ObjectiveTo investigate the MRI manifestations of internal carotid artery dissection (ICAD) before and after treatment. MethodsMRI materials of 20 patients with ICAD between November 2007 and February 2013 were collected for analysis. ResultsMRI manifestations of ICAD showed 17 cases of artery stenosis, 16 cases of mural hematoma or thrombus, 3 cases of aneurysmal dilatation, and 2 cases of lines of intimal flap. The treatment outcome MRI manifestations showed that 18 patients had effective response, including disappeared (n=9) and lessened (n=8) artery stenosis, disappeared (n=13) and diminished (n=3) hematoma and thrombus, and shrunken aneurysmal dilatation (n=1); and there were 2 cases of unchanged aneurysmal dilatation, and another 2 patients had aneurysmal dilatation while stenosis lessened. ConclusionMRI manifestations of internal carotid artery dissection mainly include stenosis, mural hematoma or thrombus, and aneurysmal dilatation. Stenosis, mural hematoma or thrombus usually disappear and lessen in the treatment, and all MRI findings may vary among each other.