Specific Imaging Findings

The classic imaging finding is symmetric high signal on DWI and FLAIR images in the corpora striata (caudate and putamen), in the cerebral cortex, and possibly in the thalami. Isolated involvement of the cortex alone or the deep gray matter alone is less common. In the early phase of disease, signal changes may only be detectable on DWI, which is the most sensitive test for diagnosing CJD. There is no contrast enhancement. Diffusion changes persist for weeks to months, and may disappear in the late stages of disease. A prominent symmetrical hyperintense T2 and DWI signal in the pulvinar thalami (the “pulvinar sign”) is characteristic of variant CJD (vCJD). Involvement of the medial thalamus is also common, and the combination of both findings has been referred to as the “hockey-stick” sign. Signal changes in the pulvinar with sporadic CJD (sCJD) are less pronounced than changes in the striata.

Pertinent Clinical Information

The most common form of CJD, accounting for 85-90% of cases of human prion disease, is the sCJD. It typically occurs in the seventh decade of life with rapidly progressive dementia, focal neurologic signs and visual disturbances. CSF analysis for the presence of 14-3-3 proteins is 95% sensitive for the diagnosis of sCJD, but has a low specificity. EEG will show periodic sharp and slow wave complexes (PSWCs) in about 60–70% of patients with sCJD. The mean duration of this uniformly fatal disease is 6 months. vCJD has been linked with bovine spongiform encephalopathy (BSE, “mad cow disease”). It predominantly affects young patients (<30 years), has a more prolonged clinical course (median disease duration 14 months), and psychiatric features predominate early in its course.