What is the key feature that distinguishes delirium from dementia?

A: Delirium affects memory; dementia primarily affects attention

B: Delirium involves acute onset and fluctuating consciousness; dementia is typically gradual and progressive

C: Delirium is always caused by substance use; dementia has a genetic basis

D: Delirium is irreversible; dementia responds to treatment

Correct: Delirium involves acute onset and fluctuating consciousness; dementia is typically gradual and progressive

Delirium is characterised by acute onset (hours to days), fluctuating course, and a disturbance in attention and awareness — often with perceptual disturbances (hallucinations), disorganised thinking, and altered arousal. It is usually caused by an underlying medical condition, medication, or substance. Dementia (now termed Major Neurocognitive Disorder in DSM-5) typically develops gradually over months to years and does not involve the fluctuating consciousness that characterises delirium. Importantly, delirium in patients with dementia is common and associated with accelerated cognitive decline.

The DSM-5 replaced the term "dementia" with which diagnostic label?

A: Cognitive impairment syndrome

B: Major Neurocognitive Disorder

C: Acquired cognitive disorder

D: Progressive memory disorder

Correct: Major Neurocognitive Disorder

The DSM-5 introduced "Major Neurocognitive Disorder" (MaND) to replace "dementia," and "Mild Neurocognitive Disorder" (MiND) to replace "mild cognitive impairment." The change was intended to be more inclusive (capturing conditions beyond Alzheimer's), to reduce stigma, and to create a framework that spans a continuum from mild to severe cognitive decline. Specific subtypes are identified based on aetiology (e.g., due to Alzheimer's disease, Lewy body disease, vascular disease).

The neuropathological hallmarks of Alzheimer's disease include:

A: Lewy bodies and alpha-synuclein deposits

B: Amyloid-beta plaques and neurofibrillary tangles (tau)

C: TDP-43 protein inclusions and frontal lobe atrophy

D: Prion protein misfolding and spongiform changes

Correct: Amyloid-beta plaques and neurofibrillary tangles (tau)

Alzheimer's disease is characterised neuropathologically by extracellular amyloid-beta (Aβ) plaques and intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein. These pathological changes begin in the entorhinal cortex and hippocampus — explaining the early memory impairment — before spreading to association cortices. The amyloid cascade hypothesis proposes that Aβ accumulation is the initiating event, though the relationship between plaques and symptoms is complex.

Vascular dementia is the second most common form of dementia after Alzheimer's disease.

Answer: True

Vascular dementia (VaD) is the second most common form, accounting for approximately 15–20% of dementia cases, following Alzheimer's (60–70%). VaD results from cerebrovascular disease — including strokes, small vessel disease, and white matter lesions — which disrupt blood flow to the brain. Unlike Alzheimer's, VaD often shows a stepwise rather than gradual decline. Mixed dementia (Alzheimer's + vascular pathology) is increasingly recognised as common, particularly in older adults.

Lewy body dementia is clinically distinguished by which combination of features?

A: Early memory loss, language deficits, and frontal disinhibition

B: Fluctuating cognition, visual hallucinations, and Parkinsonism

C: Stepwise cognitive decline following discrete strokes

D: Personality change, disinhibition, and relative sparing of memory

Correct: Fluctuating cognition, visual hallucinations, and Parkinsonism

Dementia with Lewy bodies (DLB) has three core clinical features: fluctuating cognition with pronounced variations in attention, recurrent complex visual hallucinations (often detailed and vivid), and spontaneous Parkinsonism. REM sleep behaviour disorder is a strong supportive feature. DLB is important to identify because patients have severe sensitivity to antipsychotic medications — even low doses can cause life-threatening reactions — making accurate differential diagnosis essential.

Acetylcholinesterase inhibitors (e.g., donepezil, rivastigmine) are used in Alzheimer's disease because:

A: They clear amyloid plaques from the brain

B: They increase available acetylcholine by inhibiting its breakdown

C: They prevent tau phosphorylation

D: They enhance dopamine transmission in the hippocampus

Correct: They increase available acetylcholine by inhibiting its breakdown

Alzheimer's disease involves significant loss of cholinergic neurons in the basal forebrain (particularly the nucleus basalis of Meynert), leading to reduced acetylcholine in the cortex and hippocampus. Acetylcholinesterase inhibitors prevent the enzymatic breakdown of acetylcholine, thereby increasing its availability at synapses. They produce modest symptomatic improvement in cognition and functioning but do not alter the underlying disease progression. Memantine, an NMDA receptor antagonist, is used in moderate-to-severe Alzheimer's.

Mild Neurocognitive Disorder (mild NCD) always progresses to Major Neurocognitive Disorder (dementia).

Answer: False

Mild NCD (previously "mild cognitive impairment") represents a cognitive decline greater than expected for age but that does not interfere significantly with daily activities. Crucially, it does not inevitably progress to dementia. Annual conversion rates from mild NCD to dementia are approximately 10–15%, but a significant proportion of individuals remain stable or even revert to normal cognitive functioning. Identifying mild NCD is clinically valuable as it may allow early intervention and lifestyle modifications.