Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) is a spongiform encephalopathy that results in a rapidly progressive dementia and other non-specific neurological features. 

Epidemiology

Three types of Creutzfeldt-Jakob disease have been described ^2,6:

• sporadic (sCJD) : accounts for 85 - 90 % of cases
• variant (vCJD)
• familial (fCJD) : 10 % of cases : these individuals carry a PRPc mutation

Clinical presentation

Creutzfeldt-Jakob disease is characterized by rapidly progressive dementia, cerebral atrophy, myoclonus and death. Patients with vCJD present mostly with sensory and psychiatric symptoms; patients with sCJD usually present with progressive cognitive impairment and cerebellar symptoms.

Diagnostic markers

• characteristic results on electroencephalography (EEG)
• S100
• 14-3-3 protein : For patients with suspected CJD, CSF 14-3-3 assays should be performed. In diagnosing CJD ( the sensitivity is 92%, specificity  is 80% ).
  A negative 14-3-3 assay may be helpful in reducing the suspicion of sCJD, a positive CSF 14-3-3 assay may be found in a potentially treatable case of dementia. These findings need to be correlated with patients history as CSF 14-3-3 can be false positive in treatable dementing disorders.^7-8

A definitive diagnosis requires a brain biopsy, although in many institutions the difficulty involved in sterilising equipment renders a biopsy undesirable. 

Pathology

CJD is thought to be mediated via (infectious) prions,( a type of protein) which manifest in sheep as the disease scrapie, and in cows as bovine spongiform encephalopathy. Prions are considered infectious in sense that they can alter the structure of neighbouring proteins. 

CJD leads to spongiform degeneration of the brain, which is thought to be caused by the conversion of normal prion protein to proteinaceous infectious particles that accumulate in and around neurons and lead to cell death.

Radiographic features

MRI

MRI findings may be bilateral or unilateral and symmetric or asymmetric, and include:

• T2 hyperintensity
  • basal ganglia (putamen and caudate)
  • thalamus (see hockey stick sign and pulvinar sign)
  • cortex : most common early manifestation
  • white matter
• restricted diffusion on DWI (considered the most sensitive sign)
• hypo-metabolism on ¹⁸FDG-PET studies

Review of sequential studies also typically demonstrates rapidly progressive cerebral atrophy.

Treatment and prognosis

There is currently no curative treatment and the disease is invariably fatal with a mean survival of only 7 months for most cases.