Close
14th February 2025
Presentation and diagnosis of dementia
As well as hearing the patient’s own account, a collateral history is essential. Timeline is important: gradual onset points to a degenerative cause whereas sudden onset points to vascular or other acute causes.
Cognitive symptoms may include deficits in memory, attention or language, e.g. word-finding difficulties. Functional symptoms are generally described as a reduced ability to carry out activities of daily living (ADL).
Differential diagnosis
There is a wide differential diagnosis in dementia. This includes medical conditions that affect organs or systems other than the brain, sometimes referred to as organic causes. This is a misnomer originating in mind-body dualism, as clearly the brain is an organ.
Over 10% of dementia presentations are caused by reversible conditions; a careful approach to history, physical examination and investigations is essential to look for these. In particular, acute or subacute presentation (days to months) should raise suspicion for medical conditions originating outside the brain, including:
- Infection: neurosyphilis, tuberculous meningitis, HSV encephalitis, Lyme disease, CJD
- Inflammation: multiple sclerosis, systemic lupus erythematosus, sarcoidosis, Sjögren’s, limbic encephalitis
- Endocrine: thyroid, pituitary disease, parathyroid disease, Cushing’s
- Metabolic and nutritional: B12 or folate deficiency, uraemia, Wilson’s disease, porphyria
- Traumatic: subdural haematoma, traumatic brain injury
- Toxicity: alcohol, heavy metals, carbon monoxide sequelae, lithium
- Iatrogenic
Neurological and psychiatric differentials include:
- Alzheimer’s disease, vascular dementia, dementia with Lewy bodies, frontotemporal dementia, Korsakoff’s
- Pseudodementia: cognitive and functional deficit due to mental illness such as depression or schizophrenia
- Delirium
- Stroke, normal pressure hydrocephalus (classic triad is urinary incontinence, gait and cognitive disturbance)
Common neuropsychiatric causes of dementia
The dementia subtypes below are common and ordered by prevalence. Mixed dementia refers to dementia caused by two or more underlying aetiologies.
| History features | Examination features | |
|---|---|---|
| Alzheimer’s disease | Memory loss (short-term memory first)
Disorientation to time and place Aphasia (word-finding difficulties) Social withdrawal Risk factors: cardiovascular, Down’s syndrome, FHx family history |
Unremarkable in early stages
Late disease: slow, shuffling gait and stooped posture (similar to Parkinsonian features) Mental state: anxiety, paranoia |
| Vascular dementia | Stepwise cognitive decline, or gradual decline after vascular event, e.g. stroke
Executive function and attention deficits, apathy, disinhibition Cardiovascular risk factors: stroke, HTN, diabetes, coronary artery disease, AF, smoking, obesity etc. |
Transient neurological symptoms: hemiparesis, aphasia, visual field deficits, gait abnormalities
Cardiovascular findings, e.g. arrhythmia, hypertension Mental state: labile mood |
| Dementia with Lewy bodies (DLB) | Fluctuation in cognition, attention, arousal and speech
Visual hallucinations, typically people or animals Mood disturbance: anxiety, depression Autonomic disturbance: orthostatic hypotension, syncope, falls, urinary incontinence, constipation REM sleep disorder, e.g. vivid dreams, restless legs syndrome |
Onset of Parkinsonian symptoms (tremor, rigidity, bradykinesia) simultaneous with or after the cognitive decline
Note that rigidity and bradykinesia can be seen in later-stage Alzheimer’s dementia |
| Frontotemporal dementia (FTD) | Earlier age of onset, average 45-65 years
Memory deficit, disorientation and apraxia Behavioural and personality changes: social disinhibition, inappropriateness, impulsivity, apathy, withdrawal Progressive self-neglect and social withdrawal, including occupation Family history of FTD |
Language fluency deficit, although the most common cause of this presentation is Alzheimer’s |
| Wernicke- Korsakoff syndrome |
Significant alcohol history with poor nutrition
Medical conditions that can impact nutrition: GI surgery, cancer, recurrent vomiting or diarrhoea |
Ataxia, nystagmus
Lateral gaze palsy Vestibulo-ocular reflex impaired |
Table 3 Common causes of dementia with key features of the history and examination
Complete Guide to Clinical Genetics ST3 Application and Recruitment (2027)
Written by Medibuddy. Last updated: October 2026. Clinical Genetics is
Complete Guide to Clinical Radiology ST3 Application and Recruitment (2027)
Recruitment paused: NHS England is not running Clinical Radiology ST3+ recru
Complete Guide to Paediatric Surgery ST3 Application and Recruitment in United Kingdom (2026)
Written by Medibuddy. Last updated: October 2026. If you’re planning
Take your subscriptions with you
Our mobile app allows you to access your interview and exam question banks wherever you are.
