Diffusion- and perfusion-weighted brain magnetic resonance imaging in patients with neurologic complications after cardiac surgery

Background: Neurologic complications after cardiac surgery include stroke, encephalopathy, and persistent cognitive impairments. More precise neuroima ging of patients with these complications may lead to a better understandin g of the etiology and treatment of these disorders. Objective: To study the pattern of ischemic changes on diffusion- and perfu sion-weighted magnetic resonance imaging (DWI, and MRPI, respectively) in p atients with neurologic complications after cardiac surgery. Methods: All records were reviewed of our patients undergoing cardiac surge ry in the previous year who also underwent postoperative DWI or MRPI. Neuro logic symptoms, vascular studies, and the pattern of ischemic changes were recorded. Acute ischemic lesions were classified as having a territorial, w atershed, or lacunar pattern of infarction. Patients with multiple territor ial infarcts in differing vascular distributions that were not explained by occlusive vascular lesions were classified as having multiple emboli. Results: Fourteen patients underwent DWI and 4 underwent MRPI. Acute infarc ts were found in 10 of 14 patients by DWI as compared with 5 of 12 patients by computed tomography. Eight patients presented with encephalopathy (asso ciated with focal neurologic deficits in 4), 4 with focal deficits alone, a nd 2 with either fluctuating symptoms or transient ischemic attacks. Among patients with encephalopathy, 7 of 8 had patterns of infarction suggestive of multiple emboli, including 3 of 4 patients with no focal neurologic defi cits. Several patients had combined watershed and multiple embolic patterns of ischemia. Findings of MRPI studies were abnormal in 2 of 4 patients, sh owing diffusion-perfusion mismatch; both patients had either fluctuating de ficits or transient ischemic attacks, and their conditions improved with bl ood pressure manipulation. Conclusions: In patients with neurologic symptoms after cardiac surgery, DW I is more sensitive to ischemic change than computed tomographic scanning a nd can demonstrate patterns of infarction that may help us understand etiol ogy. The most common pattern was multiple embolic infarcts. Preliminary exp erience with MRPI suggests that some patients have persistent diffusion-per fusion mismatch after surgery and may benefit from therapeutic intervention .