Imaging Spectrum of Brain Microhemorrhages on SWI

Microhemorrhages in cerebral and cerebellar parenchyma are due to various underlying causes. Conventional MR imaging sequences and CT are often not sufficient for their detection and determination of their distribution. SWI is a relatively new full-velocity‐compensated high-resolution 3-dimensional gradient echo sequence that accurately detects small hemorrhage (microhemorrhage) and calcification by exaggerating susceptibility signal intensity, which is more sensitive than T2 gradient echo. Increased availability of SWI has identified its utility in a wide range of other brain abnormalities. Here we presented and discussed various pathologies with brain microhemorrhages on SWI. We retrospectively reviewed cases with SWI. When available, we also compared the SWI with other MR imaging sequences and/or CT. SWI was particularly helpful for the detection and determination of distribution of microhemorrhages, which were more conspicuous than on CT or conventional MR imaging sequences. Some diseases had distinctive patterns of microhemorrhages as follows: in the deep subcortical white matter, posterior corpus callosum, and midbrain location for diffuse axonal injuries; cortical for amyloid angiopathy; peripheral in sickle cell disease; basal ganglia and cerebellar for hypertensive microhemorrhages; perivascular for invasive mucormycosis; and diffuse involvement in fat emboli. However, in some entities, the distribution of microhemorrhages was nonspecific, and, in these patients, clinical information and history were helpful in reaching a correct diagnosis.

Learning Objective: To identify the distinctive imaging features on SWI of various pathologies, which may help in generating a differential diagnosis and in achieving a definite diagnosis.