Prion diseases

1. Big picture

Prion diseases are rare, fatal, transmissible neurodegenerative diseases caused by abnormal misfolded prion protein. They are important in the neurology exam because they cause rapidly progressive dementia, usually with myoclonus, ataxia, extrapyramidal/pyramidal signs, and characteristic supportive findings on MRI, CSF, and EEG.

The key exam sentence:

Think of prion disease when a patient develops rapidly progressive dementia over weeks to months, especially with myoclonus, ataxia, pyramidal or extrapyramidal signs, and typical MRI/EEG/CSF findings.

The most important exam trap:

Prions are “protein-only” infectious agents without nu