Theme
Neurocognitive Disorders
Neurocognitive disorders encompass a group of conditions in which cognitive functioning is significantly impaired compared to a prior level of performance. They range from the relatively subtle deficits of Mild Neurocognitive Disorder to the profound loss of independence seen in Major Neurocognitive Disorder — what was previously called dementia.
Progressive
Neurocognitive disorders worsen over time. Unlike delirium, they are not acute or self-resolving.
Compared to prior level
Diagnosis requires a measurable decline from the individual's own previous baseline — not a comparison to population norms.
01, The spectrum
Mild, Major & Delirium.
The DSM-5 organises neurocognitive conditions across a spectrum of severity. Delirium stands apart — it is acute, fluctuating, and often reversible.
Mild Neurocognitive Disorder
Modest cognitive decline from a prior level that does not interfere significantly with daily independence. Replaces the older term "mild cognitive impairment." Around 10–15% of cases progress to MaND per year.
Major Neurocognitive Disorder
Significant cognitive decline in one or more domains (memory, executive function, language, etc.) that interferes with independence in everyday activities. The DSM-5 replacement for "dementia."
Delirium
An acute, fluctuating disturbance of attention and awareness caused by an underlying medical condition, substance intoxication or withdrawal, or medication. Distinguished from dementia by its sudden onset and fluctuating course.
02, Major types
The major neurocognitive disorders.
Each disorder has a distinct profile of onset, pathology, and affected brain regions. Click a card to expand details.
Early clinical features
Gradual episodic memory loss
Stepwise decline
REM sleep behaviour disorder
Personality change
Motor symptoms
Key figures
Arnold Pick
1851–1924Czech neurologist who described cases of progressive dementia associated with focal atrophy of the frontal and temporal lobes — now known as frontotemporal dementia, or "Pick's disease" in its classical form. His work established that different anatomical patterns of neurodegeneration could produce distinct clinical syndromes.
Emil Kraepelin
1856–1926German psychiatrist who coined the term "Alzheimer's disease" in the 1910 edition of his psychiatry textbook, bringing Alzheimer's case descriptions to wide clinical attention. Kraepelin's systematic approach to classifying psychiatric disorders laid the groundwork for modern diagnostic systems.
Alois Alzheimer
1864–1915German psychiatrist and neuropathologist who in 1906 described the first documented case of the disease that bears his name — a 51-year-old woman (Auguste Deter) with progressive memory loss, language problems, and behavioural changes. Post-mortem examination revealed the plaques and tangles now recognised as hallmarks of Alzheimer's disease.
Friedrich Heinrich Lewy
1885–1950German-American neurologist who discovered the intracellular protein inclusions (Lewy bodies) found in Parkinson's disease while working in Alois Alzheimer's laboratory in 1912. Lewy bodies were later found to be the defining pathology of Dementia with Lewy Bodies, a major dementia subtype.
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