Diagnostic accuracy of diffusion-weighted imaging in variant Creutzfeldt–Jakob disease

PURPOSE: This study sought to investigate the diagnostic sensitivity of diffusion-weighted imaging (DWI) in variant Creutzfeldt-Jakob disease (vCJD), a prion disease with significant public health implications on account of its transmissibility. The importance of this research stemmed from the first neuropathologically confirmed vCJD case in a PRNP heterozygous individual in 2016, which displayed DWI features typical of sporadic CJD (sCJD). The case was classified as ‘probable’ sCJD in life, predominantly based on these imaging findings. While DWI has proven valuable in diagnosing sCJD, its utility in vCJD diagnosis remains unclear. METHODS: DWI and Fluid-attenuated inversion recovery (FLAIR) images from probable and definite vCJD cases referred to the National CJD Research and Surveillance Unit (NCJDRSU) were independently analysed by an expert neuroradiologist. Scans were reviewed within a mixed cohort of CJD cases including definite sCJD and non-CJD controls. RESULTS: FLAIR sequences demonstrated greater sensitivity in identifying the pulvinar sign in vCJD compared to DWI (73% vs 41%, p-value <0.001). Basal ganglia hyperintensities were more prevalent in DWI (84%) than FLAIR (64%), and cortical hyperintensities were exclusive to DWI (24%). The pulvinar sign showed a specificity of 98% for vCJD and was rare in sCJD. CONCLUSION: DWI showed reduced sensitivity compared to FLAIR imaging in detecting the pulvinar sign in vCJD. Conversely, DWI can more distinctively identify basal ganglia and cortical hyperintensities, thus leading to imaging patterns more characteristic of sCJD. Therefore, DWI should be cautiously interpreted in vCJD diagnosis, with axial FLAIR potentially providing a more precise evaluation of the pulvinar sign.