An unexpected finding involving gadolinium-based contrast agents and stroke patients has prompted researchers from the U.S. National Institutes of Health (NIH) to further explore the ocular effects of MRI exams in stroke patients.

The research, published online Feb. 7 in Neurology, found that gadolinium leakage into eyes of acute stroke patients is common for those receiving MRI scans. The study did not reveal what caused the leakage, though clinical consequences exist because of it. 

"We found gadolinium leakage into ocular structures (GLOS) to be common in patients with acute stroke; delayed GLOS was a marker for chronic vascular disease," wrote lead author Emi Hitomi, a post baccalaureate intramural research training award fellow at the NIH, and colleagues. "The mechanism for acute GLOS remains uncertain but may be a remote effect of acute cerebral injury on the blood–ocular barrier." 

The NIH researchers selected 167 study participants who underwent an MRI examination when admitted to the hospital. For research purposes, all participants underwent an initial MRI scan as a baseline and then a fluid-attenuated inversion recovery (FLAIR) imaging exam two hours and 24 hours later, according to study methods. 

Gadolinium leakage was found in 76 percent of participants, according to the study. After the two-hour follow-up examination, leakage was found in 67 percent of participants in the aqueous chambers of the eye, compared to 6 percent of participants who showed evidence of leakage in the vitreous chambers. 

Additionally, 27 percent of participants had leakage in both chambers and consequently had larger infarcts and "a higher degree of blood–brain barrier permeability," researchers concluded. 

After the 24-hour follow up exam, gadolinium leakage was present in 75 percent of participants in the vitreous chambers alone. Researchers concluded its association with increasing age and a higher burden of cerebral white matter hyperintensities.