[Clinical significance of cerebral microbleed and its diagnostic criteria]

Cerebral microbleed (CMB) on gradient-echo T2*-weighted MR imaging (T2*-w MR imaging) is associated with microangiopathy. Number of CMBs and new appeared CMBs are markers for stroke recurrence and the performance state. After CMB was reviewed in this manuscript, criterion for CMB is proposed as below. (1) Only microbleed associated with microangiopathies related to primary intracerebral hemorrhage or lacunar infarction is diagnosed as CMB. (2) A low intensity (round or oval shape, <7 mm in diameter) on T2*-w MR imaging defined as a CMB. Exception: (A) Micro-bleedings associated with trauma (cerebral concussion), brain tumor, cavernous angioma, or moyamoya disease are excluded. (B) Calcifications or vascular flow voids were excluded by CT or other MR imagings. Reference: (C) CMB is rarely correlated to a focal neurological sign. (D) CMB is associated with risk factors including hypertension, diabetes mellitus, or high age. CMB is very rare in patients less than 40 years old.