Medicine – Dementia

Dementia is an acquired syndrome of progressive decline in cognitive function severe enough to interfere with normal daily life and independence. It commonly affects memory, executive function, language, visuospatial ability, judgment, behaviour, and personality.

The older description of “global impairment of intellect, memory and personality” captures the general concept, but modern practice usually describes dementia in terms of decline across one or more cognitive domains rather than using the term “intellect” alone.

1. Core Features

A patient with dementia may develop problems with:

Memory.

Language.

Planning and organisation.

Judgment.

Orientation.

Recognition.

Behaviour.

Personality.

The decline is acquired, meaning that it represents deterioration from a previous level of functioning.

2. Dementia versus Delirium

Dementia usually develops gradually over months or years.

Delirium, in contrast, develops acutely over hours to days and is characterised by:

Fluctuating attention.

Altered awareness.

Disorganised thinking.

A patient with dementia can also develop delirium on top of the chronic cognitive impairment.

3. Causes of Dementia

The causes can broadly be divided into:

Potentially reversible or treatable causes.

and

Usually progressive neurodegenerative or vascular causes.

This distinction is clinically important because potentially treatable conditions should be actively sought.

4. Vitamin B12 Deficiency

Vitamin B12 deficiency is an important potentially treatable cause of cognitive impairment.

It may also produce:

Peripheral neuropathy.

Loss of vibration and proprioception.

Sensory ataxia.

Subacute combined degeneration of the spinal cord.

Macrocytic anaemia.

However, neurological B12 deficiency can occur even without obvious anaemia.

5. Folate Deficiency

Folate deficiency can be associated with:

Macrocytic anaemia.

Fatigue.

Cognitive symptoms.

However, isolated folate deficiency is a less classic cause of a dementia syndrome than vitamin B12 deficiency.

An important caution is that treating folate deficiency without recognising coexisting B12 deficiency can correct the anaemia while neurological injury from B12 deficiency continues.

6. Hypothyroidism

Hypothyroidism can produce:

Cognitive slowing.

Poor concentration.

Memory impairment.

Depression.

Fatigue.

Because it may mimic dementia, thyroid function testing is commonly included in the investigation of cognitive decline.

7. Normal Pressure Hydrocephalus

Normal pressure hydrocephalus is an important potentially treatable cause.

The classic triad is:

Gait disturbance.

Cognitive impairment.

Urinary dysfunction.

The gait is often:

Magnetic, with the feet appearing “glued to the floor.”

Brain imaging shows:

Ventriculomegaly disproportionate to cortical atrophy.

Selected patients may improve after:

Ventriculoperitoneal shunting.

8. Chronic Subdural Haematoma

A chronic subdural haematoma can cause slowly progressive cognitive impairment, especially in older adults.

It may follow relatively minor head trauma and can present with:

Confusion.

Personality change.

Drowsiness.

Headache.

Focal neurological deficits.

Because it is potentially treatable, neuroimaging is important when the presentation is atypical or when there is a relevant history.

9. Syphilis

Neurosyphilis can cause cognitive and behavioural abnormalities.

Possible features include:

Memory loss.

Personality change.

Psychiatric symptoms.

Sensory abnormalities.

Pupillary abnormalities.

It is uncommon in many settings but remains an important potentially treatable diagnosis in selected patients.

10. HIV-Associated Cognitive Disease

HIV can affect cognition directly and can also predispose to multiple CNS infections and malignancies.

HIV-associated neurocognitive disorders can produce:

Psychomotor slowing.

Poor concentration.

Memory difficulty.

Executive dysfunction.

In advanced immunosuppression, opportunistic infections must also be considered.

11. Other Treatable or Reversible Contributors

Other important reversible or partly reversible causes of cognitive impairment include:

Medication effects.

Depression.

Electrolyte abnormalities.

Severe liver or renal disease.

Sleep disorders.

Alcohol or sedative toxicity.

Therefore, not every patient with cognitive symptoms has a primary neurodegenerative dementia.

12. Alzheimer’s Disease

Alzheimer’s disease is the most common progressive cause of dementia.

It typically begins with:

Progressive recent memory loss.

Later, patients develop:

Language impairment.

Disorientation.

Executive dysfunction.

Behavioural change.

The classic pathology is:

Beta-amyloid plaques + tau neurofibrillary tangles + hippocampal degeneration.

13. Vascular Dementia

The older term multi-infarct dementia is now more commonly included under:

Vascular dementia or vascular cognitive impairment.

It results from cerebrovascular disease.

This may be caused by:

Multiple cortical infarcts.

Small-vessel disease.

Strategic single infarcts.

Chronic cerebral ischaemic injury.

14. Clinical Pattern of Vascular Dementia

Vascular dementia may show:

Stepwise deterioration.

Focal neurological signs.

Gait disturbance.

Executive dysfunction.

However, progression is not always classically stepwise.

Patients may also have mixed pathology, particularly:

Alzheimer disease + vascular disease.

15. Chronic Alcohol Use

Chronic heavy alcohol use can contribute to cognitive impairment through several mechanisms.

These include:

Direct neurotoxicity.

Thiamine deficiency.

Malnutrition.

Liver disease.

Repeated head injury.

Wernicke-Korsakoff syndrome.

Therefore, alcohol-related cognitive impairment is often multifactorial.

16. Korsakoff Syndrome

Korsakoff syndrome is particularly associated with chronic thiamine deficiency.

The key features are:

Severe anterograde amnesia.

Variable retrograde amnesia.

Confabulation.

Poor insight.

It is better regarded as a specific chronic amnestic syndrome rather than simply a typical diffuse dementia.

17. Parkinson Disease Dementia

Parkinson disease can eventually be associated with dementia.

Typical cognitive problems include:

Executive dysfunction.

Visuospatial impairment.

Attention problems.

Memory impairment.

The timing of dementia relative to parkinsonism is important when distinguishing Parkinson disease dementia from dementia with Lewy bodies.

18. Dementia with Lewy Bodies

The original note groups Parkinson disease with “Lewy body dementia,” but these are related rather than identical diagnoses.

Dementia with Lewy bodies (DLB) is characterised by:

Progressive cognitive decline.

Fluctuating cognition.

Recurrent visual hallucinations.

REM sleep behaviour disorder.

Spontaneous parkinsonism.

19. DLB versus Parkinson Disease Dementia

A useful clinical distinction is the timing of cognitive impairment.

If dementia develops:

Before or within about 1 year of parkinsonism → think dementia with Lewy bodies.

If established Parkinson disease is present for more than about 1 year before dementia develops:

Think Parkinson disease dementia.

This “1-year rule” is a clinical convention.

20. Frontotemporal Dementia

The older term Pick’s disease is now usually placed within the broader group:

Frontotemporal dementia, FTD.

FTD commonly presents with early changes in:

Personality.

Behaviour.

Social conduct.

Language.

Memory may be relatively less affected early compared with Alzheimer disease.

21. Behavioural Variant Frontotemporal Dementia

Behavioural-variant FTD may produce:

Disinhibition.

Apathy.

Loss of empathy.

Compulsive behaviour.

Dietary change.

Executive dysfunction.

This pattern reflects predominant frontal-lobe dysfunction.

22. Primary Progressive Aphasia

Some frontotemporal degeneration syndromes present primarily with:

Progressive language impairment.

These are grouped under:

Primary progressive aphasia.

Different subtypes affect speech production, word meaning, or word retrieval differently.

23. Huntington Disease

Huntington disease is an autosomal dominant neurodegenerative disorder caused by a:

CAG repeat expansion in the HTT gene.

The classic triad includes:

Chorea.

Psychiatric disturbance.

Cognitive decline.

Executive dysfunction and personality changes may precede severe global dementia.

24. Chronic Head Injury

Repeated significant head trauma can contribute to chronic neurodegeneration.

One recognised disorder is:

Chronic traumatic encephalopathy.

Potential features include:

Behavioural change.

Mood disturbance.

Cognitive decline.

Motor abnormalities.

However, diagnosis during life can be difficult and remains an area of active research.

25. Creutzfeldt–Jakob Disease

CJD is a rare prion disease causing rapidly progressive dementia.

Important associated features include:

Myoclonus.

Ataxia.

Behavioural changes.

Visual abnormalities.

Unlike most dementias, progression is usually extremely rapid, often over months.

26. Rapidly Progressive Dementia

If dementia develops over weeks or a few months rather than years, consider:

CJD.

Autoimmune encephalitis.

Infectious encephalitis.

Malignancy.

Toxic or metabolic disease.

Vasculitis.

This is important because several causes of rapidly progressive dementia are treatable.

27. Assessment of a Patient with Dementia

Evaluation should include:

History from the patient.

Collateral history from family or carers.

Cognitive assessment.

Neurological examination.

Medication review.

Assessment of daily functioning.

Investigation for reversible causes.

28. Cognitive Testing

Useful screening tools include:

MMSE.

MoCA.

These assess domains such as:

Memory.

Attention.

Language.

Executive function.

Visuospatial ability.

A screening score should always be interpreted in the clinical context.

29. Laboratory Investigation

Common investigations may include:

Full blood count.

Vitamin B12.

Folate where appropriate.

Thyroid function.

Electrolytes.

Renal function.

Liver function.

Further testing for HIV, syphilis, or other conditions depends on the clinical context.

30. Neuroimaging

CT or MRI brain helps identify:

Cerebral atrophy.

Vascular disease.

Normal pressure hydrocephalus.

Subdural haematoma.

Tumours.

Previous infarction.

MRI provides greater anatomical detail in many situations.

31. Potentially Treatable Causes – Note Form

Vitamin B12 deficiency.

Hypothyroidism.

Normal pressure hydrocephalus.

Chronic subdural haematoma.

Syphilis.

HIV-associated disease.

Medication toxicity.

Depression.

Metabolic abnormalities.

Folate deficiency may contribute to cognitive impairment but is a less classic isolated reversible dementia cause than B12 deficiency.

32. Usually Progressive Causes – Note Form

Alzheimer’s disease.

Vascular dementia.

Dementia with Lewy bodies.

Parkinson disease dementia.

Frontotemporal dementia.

Huntington disease.

Alcohol-related neurocognitive disease.

Chronic traumatic encephalopathy.

Creutzfeldt–Jakob disease.

33. Alzheimer’s Disease – Pattern

Prominent early episodic memory loss.

Gradual progression over years.

Later language, orientation and functional decline.

Hippocampal/medial temporal atrophy.

34. Vascular Dementia – Pattern

History of vascular risk or stroke.

Executive dysfunction.

Focal neurological signs may be present.

Gait disturbance common.

Progression may be stepwise or gradual.

35. Lewy Body Dementia – Pattern

Fluctuating cognition.

Recurrent visual hallucinations.

REM sleep behaviour disorder.

Parkinsonism.

This combination is particularly high yield.

36. Frontotemporal Dementia – Pattern

Early personality or behavioural change.

or

Progressive language dysfunction.

Memory may initially be less prominent than in Alzheimer disease.

37. Normal Pressure Hydrocephalus – Pattern

Magnetic gait.

Cognitive impairment.

Urinary urgency/incontinence.

Ventriculomegaly.

This is important because selected patients may improve with shunting.

38. CJD – Pattern

Very rapid cognitive decline.

Myoclonus.

Ataxia.

Progression over months.

Think of CJD when dementia progresses much faster than typical Alzheimer disease.

Key Clinical Pattern

The first important question in dementia is:

COULD THIS BE TREATABLE?

Think of:

B12 deficiency + hypothyroidism + NPH + chronic subdural haematoma + infection + medication/metabolic causes.

Then consider the major progressive patterns:

Alzheimer = memory first.

Vascular = vascular history + executive/gait/focal signs.

Lewy body = fluctuations + visual hallucinations + REM sleep behaviour disorder + parkinsonism.

Frontotemporal = behaviour or language first.

Huntington = chorea + psychiatric symptoms + cognitive decline.

CJD = rapidly progressive dementia + myoclonus + ataxia.