Neurology Neurology · Geriatrics

Dementia Causes

Dementia is a syndrome of acquired cognitive decline. Knowing the reversible causes prevents missing treatable diagnoses, and distinguishing the common types guides management.

✦ The Mnemonic

"DEMENTIA Finds Causes"

Degenerative · Endocrine/metabolic · Medications · Emotional · Nutrition · Toxins · Infection · Arterial

Alz Alzheimer's disease Most common (60–70%); progressive; amyloid plaques + tau tangles; memory onset; ACEi reduce symptoms

VD Vascular dementia Second most common; stepwise decline; white matter disease; cardiovascular risk factors

DLB Dementia with Lewy bodies Fluctuating cognition, visual hallucinations, Parkinsonism; REM sleep behaviour disorder; avoid antipsychotics

FTD Frontotemporal dementia Young onset (<65); personality/behavioural change first; memory relatively preserved initially

Rev Reversible causes Hypothyroidism, B12 deficiency, depression ('pseudodementia'), normal pressure hydrocephalus, SDH, neurosyphilis

📚 Clinical Breakdown

Alzheimer's disease: the cholinergic hypothesis — loss of cholinergic neurons in the basal nucleus of Meynert drives memory impairment. Acetylcholinesterase inhibitors (donepezil, rivastigmine, galantamine) are symptomatic treatments for mild-moderate AD. Memantine (NMDA antagonist) is used for moderate-severe AD.

Normal pressure hydrocephalus (NPH): the triad of wacky, wobbly, wet — dementia, gait apraxia (broad-based, magnetic gait), and urinary incontinence. CT/MRI shows dilated ventricles out of proportion to cortical atrophy. Treatment: ventriculoperitoneal (VP) shunt — can be dramatically effective.

Dementia with Lewy bodies: extreme sensitivity to antipsychotics (can cause severe Parkinsonism and neuroleptic malignant syndrome) — avoid haloperidol and other conventional antipsychotics. Use atypical antipsychotics with extreme caution if needed for hallucinations. Rivastigmine is licensed for DLB.

Most common dementia Alzheimer's disease (60–70%)

DLB — avoid Conventional antipsychotics

Reversible cause — always check Thyroid function + B12 + syphilis serology

NPH triad Wacky, Wobbly, Wet

⭐ Clinical Pearl

MMSE vs MoCA: the Montreal Cognitive Assessment (MoCA) is more sensitive than the MMSE for mild cognitive impairment and early dementia — particularly for executive function and visuospatial abilities. Use MoCA as a first-line screening tool; a score of <26/30 indicates possible cognitive impairment.

← Brainstem Lesions Next: Seizure Causes →