Early Diagnosis of Dementia

American Family Physician,  Feb 15, 2001  by Karen S. Santacruz,  Daniel Swagerty

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Until recently, the most significant issue facing a family physician regarding the diagnosis and treatment of dementia was ruling out delirium and potentially treatable etiologies. However, as more treatment options become available, it will become increasingly important to diagnose dementia early. Dementia may be suspected if memory deficits are exhibited during the medical history and physical examination. Information from the patient's family members, friends and caregivers may also point to signs of dementia. Distinguishing among age-related cognitive decline, mild cognitive impairment and Alzheimer's disease may be difficult and requires evaluation of cognitive and functional status. Careful medical evaluation to exclude treatable causes of cognitive impairment is important. Patients with early dementia may benefit from formal neuropsychologic testing to aid in medical and social decision-making. Follow-up by the patient's family physician is appropriate in most patients. However, a subspecialist may be helpful in the diagnosis and management of patients with dementia with an unusual presentation or following an atypical course. (Am Fam Physician 2001; 63:703-13,717-8.)

The prevalence of dementia is expected to increase dramatically in future years as life expectancy continues to increase and the baby-boomer population ages. The cumulative incidence of Alzheimer's disease has been estimated to be as high as 4.7 percent by age 70, 18.2 percent by age 80 and 49.6 percent by age 90.(1) Proposed risk factors for dementia include a family history of dementia, previous head injury, lower educational level and female sex.(2) Alzheimer's disease is the most common cause of dementia; many of the remaining cases of dementia are caused by vascular disease and Lewy body disease. Vascular disease and Lewy body disease often occur in combination with Alzheimer's disease.(3,4)

Clinical Presentation

A practical approach to the diagnosis of dementia begins with the clinical recognition of a progressive decline in memory, a decrease in the patient's ability to perform activities of daily living, psychiatric problems, personality changes and problem behaviors (Table 1).(5) While the clinical presentation of dementia may vary, depending on the etiology, the diagnostic features are constant. They are well described in the Diagnostic and Statistical Manual of Mental Disorders, 4th ed. (DSM-IV) and summarized in Table 2.(6)

HISTORY

The early diagnosis of dementia requires careful questioning to elicit clues to the presence of functional and cognitive impairment (Table 3).(5) Interviewing friends as well as family members is helpful, because family members may have adopted coping strategies to help the patient with dementia, which sometimes conceal the patient's impairment, making early diagnosis difficult. For example, a caregiver may take on additional responsibilities such as shopping and financial management, possibly masking the patient's level of impairment.

During the medical history-taking, questions should be asked about forgetfulness and orientation. Inquiries should also be made regarding activities of daily living, including instrumental activities such as everyday problem solving and handling of business and financial affairs. Independent functioning in community affairs, such as job responsibilities, shopping and participation in volunteer and social groups, should be assessed. Evidence of problems with home activities, hobbies and personal care should also be sought. In the early stages of dementia, the patient may show restricted interest in hobbies and other activities, and may require prompting to maintain personal hygiene.(7)

A variety of rating scales are available for evaluating cognitive function. Their use may or may not be required in the evaluation of early dementia.

PHYSICAL EXAMINATION AND COGNITIVE TESTING

The findings of the physical examination may suggest an etiology for dementia. For example, dementia resulting from vascular disease may be accompanied by focal neurologic findings.

Physical examination should include assessment of cognitive domains, including speech (aphasia), motor memory (apraxia), sensory recognition (agnosia) and complex behavior sequencing (executive functioning). Aphasia may be detected by asking the patient to name body parts or objects in the room. Frequent use of vague terms such as "thing" and "it" may also signify deterioration of language function. An example of a test for apraxia is to ask the patient to pantomime the use of a common object such as a hammer or a toothbrush. Agnosia can be evaluated by first asking the patient to close his or her eyes and then placing an object, such as a key or a coin, in the patient's hand and asking the patient to identify it without looking at it. Inability to recognize a common object despite normal sensory function signifies agnosia.

Asking the patient to perform a series of simple tasks is a way to evaluate executive functioning. For example, the patient can be asked to put a piece of paper in his or her right hand, fold it in half and put it on the floor. This task would be difficult for a patient with impairment in the ability to plan, initiate, sequence and monitor complex behavior. Asking the patient to perform serial subtraction of 7s (backward from 100 to 65), to spell the word "world" backward and to produce verbal word lists, such as names of animals or items in a grocery store, are other ways to test executive functioning and abstract thinking.