[A young patient with ischemic stroke due to carotid artery dissection in whom number of microembolic signals was followed-up].

A 23-year-old Japanese man with rheumatoid arthritis experienced attacks of the right hand weakness during the latest month. Megaloblastic anemia was diagnosed and he was admitted in the department of hematology. Seven days after admission, he developed mild consciousness disturbance and hemiparesis on the right side. Brain MRI revealed the cortical watershed infarction in the left cerebral hemisphere. The cause of the infarction was diagnosed spontaneous dissection of the left internal carotid artery. We detected 11 microembolic signals (MES) during 30 minutes' monitoring in the left middle cerebral artery using transcranial Doppler. MES decreased gradually with anticoagulant therapy. However, surgical therapy was performed to prevent progression of dissection or arterial rupture. MES detected on transcranial Doppler would be important to assess the risk of embolism and to discuss therapeutic strategy.