, 1975), has a thirty-point possible score. Scores below twenty are considered highly indicative of dementia in the general population.

The situation is different with the people we work with. Often the reason for referral is a behavior change, like “He’s hitting people,” or “She won’t go to the work program,” or “He’s incontinent,” and changes in memory are less clear-cut. This is especially true for individuals with limited or no verbal abilities and few complex skills, or for persons whose caregivers have changed repeatedly recently. One cannot assume what a person’s previous level of functioning may have been. The Mini Mental score will be low, but how low is “normal” for this person?

The Clinical Syndrome of Dementia

Dementia is not one illness—it is a syndrome, i.e. a recognizable pattern of clinical findings. Conceptually, medical diagnosis starts with recognizing a pattern of signs and symptoms—a syndrome—and then proceeds to establishing a specific diagnosis. In actual practice, this distinction is not always clear. In discussions of dementia, Alzheimer disease is often equated with dementia syndrome, whereas in fact AD is only one of many possible causes (albeit the most common.)

The syndrome of dementia consists of a loss of memory, plus deterioration in other cognitive abilities. Memory loss must eventually become apparent in any case of dementia, but it is not always the first sign to appear. Typically, short-term recall is affected first. Thus, a person may recall details of their childhood but be unable to recall significant recent events. Difficulty learning new information becomes apparent. For example, a group-home resident may be unable to learn names of new staff while still retaining those of long-term caregivers. A person may forget that a meal has already been eaten, or be unable to carry out directions that involve multiple steps or a decision. A decreasing IQ may be seen on repeated psychological testing.

Aphasia (loss of language), agnosia (loss of the ability to recognize people and objects), and apraxia (loss of the ability to carry out learned sequences of movement) are additional memory-related losses. Word-finding problems are very common—the person may start to refer to objects by incorrect or vague terms. A loss of receptive language may be evidenced by loss of the ability to pick out an object someone else has named. Apraxia and agnosia would be suspected when a person no longer seems to recognize what to do with objects they formerly used, or how to carry out familiar routines; such as using appliances, dressing themselves, using the phone, eating with utensils, signing their name, using the toilet. In all of these areas, obviously the evaluator must know what the person was formerly able to do.

In addition to memory problems, the person with dementia loses other cognitive abilities such as the ability to reason, to think abstractly, and/or the ability to plan actions and solve problems. It may appear that the person has worsening judgment or has become more impulsive, aggressive, or easily frustrated. Modesty and self-control may be diminished. Often initiative is greatly reduced, and the person becomes apathetic.

Dementia can be diagnosed only if there is definite evidence of memory loss and cognitive deterioration, and these must not be primarily due to another cause (American Psychiatric Association, 1994) such as loss of language abilities due to increasing deafness, or apathy due to hypothyroidism.

Along with the specific syndrome-defining problems described above, associated symptoms may occur. Depression is common, and psychotic symptoms such as visual hallucinations and persecutory beliefs may occur. Sleep disturbances and agitation are common. “Catastrophic reactions” (panicky agitation) to changes may occur, as well as increased anxiety and clinging behaviors. As dementia then progresses, problems such as incontinence and seizures and myoclonic jerks (sudden involuntary limb movements) may be seen. Each of these can occur for various reasons other than dementia, and the diagnosis of dementia should not be made unless the core features of the syndrome are present.

Differential Diagnosis

One feature which is usually absent from early dementia is altered level of consciousness. The person is typically alert though confused. A fluctuating level of consciousness is the hallmark of delirium, a clinical syndrome distinct from dementia. Delirium may be due to medications, low oxygen levels, low blood sugar, intoxication with various substances or withdrawal from them, or infections or other medical causes. Most typically, its onset is fairly abrupt, but when it is relatively insidious it can be mistaken for dementia. If there is any suspicion of delirium, a medical search for its possible causes is the priority. In elderly or frail people, delirium may be the only sign of an acute, life-threatening illness such as sepsis, pneumonia, or kidney infection.

Depression is very common in elderly persons and in adults with Down syndrome. Characteristics include sad or irritable mood, loss of enjoyment in usually-pleasurable activities, and changes in sleep, appetite and energy. Often the person is notably “slowed down” in movement and thinking, and may stop doing tasks of which they were previously capable, making caregivers suspect dementia. Depressed mood and thoughts may be difficult to detect because of limited verbal skills. Since depression is readily treatable, careful consideration of the possibility of depression should be part of every dementia evaluation.

Loss of physical abilities, including vision, hearing, and mobility, can cause a decline in functioning that can mimic dementia. Sometimes this has been called pseudodementia, a term also applied to some depressions, but this term tends to be confusing.

Causes of Dementia

When dementia is clinically present, and depression and delirium have been ruled out (or diagnosed and treated, without resolution of the apparent dementia), further investigations may enable a diagnosis of a specific cause of the dementia. A “dementia work-up” does not determine whether a person is demented or not, but is a search for conditions which may account for the dementia which is clinically diagnosed. Most dementias are irreversible, but it is especially important to look carefully for those causes which can be treated and reversed. A careful review of the person’s medications should be done in all cases. A number of medications, including sedative-hypnotics and anticholinergics, are commonly prescribed for elderly persons, and are known to have cognitive impairment as a side effect. These medications should be stopped. Other medications may occasionally contribute to or actually cause a reversible dementia in some cases. Stopping the medication may be the only way to determine this, and should be considered in many cases. (Gedye 1999). In our clinic, we have seen lithium and valproic acid cause dementias which were reversed when the medication was stopped.

Most cases of dementia are of three types, none of which have a specific, generally-accepted diagnostic test. These are Alzheimer disease (AD), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD). Of these, AD is by far the most common. (Hirono et al., 1999).

Most cases of dementia are due to a particular brain disorder called Alzheimer disease (AD), accounting for most dementia cases in the non-DD and DD population alike (Wisniewski, Silverman, & Weigiel, 1994). Currently, there is no test which positively diagnoses AD in living subjects, though this may change soon, as research is very active in this area (Skoog, Marcusson, & Blennow, 1998). Thus, the diagnosis should correctly be “probable Alzheimer disease” in living people. EEG and CT or MRI findings may support the diagnosis, but are mainly valuable to rule out other, less common causes of dementia. Alzheimer disease is generally diagnosed by eliminating other possible causes in a person with clinical findings consistent with this diagnosis. In cases in which the clinical picture is ambiguous, it is often necessary to repeat clinical assessments (patient and caregiver interviews) at intervals of at least several months before making a diagnosis.

A great deal of research is now being done on genetic risk factors for Alzheimer disease, with at least eight genes so far identified as affecting people’s risk of disease and/or the age of onset. But as of this writing, DNA studies are not useful clinically in determining whether a particular person’s illness is due to AD or another cause, or due to multiple causes, and therefore they are not in routine clinical use.

There are specific neuropathological findings seen at autopsy which in the general population are considered specific for Alzheimer disease. The same types of changes can be seen in virtually all people with Down syndrome after age forty, yet not all have clinical dementia (Janicki, Heller, Seltzer, & Hogg, 1995). Down syndrome is associated with the development of Alzheimer disease at relatively early ages. The average age of onset is probably in the early fifties (Burt et al., 1998; Visser et al., 1997). Alzheimer disease occurs in almost all people with Down Syndrome by age seventy, although there is a documented case of survival into the eighties without dementia (Chicoine & McGuire, 1997). In people with Down Syndrome who are under forty, behavioral changes are generally due to causes other than Alzheimer disease (Gedye, 1995).

After AD, the next most common specific cause of dementia in the general population may be dementia with Lewy bodies (DLB) (McKeith et al., 1996). Awareness of this disorder is increasing among clinicians, and it may account for fifteen percent of cases of dementia in the general population (McKeith, O’Brien, & Ballard, 1999). Like AD, DLB is diagnosed by history and examination of the patient, and not by any lab test or X-ray. Lewy bodies are a microscopic abnormal finding in brain tissue, typically occurring in Parkinson’s disease in the basal ganglia, brain areas associated with initiating and controlling voluntary movements. It has long been noted that some Parkinson’s patients also develop dementia. In these cases, Lewy bodies are also present in the cortex, which is involved in memory, thinking, etc. It now appears that some people develop cortical Lewy bodies (and dementia) without developing Parkinson’s disease. The distinctive clinical features include fluctuating cognitive level, which can resemble delirium; persistent visual hallucinations; and spontaneous features of Parkinsonism (such as resting tremor, changes in gait, muscle rigidity, or lack of facial expressions). Memory loss may not be evident early on, when other symptoms such as unexplained falls may dominate the clinical picture. (Galasko, 1999). Although there is no specific treatment for DLB, it is important to recognize this diagnosis because these patients are likely to have severe side effects from antipsychotic medications, such as would commonly be prescribed for hallucinations (McKeith, Fairbairn, Perry, Thompson, & Perry, 1992).

A third type of dementia, frontotemporal dementia (FTD), is named for the brain areas that are most affected. Loss of good judgment, and the development of apathetic or euphoric moods, and the emergence of uninhibited, socially-inappropriate behaviors may be very prominent. FTD includes the diagnosis of Pick’s disease and certain other dementias. Its incidence is uncertain, in part because it may overlap clinically with the preceding diagnoses (Hirono et al., 1999).

Vascular dementia, formerly known as multi-infarct dementia, accounts for a small fraction of dementia cases. It results from accumulated brain damage from multiple small strokes, which individually may not be clinically obvious though classically a stepwise progression is described. It is diagnosed by the documentation of specific neurological deficits such as unilateral weakness or abnormal reflexes and by evidence of multiple strokes on CT scan or MRI of the head. There is often a history of hypertension (American Psychiatric Association, 1994).

Less common causes of dementia include a variety of medical conditions. Treatment of the underlying condition may reverse the dementia, or at least stop its progression. A complete physical and neurological exam is mandatory. Lab tests including complete blood count, chemistries, thyroid panel, B12 and folate levels, erythrocyte sedimentation rate, and syphilis serology should be obtained in any individual in whom dementia is suspected. Depending on the individual’s history and examination, further blood tests may be warranted, such as HIV testing (American Psychiatric Association, 1997).

Neuroimaging (a CT scan or MRI of the head) should be performed. Dementia can follow head trauma due to brain injury, or occasionally may be due to an accumulation of blood (chronic subdural hematoma) exerting pressure on the brain. In the latter case, surgical treatment may cure or reduce the dementia dramatically. Brain tumors (primary or metastatic) could present as dementia. Normal pressure hydrocephalus (which presents with dementia, gait changes, and incontinence) may respond to placement of a shunt in some cases. Most commonly, a CT done as part of a dementia evaluation will be normal or show brain atrophy. Sometimes a pattern of localized atrophy of the frontal and temporal cortex is seen. If correlated with clinical findings of dementia with markedly disinhibited behavior (loss of modesty, inappropriately mouthing or eating non-food items, or impulsive sexual behavior), this would support a diagnosis of frontotemporal dementia. A demented person can also have a normal CT scan, especially early in the course of illness. Conversely, many people with mental retardation, and many normal older adults, have some degree of brain atrophy. If the individual has had previous CT scans for any reason, comparison of new and old films is helpful. Relatively rapid progression of atrophy may be indicative of a dementing illness.

Other testing can be done if the clinical situation calls for it; for instance, a lumbar puncture (spinal tap) to obtain cerebrospinal fluid if a central-nervous-system infection is suspected. Sleep-lab studies can be done to rule out sleep apnea, for example in a patient who is known to snore (Steiner, Ward, & Ali, 1999).

What to Bring to a Dementia Evaluation

When dementia is suspected, the primary care doctor should be notified of this concern. He or she will medically evaluate the individual and, if appropriate, make a referral to the psychiatrist. The psychiatrist must be provided with adequate data about the person’s normal level of functioning as an adult, to use as a basis of comparison. At our clinic, caregivers are requested to complete the Adaptive Behavior Scale prior to the first mental health visit for any reason. Later, if dementia is suspected, this can be repeated for comparison. In most cases, however, the medical records will not contain a detailed picture of a person’s usual abilities. We have found that many other types of records can be helpful, including past psychological test reports (IQ tests), special education reports, and institutional discharge summaries. Mandated annual evaluations (IHPs, Individual Habilitative Plans in our state) describe habilitative goals from which levels of functioning can be inferred. Social histories and updates may contain information that is useful as to what the individual could do at an earlier point. Old records often include examples of the person’s signature, which can be compared with a new signature for completeness and accuracy. The caregiver seeking the evaluation should assemble relevant records and send copies in advance to the evaluating physician.

When the actual evaluation takes place, the individual should be accompanied by one or two caregivers or others with daily contact with the person. At least one person should attend who has known him/her since prior to the onset of the behavior changes which are causing concern. The person being evaluated should generally be present at this interview and encouraged to participate. A structured caregiver interview such as the Down Syndrome Dementia Scale (Gedye, 1995) may be used, or a written questionnaire may be completed.

The psychiatrist should interview the person himself/herself. When possible, at least part of the interview should be private, without caregivers present, unless the individual cannot separate from the caregiver, or is so impaired in communication as to make this impractical. If the caregivers are present, they should allow the physician to interact directly with the person unless asked to “translate” in either direction. In addition to assessing mood, and thought content if the individual is able to communicate verbally, the physician will be looking at how the person relates socially, their level of alertness, and looking for evidence of sensory or medical problems that can interfere with performance. The person will be asked to follow some simple directions and memory will be assessed.

The initial appointment should end with a review of the clinical issues, including an assessment of whether the syndrome of dementia is definitely present, definitely absent, or uncertain. The possibility of other problems, especially psychiatric or medical illness, should be considered and priority given to addressing these. A referral to a neurologist or a testing psychologist will be appropriate in some cases. Lab tests or X-rays will not determine the presence or absence of the syndrome of dementia. If dementia has been diagnosed, or is suspected but uncertain, these tests are useful to rule out medical problems that occasionally cause dementia. Normal results can occur in people with the commonest types of dementia, as well as in people who are not demented at all.

A hasty diagnosis of Alzheimer’s disease can do a disservice to the person, especially if it results in reversible conditions being overlooked (Zigman, Schupf, Haverman, & Silverman, 1995). It is preferable to accept a degree of uncertainty initially. Repeated evaluations over a period of several months are often needed before a definite diagnosis is made.


AAMR-IASSD Work-Group on Epidemiology and Alzheimer Disease. (1995). Epidemiology of Alzheimer disease in mental retardation. Washington, DC: AAMR.

American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author.

American Psychiatric Association. (1997). Practice guideline for the treatment of patients with Alzheimer’s disease and other dementias of late life. American Journal of Psychiatry, 154 (supplement), 1-39.

Burt, D. B., Loveland, K. A., Primeaux-Hart, S., Chen, Y. W., Phillips, N. B., Cleveland, L. A., Lewis, K. R., Lesser, J., & Cummings, E. (1998). Dementia in adults with Down syndrome: Diagnostic challenges. American Journal on Mental Retardation, 103, 130-145.

Chicoine, B. & McGuire, D. (1997). Longevity of a woman with Down syndrome: A case study. Mental Retardation, 35, 477-479.

Folstein, M., Folstein, S., & McHugh, P. (1975). Mini mental state, Journal of Psychiatric Research, 12, 189-198.

Galasko, D. (1999). A clinical approach to dementia with Lewy bodies. The Neurologist, 5, 247-256.

Gedye, A. (1995) Dementia Scale for Down Syndrome (Manual). Vancouver, BC: Author.

Gedye, A. (1999). Neuroleptic-induced dementia documented in four adults with mental retardation, Mental Retardation, 36, 182-186.

Hirono, N., Mori, E., Tanimukai, S.,, Kazui, H., Hashimoto, M., Hanihara, T., & Imamura, T. (1999). Distinctive neurobehavioral features among neurodegenerative dementias, Journal of Neuropsychiatry and Clinical Neuroscience, 11, 498-503.

Janicki , M. P., Heller, T., Seltzer, G. B., & Hogg, J.(1995). Practice guidelines for the clinical assessment and care management of Alzheimer and other dementias among adults with mental retardation, Washington, DC: AAMR.

McKeith, I., Fairbairn, A., Perry, R., Thompson, P., & Perry, E. (1992). Neuroleptic sensitivity in patients with senile dementia of the Lewy body type, British Medical Journal 305, 673-678.

McKeith, I., Galasko, D., Kosaka, K., Perry, E. K., Dickson, D. W., Hansen, L. A., Salmon, D. P., Lowe, J., Mirra, S. S., Byrne, E. J., Lennox, G., Quinn, N. P., Edwardson, J. A., Ince, P. G., Bergeron, C., Burns, A., Miller, B. L., Lovestone, S., Callerton, D., Jansen, E. N., Ballard, C., deVos, R. A., Wilcock, G. K., Jellinger, K. A., & Perry, R. H. (1996). Consensus guidelines for the clinical and pathologic diagnosis of dementia with Lewy bodies (DLB): Report of the Consortium on DLB International Workshop. Neurology 47, 1113-1124.

McKeith, I. G., O’Brien, J. T., & Ballard, C. (1999). Diagnosing dementia with Lewy bodies. The Lancet, 354, 1227-1228.

Nelson, L., Lott, I., Touchette, P., Satz, P., & D’Elia, L. (1995). Detection of Alzheimer Disease in individuals with Down syndrome. American Journal on Mental Retardation, 99, 616-22.

Skoog, I., Marcusson, J., & Blennow, K. (1998). Dementia: It’s getting better all the time. The Lancet End of Year Review, 352, 4.

Steiner, M., Ward, M., & Ali, N. (1999). Dementia and snoring. The Lancet, 353, 204.

Szymanski, L., Madow, L., Mallory, G., Menolascino, F., Pace, L., & Eidelman, S. (1991) Report of the task force on psychiatric services to adult mentally retarded and developmentally disabled persons. Washington, DC: American Psychiatric Association.

Visser, F. E., Aldenkamp, A. P., van Huffelen, A. C., Kuilman, M., Overweg, J., & van Wijk, J. (1997) Prospective study of the prevalence of Alzheimer-type dementia in institutionalized individuals with Down syndrome, American Journal on Mental Retardation, 101, 400-412.

Wisniewski, H., Silverman, W., & Weigiel, J. (1994). Ageing, Alzheimer disease and mental retardation. Journal of Intellectual Disability Research, 38, 233-239.

Zigman, W., Schupf, N., Haverman, M., & Silverman, W. (1995). Epidemiology of Alzheimer Disease in mental retardation: Results and recommendations for an international conference. Washington, DC: AAMR.

For further information contact:

Dr. Kate Haller
Developmental Disabilities Center, Morristown Memorial Hospital
Box 60, 100 Madison Avenue
Morristown, NJ 07962