254.2 📚 國考版

254.2.0.1 必背 — Prion Concept

• Proteinaceous infectious particle (PrPSc)
• PrPC (cellular) → PrPSc (pathologic) misfolding + propagation
• Resistant to standard sterilization (heat, formalin, UV)
• Transmissible Spongiform Encephalopathy (TSE)

254.2.0.2 必背 — CJD Forms

Form	Frequency	Features
Sporadic (sCJD)	85%	Age 60+; rapid progressive dementia + myoclonus + ataxia; median survival 4-6 mo
Familial (fCJD)	10-15%	PRNP mutations; earlier onset
Iatrogenic (iCJD)	< 5%	Medical procedures (historic)
Variant (vCJD)	< 1%	BSE-related (UK 1990s+); younger (28 yr); tonsil + appendix biopsy +

254.2.0.3 必背 — Sporadic CJD Clinical

• Rapidly progressive dementia + myoclonus + ataxia + visual disturbances + extrapyramidal
• Median survival 4-6 months from onset

254.2.0.4 必背 — vCJD

• BSE-contaminated beef (UK 1990s)
• Younger onset (median 28 yr)
• Psychiatric / sensory symptoms early
• Tonsil + appendix biopsy PrPSc +

254.2.0.5 必背 — Other Prion Diseases

• GSS: familial cerebellar ataxia + dementia; slow
• FFI: progressive insomnia + dysautonomia + dementia
• Kuru: cannibalism transmission (extinct PNG)

254.2.0.6 必背 — Animal Prion Diseases

• Scrapie (sheep)
• BSE (mad cow; UK 1980s+)
• CWD (deer + elk; N America expanding)
• Feline spongiform encephalopathy

254.2.0.7 必背 — Diagnosis

• MRI:
  • Cortical ribbon sign + basal ganglia hyperintensity
  • “Hockey stick sign” (medial thalamus + pulvinar) — vCJD
• EEG: periodic sharp wave complexes (PSWC) in sporadic CJD
• CSF:
  • 14-3-3 protein elevation (nonspecific)
  • Total tau elevation
  • RT-QuIC (most specific + sensitive 95%+)
• Tonsil + appendix biopsy: PrPSc + in vCJD
• Brain biopsy / autopsy: definitive

254.2.0.8 必背 — Treatment

• NO PROVEN TREATMENT
• Universally fatal
• Supportive care + hospice
• Anti-myoclonic (clonazepam)
• Symptom management

254.2.0.9 必背 — Prevention + Infection Control

• Special prion decontamination for surgical instruments (autoclave + chemical)
• Disposable instruments for high-risk CNS procedures
• Blood donor screening for BSE risk (UK residents 1980-1996)
• No general bioterror concern

254.2.0.10 必背 — Differential Rapidly Progressive Dementia

• CJD (prion)
• Autoimmune encephalitis (anti-NMDA, anti-LGI1, others — treatable!)
• Viral encephalitis (HSV)
• Vascular dementia (multiple infarcts)
• Heavy metal poisoning
• Hashimoto encephalopathy
• Frontotemporal dementia (slower)
• Limbic encephalitis (paraneoplastic)
• Wernicke encephalopathy
• Workup: rule out treatable causes critical

---