Neurodegenerative Diseases

Neurodegenerative Diseases

Neurodegenerative Diseases

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Neurodegenerative Diseases - Brain's Protein Glitches

Definition: Progressive, often age-related, loss of neuron structure and/or function. Common mechanisms:

  • Protein misfolding & aggregation (proteinopathies)
  • Oxidative stress
  • Neuroinflammation
  • Impaired proteostasis

⭐ Most neurodegenerative diseases involve intracellular or extracellular aggregates of misfolded proteins.

Key Proteinopathies & Associated Diseases: Protein aggregates and clearance in neurodegeneration

ProteinDisease ExamplesLocation of Aggregates
Aβ (Amyloid-β)Alzheimer's DiseaseExtracellular plaques
TauAlzheimer's, FTDIntracellular NFTs
α-synucleinParkinson's, MSAIntracellular Lewy bodies
TDP-43ALS, FTDCytoplasmic inclusions
PrP (Prion)CJDPrPSc aggregates (intra/extra)

Neurodegenerative Diseases - Memory's Missing Pages

  • Alzheimer's Disease (AD): Most common dementia.
    • Etiopathogenesis: Extracellular Aβ plaques (from Amyloid Precursor Protein - APP); Intracellular neurofibrillary tangles (NFTs) of hyperphosphorylated Tau protein.
    • Gross: Cortical atrophy (frontal, temporal, parietal lobes), widened sulci, hydrocephalus ex vacuo.
    • Microscopic: Neuritic plaques, NFTs, amyloid angiopathy, neuronal loss. Alzheimer's Brain Changes: Gross and Microscopic
    • Genetic Factors:
      • Early-onset (familial): APP, PSEN1, PSEN2.
      • Late-onset (sporadic):

        APOEε4 is the major genetic risk factor for sporadic AD.

      • 📌 Mnemonic: Old APPs Play Songs 1 & 2 Every 4ever (APP, PSEN1, PSEN2, APOEε4).
    • Association: ↑ risk in Down syndrome (Trisomy 21; APP gene on Chr 21).
    • Clinical: Progressive memory loss, cognitive decline, dementia features develop over years (e.g., disorientation, mood changes).

Neurodegenerative Diseases - Synuclein's Shaky Saga

  • Parkinson's Disease (PD):
    • Pathology: Loss of dopaminergic neurons in substantia nigra pars compacta → ↓ dopamine. Parkinson's disease pathology
    • Hallmark: Intracytoplasmic Lewy bodies (α-synuclein aggregates). Lewy bodies in neurons, H&E and alpha-synuclein stain
    • Clinical: 📌 TRAP mnemonic: Tremor (resting, "pill-rolling"), Rigidity ("cogwheel"), Akinesia/Bradykinesia, Postural instability.

⭐ Lewy bodies containing α-synuclein are the hallmark of Parkinson's disease.

  • Other α-Synucleinopathies:
    • Lewy Body Dementia (LBD): Fluctuating cognition, visual hallucinations (early), Parkinsonism. Lewy bodies in cortex & brainstem.
    • Multiple System Atrophy (MSA): Parkinsonism (poor L-dopa response), autonomic failure (e.g., orthostatic hypotension), cerebellar ataxia. α-synuclein in oligodendroglial cytoplasm (Papp-Lantos bodies).

Neurodegenerative Diseases - Genetic Repeats & Motor Retreats

  • Huntington's Disease (HD): Autosomal Dominant (AD); CAG repeats (HTT gene, Chr 4). >40 repeats = full penetrance; 36-39 = reduced penetrance. Exhibits anticipation.
    • Pathophysiology: Caudate atrophy, ↓GABAergic neurons. 📌 "Hunting for GABA in the Caudate with CAGs".
    • MRI showing caudate atrophy in prodromal Huntington's

⭐ Huntington's disease is caused by a CAG repeat expansion in the huntingtin gene, exhibiting anticipation.

  • Amyotrophic Lateral Sclerosis (ALS): Combined Upper Motor Neuron (UMN) & Lower Motor Neuron (LMN) signs.
    • Pathophysiology: TDP-43 proteinopathy (most common); SOD1 gene mutations (familial cases).
    • Histology: Bunina bodies (characteristic intracytoplasmic inclusions in LMNs).
    • Protein Accumulation in Neurodegenerative Diseases

Neurodegenerative Diseases - Spongy Scare & Frontal Flare

  • Prion Diseases (Spongy Scare):
    • Pathogenesis: Accumulation of abnormal prion protein (PrPSc).
    • Key CNS finding: Spongiform encephalopathy (neuronal loss, gliosis, vacuolation).
    • Creutzfeldt-Jakob Disease (CJD): Rapidly progressive dementia, myoclonus, ataxia, visual disturbances. 📌 Mnemonic: Can't Jog Daily (ataxia, rapid).

    ⭐ Spongiform encephalopathy (vacuolation) is the characteristic CNS finding in Creutzfeldt-Jakob disease. Spongiform change in CJD

  • Frontotemporal Dementia (FTD) (Frontal Flare):
    • Pathology: Progressive frontotemporal lobar atrophy.
    • Key proteinopathies: Tau (e.g., Pick bodies) or TDP-43.
    • Clinical Variants:
      • Behavioral (bvFTD): Early personality/behavioral changes (disinhibition, apathy).
      • Primary Progressive Aphasia (PPA): Language deficits (semantic, nonfluent, logopenic).

High‑Yield Points - ⚡ Biggest Takeaways

  • Alzheimer's: Aβ plaques (extracellular), tau tangles (intraneuronal); ApoE4 major genetic risk.
  • Parkinson's: α-synuclein Lewy bodies in substantia nigra; marked dopamine loss.
  • Huntington's: Autosomal dominant CAG repeats (HTT gene); progressive caudate atrophy.
  • ALS: UMN & LMN degeneration; common proteinopathies include TDP-43 or SOD1.
  • Prion Diseases (CJD): PrPSc induces spongiform encephalopathy; rapidly fatal dementia.
  • FTD: Frontal/temporal lobar atrophy; characteristic tau (Pick bodies) or TDP-43 inclusions.

Practice Questions: Neurodegenerative Diseases

Test your understanding with these related questions

A 60-year old female presented with decreased movements for the last 2 years with rigidity and vertical large square wave jerks. The most likely diagnosis is?

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Flashcards: Neurodegenerative Diseases

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In chronic cases of Korsakoff's psychosis, there will be atrophy of the _____.

TAP TO REVEAL ANSWER

In chronic cases of Korsakoff's psychosis, there will be atrophy of the _____.

mamillary bodies

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