Toward an early clinical diagnosis of MM2‐type sporadic Creutzfeldt–Jakob disease

OBJECTIVE: To assess the proportion of clinically diagnosed MM2‐type sporadic Creutzfeldt–Jakob disease (sCJD) in a Chinese cohort, describe the clinical features of MM2‐cortical (MM2C) and MM2‐thalamic (MM2T) type sCJD to improve the early detection of MM2‐type sCJD. METHODS: A total of 209 patients with sCJD admitted to the Xuanwu Hospital between February 2012 and August 2022 were reviewed. The patients were classified into probable MM2C, MM2T‐type sCJD, and other types of sCJD according to current clinical diagnostic criteria. Clinical and ancillary data were compared between the groups. RESULTS: Fifty‐one (24.4%) patients were clinically diagnosed with MM2‐type sCJD, of which 44 were diagnosed with MM2C‐type sCJD and 7 with MM2T‐type sCJD. In the absence of RT‐QuIC, 27 (61.3%) patients of MM2C‐type sCJD did not meet the US CDC sCJD criteria for possible sCJD on admission, even though the mean period from onset to admission was 6.0 months. However, all of these patients had cortical hyperintensity on DWI. Compared to the other types of sCJD, MM2C‐type sCJD was associated with slower disease progression and the absence of the typical clinical features of sCJD; the MM2T‐type sCJD group had a higher proportion of males, earlier age of onset, longer duration of disease, and a higher incidence of bilateral thalamic hypometabolism/hypoperfusion. INTERPRETATION: In the absence of multiple typical sCJD symptoms within 6 months, the presence of cortical hyperintensity on DWI should raise concerns for MM2C‐type sCJD after excluding other etiologies. Bilateral thalamic hypometabolism/hypoperfusion may be more helpful in the clinical diagnosis of MM2T‐type sCJD.