- Alzheimer Disease
- Proteins: Extracellular Amyloid-β plaques & Intracellular hyperphosphorylated Tau tangles.
- Key Feature: Progressive memory loss.
- Genetics: ApoE4 (risk), APP, Presenilin-1/2 (familial).
- Path: Atrophy of the hippocampus.
- Parkinson Disease / Lewy Body Dementia
- Protein: α-synuclein.
- Pathology: Forms intracellular Lewy bodies.
- Parkinson’s: Motor sx (tremor, rigidity, bradykinesia). Loss of neurons in substantia nigra.
- LBD: Parkinsonism + visual hallucinations + fluctuating cognition.
- Huntington Disease
- Protein: Mutated Huntingtin.
- Genetics: Autosomal dominant CAG trinucleotide repeat expansion.
- Key Feature: Chorea, dementia, psychiatric sx.
- Path: Atrophy of caudate and putamen.
- Frontotemporal Dementia (FTD) / ALS
- Protein: TDP-43.
- FTD: Early personality/behavioral changes or aphasia.
- ALS: Combined UMN and LMN signs (spasticity + fasciculations/atrophy).
- Prion Disease (Creutzfeldt-Jakob)
- Protein: Misfolded Prion Protein (PrPsc).
- Pathology: Spongiform encephalopathy.
- Key Feature: Rapidly progressive dementia + myoclonus.