Neurology · MU Sofia

50. Transmissive spongiform encephalopathies

Covers prion-caused transmissible spongiform encephalopathies, starting with the definition and the aetiology of abnormal prion protein, then the pathogenesis of neuronal loss and vacuolisation. It then sets out a classification into sporadic, genetic and acquired forms, followed by the clinical features and examination findings. Diagnosis (EEG, MRI, CSF markers), differential diagnosis, prognosis and treatment close the note. Three pictures are included.

Inside: 1 section · 3 labelled pictures · 16 flashcards · 2 min

Topic 50 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 1 section, about 244 words (2 min of reading), with 16 flashcards.

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  1. Transmissive spongiorm encephalopathies

Transmissive spongiorm encephalopathies

Definition: Transmissible spongiform encephalopathies (TSEs) are a group of rare, fatal neurodegenerative diseases caused by prions (abnormal infectious proteins) leading to spongiform (vacuum-like) degeneration of the brain.

Etiology

Causative agent: PRIONS

  • Abnormal form of normal prion protein (PrPᴿᶜ)
  • Normal form: PrPᶜ
  • No DNA/RNA (infectious protein only)

Pathogenesis

  • Misfolded prion proteins accumulate in CNS
  • Induce misfolding of normal prion proteins
  • Leads to: Neuronal loss. Vacuolization (“spongiform change”). Astrocytosis. No significant inflammation

Classification of TSEs

A. Sporadic (most common): Creutzfeldt–Jakob disease (sCJD)

B. Genetic (familial): Familial CJD. Gerstmann–Sträussler–Scheinker syndrome. Fatal familial insomnia

C. Acquired (infectious): Variant CJD (from BSE “mad cow disease”). Iatrogenic CJD (medical procedures)

Clinical Features

  • Core Triad: Rapidly progressive dementia. Myoclonus. Ataxia
  • Neurological features: Behavioral changes. Memory impairment. Visual disturbances
  • Extrapyramidal signs (rigidity): Cerebellar ataxia
  • Late stage: Mutism. Akinesia. Coma → death

Examination Findings: Severe cognitive decline. Myoclonic jerks (stimulus-sensitive). Cerebellar dysfunction (ataxia). Pyramidal signs (hyperreflexia, Babinski). No fever or infection signs

Diagnosis

  • EEG: Periodic sharp wave complexes (classic in CJD)
  • MRI: “Pulvinar sign” (variant CJD). Diffuse cortical ribboning. Basal ganglia hyperintensity
  • CSF: Normal routine CSF. Special markers:. 14-3-3 protein (supportive, not fully specific)

Differential Diagnosis

1. SSPE: History of measles. Younger patients. Slower progression

2. Alzheimer disease: Slower progression. No myoclonus early

3. Viral encephalitis: Fever present. CSF inflammation

4. Metabolic/toxic encephalopathy: Potential reversibility. No characteristic EEG pattern

Prognosis: Always fatal. Rapid progression (months in sporadic CJD). No effective cure

Treatment: No curative therapy. Supportive care only. Symptom control (antiepileptics for myoclonus)

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