"Crab sign" in an ataxia patient with central nervous system Erdheim Chester disease: a novel neuroimaging finding with review of literature. - Mustafa F; Rajanna C; Makharia A; Garg D; Agarwal A; Garg A; Kakkar A; Ojha S; Damle NA; Dharmashaktu Y; Radhakrishnan DM; Srivastava AK (Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology, 2025)