Dementias. Alzheimers disease
Definition
Dementia is a chronic progressive syndrome characterized by:
- Decline in memory
- Impairment of thinking, behavior, and daily functioning
- Without clouding of consciousness in early stages
The most common cause is Alzheimer Disease.
Classification of Dementias
A. Degenerative Dementias: Alzheimer disease (most common). Lewy body dementia. Frontotemporal dementia. Parkinson disease dementia
B. Vascular Dementia: Multi-infarct dementia. Small vessel disease
C. Secondary Dementias: Alcohol-related (Korsakoff syndrome). CNS infections (HIV, neurosyphilis). Tumors. Metabolic disorders (B12 deficiency, hypothyroidism)
Alzheimer Disease – Etiology & Risk Factors
- Risk Factors: Age (most important). Genetic predisposition (APOE-ε4). Family history. Female sex. Down syndrome. Cardiovascular risk factors
Pathogenesis
Key Mechanisms
- Accumulation of β-amyloid plaques
- Neurofibrillary tangles (tau protein)
- Neuronal loss → cortical atrophy
- Reduced acetylcholine (cholinergic deficit)
Brain Areas Affected: Hippocampus (early memory loss). Temporal and parietal cortex. Global cortical atrophy (late)
Clinical Features
Early Stage: Memory impairment (short-term memory first). Difficulty learning new information. Disorientation in time
Middle Stage: Language problems (aphasia). Apraxia (difficulty performing tasks). Agnosia (recognition impairment). Personality changes. Wandering behavior
Late Stage: Severe cognitive decline. Loss of speech. Inability to perform basic activities. Incontinence. Bedridden state
Cognitive Deficits (Key Triad): Memory impairment. Aphasia.Apraxia
Examination
Mental Status Examination: Mini-Mental State Examination (MMSE) ↓. Disorientation. Poor recall
Neurological Examination: Usually normal early
- Later: primitive reflexes, rigidity
Diagnosis
- Clinical Diagnosis: Progressive cognitive decline. Functional impairment
- Neuroimaging
- CT/MRI: Cortical atrophy (especially hippocampus). Enlarged ventricles
- Additional Tests
- Exclude reversible causes: B12 deficiency. Thyroid dysfunction. Infection (HIV, syphilis)
Differential Diagnosis
1. Vascular Dementia: Stepwise deterioration. Focal neurological signs
2. Lewy Body Dementia: Visual hallucinations. Parkinsonism
3. Frontotemporal Dementia: Early personality changes. Disinhibition
4. Depression (“Pseudodementia”): Reversible cognitive impairment
Treatment
Symptomatic Treatment
- Cholinesterase inhibitors: Donepezil. Rivastigmine
- NMDA receptor antagonist: Memantine.
Supportive Care: Cognitive stimulation. Caregiver support. Safety measures
Prognosis: Progressive and irreversible. Gradual loss of independence
- Average duration: 8–10 years