A.5 Neuropathology of eight cases of the New Brunswick cluster of Neurological Syndrome of Unknown Cause (NSUC)

Background: In March 2021, at a press conference, the presence of a cluster of patients, claimed to have a novel neurological syndrome, was announced in New Brunswick. These patients were suggested to have symptoms reminiscent of CJD. The onset of disease was between 2015 and 2021. The size of this cluster has been reported as approximately 50 cases. Further news publications have suggested that various environmental factors were causing this disease. Methods: Between 2019 and 2021 eight patients have died in this cluster. Their neuropathological findings are reported here. Results: There was one case of metastatic carcinoma, one case of FTLD-TDP43, one case of neocortical Lewy body pathology, one case of neocortical Lewy body pathology and AD, 2 cases of AD with vascular pathology, one case of mainly vascular pathology, and one case without significant pathology (consistent with patient’s history). In all these patients no evidence for a prion disease was found, nor novel pathology. Conclusions: We suggest that these 8 patients represent a group of misclassified clinical diagnoses. Classical probability theorem based statistical evaluation shows that this group of deceased patients is representative for the entire cluster at a p=0.0001 level, which would suggest that the entire cluster is based on misdiagnoses.