[A case of ticlopidine-associated thrombotic thrombocytopenic purpura: special emphasis on diffusion weighted MRI]

A 69-year-old man of thrombotic thrombocytopenic purpura (TTP) associated with ticlopidine was reported. The patient initially complained of dysarthria and left hemiparesis one month after oral administration of ticlopidine. These motor symptoms were followed by gradual deline in level of consciousness. On admission, he was in apallic state with focal cerebral signs, accompanied by low-grade fever, and purpuric eruptions. Laboratory findings showed remarkable thrombocytopenia, hemolytic anemia, and renal dysfunction. The patient received diagnosis of TTP based on Moschcowitzs criteria. Prompt initiation of plasma exchange dramatically improved the patient's clinical symptoms. In this case, decreased activities of a disintegrin and metallo proteinase with thrombospondin type 1 motifs 13 (ADAMTS13) in plasma and anti-ADAMTS13 IgG antibodies were detected. Serial diffusion weighted MRI with six-day interval starting from the onset showed two interesting findings. First, appearance and disappearance of scattered high intensity areas were observed in the cerebellum, corpus callosum, cerebral white matter, and neocortex. Second, these lesions roughly corresponded to border-zone infarct in distribution. Cranial MRI findings of TTP in the literature could be classified into the following four groups: 1) multiple infarction caused by microthrombi; 2) infarction caused by occulusion of an intracranial main artery; 3) reversible edema involving the cerebral white matter; and 4) unremarkable finding without specific abnormality. This case could be classified into the group 1. Based on the diffusion weighted MRI findings of this case, a previous pathological report and recent elucidations of clinical conditions, it is hypothesized that TTP is a predisposition for resembling the border-zone infarction in group 1. The border-zone distribution of transient high intensity areas in diffusion weighted MRI in this case could be explained by either high resistant vascules zone or impaired clearance of emboli, taking an autopsy case report into consideration.