All forms of dementia — Alzheimer’s disease included — share overarching diagnostic criteria. According to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), a diagnosis of dementia (which they classify as a “major neurocognitive disorder”) requires meeting the following criteria (using a person’s medical history and cognitive assessment):
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An impairment in one or more cognitive domains (e.g., executive function, language, memory.)
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A decline in cognitive ability compared with past levels of functioning
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An impairment in the ability to function independently in daily life
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Symptoms not occurring as a result of delirium
In addition to a dementia diagnosis, conclusively determining whether a person has Alzheimer’s disease requires an autopsy to see if amyloid plaques are present in the brain. This limits diagnosis to after death, which is not ideal. To help diagnose a person while still alive, other types of dementia can be ruled out, thereby increasing the likelihood that Alzheimer’s disease is present. As a result, Alzheimer’s has been referred to as a “disease of exclusion”.
Some other common types of dementia are Lewy body dementia, vascular dementia, and frontotemporal (frontal and temporal lobe) dementia. In general, they vary somewhat in their presentation.
| Type | Pathology | Percentage of all dementia | Characteristics |
|---|---|---|---|
| Alzheimer’s disease | Amyloid plaques and neurofibrillary tangles in the brain | 60–80% | Gradual onset, Progressive course, Multiple cognitive deficits, including memory impairment |
| Vascular dementia | Marker of cardiovascular disease (CVD) event (stroke, blockage in arteries) | 20% | Abrupt onset, fluctuating course, history of CVD event, focal deficits (abnormal gait, muscle weakness, etc.) |
| Lewy body dementia | Alpha-synuclein aggregates in the brain | 5–15% | Fluctuations in cognition, hallucinations, difficulty walking |
| Frontotemporal dementia | Degeneration of frontal and temporal lobes | 3% (people >65 years old) and 10% (people <65 years old) | Difficulty with language (aphasia), executive dysfunction, visuospatial function usually unaffected |
References
- ^Weller J, Budson ACurrent understanding of Alzheimer's disease diagnosis and treatment.F1000Res.(2018)
- ^Silvia Duong, Tejal Patel, Feng ChangDementia: What pharmacists need to knowCan Pharm J (Ott).(2017 Feb 7)
- ^David B Hogan, Nathalie Jetté, Kirsten M Fiest, Jodie I Roberts, Dawn Pearson, Eric E Smith, Pamela Roach, Andrew Kirk, Tamara Pringsheim, Colleen J MaxwellThe Prevalence and Incidence of Frontotemporal Dementia: a Systematic ReviewCan J Neurol Sci.(2016 Apr)
- ^Tripathi M, Vibha DReversible dementias.Indian J Psychiatry.(2009-Jan)
- ^Schilling LP, Zimmer ER, Shin M, Leuzy A, Pascoal TA, Benedet AL, Borelli WV, Palmini A, Gauthier S, Rosa-Neto PImaging Alzheimer's disease pathophysiology with PET.Dement Neuropsychol.(2016)