Major and Mild Neurocognitive Disorders (NCDs)
*(DSM-5 Classification of Cognitive Impairment)*
Key Distinctions
| Feature | Mild NCD | Major NCD (Dementia) |
|---|---|---|
| Cognitive Decline | Modest, measurable impairment | Significant, interferes with independence |
| Daily Function | Preserved independence | Requires assistance |
| Progression | May stabilize or progress | Typically progressive |
| Diagnostic Certainty | 0.5-1 SD below norms | ≥2 SD below norms |
Etiological Subtypes
1. Alzheimer’s Disease
- Hallmarks: Amyloid plaques, neurofibrillary tangles
- Early Signs: Episodic memory loss → language/visuospatial deficits
2. Vascular NCD
- Hallmarks: Stepwise decline, focal neurological signs
- Risk Factors: Hypertension, stroke history
3. Lewy Body Disease
- Hallmarks: Fluctuating cognition, visual hallucinations, parkinsonism
4. Frontotemporal NCD
- Subtypes:
- Behavioral variant (personality changes)
- Primary progressive aphasia
5. Other Causes:
- TBI, HIV, Huntington’s, prion diseases, substance-induced
Diagnostic Workup
1. Clinical History
- Informant interviews (e.g., AD8 questionnaire)
- Timeline of symptom progression
2. Cognitive Testing
- Brief Screens: MoCA, MMSE (Mild NCD: MoCA 18-25/30; Major: <18)
- Detailed: Neuropsychological battery
3. Labs & Imaging
- Rule Out: B12 deficiency, hypothyroidism, neurosyphilis
- MRI/CT: Atrophy patterns (e.g., hippocampal in Alzheimer’s)
- Advanced: Amyloid PET, CSF biomarkers (e.g., tau/Aβ42)
Management Strategies
Pharmacologic:
- Alzheimer’s: AChE inhibitors (donepezil), memantine
- Parkinson’s/Lewy Body: Caution with antipsychotics (risk sensitivity)
Non-Pharmacologic:
- Cognitive rehabilitation
- Environmental modifications (safety proofing)
- Caregiver support (respite, training)
Prevention:
- Mediterranean diet
- Aerobic exercise
- Cognitive/social engagement
Prognosis
| Disorder | Typical Course |
|---|---|
| Alzheimer’s | 8-10 year progression |
| Vascular | Stepwise decline, plateaus |
| Lewy Body | Rapid progression (5-7 years) |
Clinical Pearls
- Mild NCD: 15% annual conversion to major NCD
- Reversible Mimics: Depression (“pseudodementia”), delirium
- Legal Implications: Early capacity assessments