Diffusion-weighted MR Imaging of Early-Stage Creutzfeldt-Jakob Disease: Typical and Atypical Manifestations

Abstract

Creutzfeldt-Jakob disease causes progressive dementia and, eventually, death. The infectious agent is thought to be proteinaceous scrapie particles. Prompt diagnosis is essential to prevent human-to-human transmission. Progressive brain atrophy and areas of high signal intensity in the cerebral cortex and basal ganglia are well-known features of Creutzfeldt-Jakob disease depicted on T2-weighted magnetic resonance (MR) images. However, in the early stage of disease, the appearance of the brain on T2-weighted MR images often is normal, and it may be impossible on that basis to reach a diagnosis. Diffusion-weighted imaging therefore has gained attention as a useful modality for the early diagnosis of Creutzfeldt-Jakob disease. Even before the appearance of the characteristic periodic synchronous discharges on the electroencephalogram, diffusion-weighted images in most cases of Creutzfeldt-Jakob disease depict areas of abnormal signal hyperintensity in the cortex and in the basal ganglia or thalamus. These imaging abnormalities are accompanied by decreased apparent diffusion coefficient values suggestive of restricted diffusion within the tissue. However, if diffusion-weighted imaging findings of abnormal high signal intensity are restricted to the cerebral cortex, it may be necessary to differentiate between Creutzfeldt-Jakob disease and other conditions that may produce progressive dementia (eg, venous hypertensive en-cephalopathy; chronic herpes encephalitis; and the syndrome of mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes).

Enhanced Detection of Diffusion Reductions in Creutzfeldt-Jakob Disease at a Higher B Factor

“…Case reports have previously described unilateral signal-intensity abnormalities in MR imaging of patients with CJD, but studies with larger samples consistently showed bilateral involvement. [24][25][26][27][28][29][30][31] In the current study, we have confirmed bilaterally reduced ADC in the putamen at b ϭ 1000 s/mm 2 with a more liberal statistical significance level (P Ͻ .005). We believe the absence of bilateral findings in the putamen at b ϭ 1000 s/mm 2 merely reflects its lower statistical power.…”

Imaging of prion diseases

“…Gadolinium administration may be a helpful adjunct in this circumstance because enhancement is reported in Wernicke's encephalopathy whereas it is not a feature of CJD. Finally, an underrecognized cause of rapidly progressive but potentially reversible dementia is venous congestive encephalopathy secondary to dural arteriovenous malformation (16,97). In our experience, restricted diffusion is uncommonly seen, but venous hypertension may result in different pattern of parenchymal edema.…”

“…However, these reports have the potential of being flawed by the time delay between the imaging and autopsy, especially given the fact that the histological changes are known to evolve spatially over time. Indeed, DWI findings may become less conspicuous in the terminal stage of the disease and may even normalize (8,(16)(17)(18). This evolution may be related to increased gliosis, producing increased water diffusivity, thus balancing the restricted diffusion seen earlier in the disease (11,19).…”

“…As an adjunct to conventional imaging findings, MR spectroscopy can demonstrate nonspecific decrease in NAA (and various NAA ratios), likely secondary to neuronal loss or dysfunction as well as increased myoinositol (and corresponding ratios), correlating with gliosis (11,16,54). MRS changes also appear to be topographically associated with areas involved on pathological examination and may be seen in areas otherwise normal on other sequences (11).…”

Neuroimaging of Rapidly Progressive Dementias, Part 2: Prion, Inflammatory, Neoplastic, and Other Etiologies

“…12,13 In the much less common Japanese encephalitis, these abnormalities tend to be seen in subcortical gray matter regions. 13 Patchy enhancement with gadolinium administration indicates nonspecific inflammatory changes generally seen in encephalitis.…”