Prion diseases

Prion diseases, also known as transmissible spongiform encephalopathies, are caused by the accumulation of dysmorphic proteins named prions, and are characterised by progressive neurological decline and eventual death. In humans, these diseases include:

• Creutzfeldt-Jakob disease (sporadic, variant, familial and iatrogenic)
• fatal familial insomnia
• Gerstmann-Straussler-Scheinker disease
• kuru
• variably protease-sensitive prionopathy

Pathology

They are all mediated by prions: abnormally folded self-catalysing endogenous proteins which accumulate within the nervous system. Diagnosis has been problematic as imaging findings are variable and CSF protein analysis (14-3-3 protein) insensitive.

Brain biopsy is accurate but is fraught with difficulties as equipment needs to be discarded (prions have been found to survive standard autoclaving procedures) and staff precautions are difficult to implement.

Radiographic features

MRI

DWI changes are the earliest imaging manifestation prior to FLAIR and cerebral volume changes. Typically, cortical, cortical and deep grey matter (caudate, thalamus and putamen) demonstrates increased signal, not confined to vascular territories.

Treatment and prognosis

There is no curative treatment available for any prion disease.

History and etymology

The term spongiform is derived from the histological appearance of cerebral tissue characterised by neuronal degeneration with peculiar vacuolation reminiscent of a sponge. 

Although Creutzfeldt-Jakob disease had been clinically described in 1921, it wasn'twas not until 1959 when a similarity between kuru (only described in 1957) and scrapies (a similar disease affecting sheep) was recognised by W. J. Hadlow (a veterinary pathologist) that W J Hadlow, that prion disease was recognised as a group of related pathologies ².