Prion Infections of the Brain

Prions are a rare cause of human disease but very important to recognize because of their potential for transmissibility and uniformly severe outcome. MR imaging plays an extremely important role in early diagnosis, especially with diffusion-weighted and fluid-attenuated inversion recovery images, which are the most sensitive for depicting prion-induced brain lesions. The lesions are characteristically shown as ribbons of cortical hyperintensity, or basal ganglia or thalamic hyperintensity. The cortical and deep lesions may appear alone or together, and although usually bilateral and symmetric, they may be asymmetric or purely unilateral. When these MRI findings are observed in an appropriate clinical context, the diagnosis of prion disease is very likely.