Dementia and Cognitive Impairment

Dementia and Cognitive Impairment

Dementia and Cognitive Impairment

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Definitions & Overview - Mind Fades

  • Dementia: Chronic, progressive, global cognitive decline; consciousness clear; ADLs impaired.
  • Delirium: Acute, fluctuating attention deficit; altered consciousness; ADLs often impaired. 📌 I WATCH DEATH (Infection, Withdrawal, Acute metabolic, Trauma, CNS pathology, Hypoxia, Deficiencies, Endocrinopathies, Acute vascular, Toxins/drugs, Heavy metals).
  • Mild Cognitive Impairment (MCI): Cognitive decline greater than normal for age/education; ADLs intact; not dementia.
  • Key Differentiating Features:
FeatureDementiaDeliriumMCI
OnsetInsidiousAcuteInsidious
CourseProgressiveFluctuatingStable/Progressive
ConsciousnessClearAlteredClear
AttentionNormal initiallyImpairedNormal
ADLsImpairedOften ImpairedIntact
FeatureAlzheimer's Disease (AD)Vascular Dementia (VaD)Lewy Body Dementia (LBD)Frontotemporal Dementia (FTD) (Pick's Disease)
OnsetInsidious, gradualVariable (sudden/stepwise/gradual)GradualGradual, often < 65 yrs
CourseProgressiveStepwise or progressiveFluctuating, progressiveProgressive
Key Cognitive DeficitsAmnesia (early), aphasia, apraxia, agnosiaExecutive dysfunction, focal deficits (site-dependent)Fluctuating attention, visual hallucinations, visuospatial impairmentBehavioural (disinhibition, apathy) or language variants (e.g., PPA)
Motor FeaturesMinimal early; late rigidityFocal neurological signs, gait issuesParkinsonism (often early, symmetric), REM sleep behaviour disorder (RBD)+/- Parkinsonism, MND signs (some variants)
Pathology/Signsβ-amyloid plaques, Tau neurofibrillary tanglesCerebrovascular lesions (infarcts, lacunes, white matter)α-synuclein Lewy bodies (cortical/subcortical), Lewy neurites. 📌 LBD: Fluctuations, Hallucinations (visual), ParkinsonismTau (Pick bodies) or TDP-43 inclusions; marked frontal/temporal atrophy

Clinical Approach & Workup - The Cognitive Quest

  • History: Collateral history is crucial. Obtain from family/caregivers.
  • Neurological Exam: Key elements: focal deficits, gait changes, primitive reflexes.
  • Cognitive Screening Tools:
    • MMSE: Score < 24/30 suggests impairment.
    • MoCA: Score < 26/30; more sensitive for Mild Cognitive Impairment (MCI).
    • Clock Drawing Test (CDT): Assesses visuospatial and executive functions.
  • Laboratory Workup (for reversible causes): Thyroid function (TSH), Vitamin B12, CBC, CMP.
    • 📌 Mnemonic for reversible causes: DEMENTIAS (Drugs, Emotional disorders, Metabolic, Endocrine, Nutritional, Trauma, Infection, Alcohol/Arteriosclerosis, Subdural hematoma).
  • Neuroimaging:
    • CT/MRI: Indications: acute onset, age <60, focal neurological signs, suspected NPH. Typical AD: hippocampal atrophy.
    • PET: Role in differentiating dementias (FDG-PET for metabolic patterns); amyloid/tau PET for specific proteinopathies.

⭐ CSF analysis for ↓ amyloid beta 42 (A$\beta$42) and ↑ tau protein (total & phosphorylated) can support Alzheimer's Disease (AD) diagnosis, particularly in atypical presentations.

Management Strategies - Navigating the Maze

  • Non-Pharmacological Interventions (First-line):

    • Cognitive stimulation, regular physical activity.
    • Environmental modifications (e.g., safety, orientation aids).
    • Caregiver education and strong support.
  • Pharmacological Treatment:

    Drug ClassExamplesPrimary IndicationCommon DosesKey Side Effects
    Cholinesterase InhibitorsDonepezil, Rivastigmine, GalantamineMild-Moderate AD, LBDDonepezil: 5-10 mg/day; Rivastigmine: 3-12 mg/day; Galantamine: 8-24 mg/dayGI upset (nausea, diarrhea), bradycardia, insomnia
    NMDA Receptor AntagonistMemantineModerate-Severe AD (adjunct or mono)Start 5 mg/day, target 20 mg/day (10 mg BID)Dizziness, headache, confusion, agitation, constipation
  • Behavioral & Psychological Symptoms of Dementia (BPSD):

    • Non-pharmacological strategies first.
    • Judicious psychotropics for severe/refractory symptoms.

⭐ Cholinesterase inhibitors often show better efficacy in Lewy Body Dementia (LBD) for cognitive and neuropsychiatric symptoms than in Frontotemporal Dementia (FTD).

High‑Yield Points - ⚡ Biggest Takeaways

  • Alzheimer's Disease (AD): Most common; amyloid plaques, tau tangles, progressive memory loss.
  • Vascular Dementia: Stepwise decline in cognition; associated with CVD risk factors and stroke history.
  • Lewy Body Dementia (LBD): Visual hallucinations, parkinsonism, fluctuating cognition; REM sleep behavior disorder is a key early sign.
  • Frontotemporal Dementia (FTD): Early personality changes, disinhibition, or progressive aphasia.
  • Always rule out reversible causes: B12 deficiency, hypothyroidism, Normal Pressure Hydrocephalus.
  • MMSE < 24 suggests impairment; cholinesterase inhibitors (e.g., Donepezil) are used for AD treatment.

Practice Questions: Dementia and Cognitive Impairment

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Reversible dementia causes are all except-

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_____ delirium is commonly associated with hepatic and renal encephalopathies.

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_____ delirium is commonly associated with hepatic and renal encephalopathies.

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