Differential diagnosis​

Determining the causes of cognitive impairment

A helpful approach to determining the differential diagnosis of cognitive impairment or dementia is the P.I.E.C.E.S.* checklist. It was developed in Ontario as a provincial training strategy to enhance the ability of long-term care facility staff to meet the care requirements of individuals with complex physical and cognitive or mental health needs with associated behavioural issues. P.I.E.C.E.S. stands for:

Physical

Intellectual

Emotional

Capabilities

Environment

Social

Cognitive impairment can be the result of a physical (P) or medical cause, or another intellectual (I) or emotional (E) disorder. The cognitive impairment or disorder, in turn, can be affected positively or negatively by the match between the capabilities (C) of the person and the demands being put on the person, along with the person's environmental (E) and social (S) context and life course.

Primary care providers should use the P.I.E.C.E.S. checklist to determine the diagnosis and differential diagnosis, as well as to identify comorbid conditions that may be affecting the quality of life of the person with cognitive impairment or dementia.

Physical: Think delirium

• Delirium is common in hospitalized elderly undergoing surgery or acute medical illness.
• Individuals with dementia are at high risk for developing dementia with delirium.
• Sudden onset of cognitive decline may be associated with changes in level of consciousness.
• Delirium may fluctuate over the course of the day or several days.
• It is critical to differentiate delirium from a dementia or a superimposed delirium on top of a dementia (one of the major vulnerability factors for delirium is cognitive impairment or dementia).

See: An algorithm to detect and determine the cause of delirium.

Intellectual: Think normal aging and mild cognitive impairment

Consider several other conditions in the differential diagnosis of dementia in older adults.

Normal cognitive changes with age

• Aging typically involves slowing of cognitive processes with normal cognitive testing and no functional impairment.

Mild cognitive impairment (MCI)

• MCI is an impairment in memory or other cognitive processes to an extent greater than that associated with normal aging.
• Cognitive testing shows decline
• The individual does not have functional impairment or dementia.
• There is a high risk for developing dementia. Of people with MCI, 13 per cent develop dementia per year.
• No treatments are currently available to prevent progression from MCI to dementia. Identify, monitor and treat risk factors and complete serial cognitive testing.

Emotional: Think depression or other psychiatric disorder

Depression may present with cognitive changes, also known as "pseudodementia":

• Performance on cognitive testing varies. People often give "I don't know" answers rather than answering incorrectly.
• If depression is suspected, consider supportive tools such as the Geriatric Depression Scale and the Cornell Depression Scale.
• Late-life onset of depression may be associated with increased risk for dementia.

Differentiating the types of dementia

Although there are many pathophysiological processes that lead to dementia in older adults, distinguishing between different dementias is important. In considering the differential diagnosis of dementia, distinguishing among several features may be helpful. (see Table 10.1 Characteristic features of common types of dementia). These features may help to determine the cause of the dementia while informing prognosis and management.

Common types of dementias

Alzheimer's dementia

• Most common dementia, accounting for 50 to 60 per cent of all cases
• Characteristic gradual onset with progressive decline

Dementia with Lewy bodies

• Second most common type of dementia
• Associated with visual hallucinations, Parkinsonian motor symptoms, marked fluctuation in cognition or level of consciousness, sensitivity to extrapyramidal side-effects of antipsychotic medication

Vascular cognitive impairment and vascular dementia

• May be caused by a single large stroke or accumulation of multiple subcortical strokes
• Often associated with Alzheimer's dementia (mixed dementia)
• 30 per cent of people with a stroke progress to dementia

Frontotemporal dementia

• Early loss of social skills, disinhibited behaviours, apathy and loss of insight
• Often has earlier onset than other dementias and is frequently associated with family history of frontotemporal dementia