Creutzfeldt-Jakob disease (CJD) is a rare cause of dementia with rapid and progressive course.
It has an incidence of approximately one case per million individuals each year. Most cases of CJD are sporadic but up to 10–15% are inherited and transmitted by autosomal dominant means.
CJD is one of several neurodegenerative diseases which are caused by a non-viral, 30- to 35-kDa proteinaceous particle called a prion. Pathologically, there is neuronal loss and astrocytosis with formation of intracytoplasmic vacuoles within the neurons and glia, which is responsible for the spongiform appearance on light microscopy.
The pathology in CJD involves the cerebral and cerebellar cortices and the basal ganglia. The patients often develop dementia rapidly and many develop myoclonus particularly late in the disease. The disease is uniformly fatal with survival of less than 1 year after the onset of symptoms.
The CT and MRI scans early on may be normal. Symmetrical increased T2 signal intensity of the basal ganglia may be the earliest changes and may occasionally appear before clinical signs (Barboriak et al. 1994; Di Rocco et al. 1993; Milton et al. 1991; Tartaro et al. 1993). Diffusionweighted imaging (DWI) is very sensitive in detecting early stages even prior to development of FLAIR signal abnormality. In fact, DWI is more sensitive in identifying the abnormalities of the gray matter than routine MRI sequences (Parazzini et al. 2003). On DWI symmetrical decreased diffusion in the basal ganglia is characteristic of CJD. Decrease in diffusion may also be detected in the thalami and cerebral cortex, but the abnormality in these regions tends to be less symmetrical. Analyzing ADC measurements may increase sensitivity for detection of gray matter abnormality in patients with CJD (Henriette et al. 2003). Reduction in movement of water in the intracytoplasmic vacuoles of spongiform encephalitis is thought to be the cause of Brownian motion derangements that are detected on DWI (Bahn and Parchi 1999; Demaerel et al. 1997). Decrease in N-acetyl-aspartate and other metabolites in late CJD have been shown on MR spectroscopy (Graham et al. 1993).
In late stages, the patients develop marked atrophy, and serial MRI scans reveal rapidly progressive atrophy. It is important to keep in mind that a normal initial MRI does not rule out CJD.