Gadolinium from imaging contrast agents sticks to neural tissues even in patients who don’t have intracranial abnormalities, according to a small, single-center, retrospective study.

In a postmortem study comparing tissues from the brains of five patients who had several magnetic resonance imaging (MRI) scans using gadolinium with 10 patients who had MRIs without contrast, elemental gadolinium was detected in four neuroanatomic regions of all five patients, with concentrations ranging from 0.1 to 19.4 mcg per gram of tissue, Robert McDonald, MD, PhD, of the Mayo Clinic in Rochester, Minn., and colleagues reported online in Radiology. No gadolinium was detected in the brains of controls.

“Our results suggest that current thinking with regard to the permeability of the blood brain barrier is greatly oversimplified, as gadolinium appears to accumulate even among patients with normal brain tissue and no history of intracranial pathology,” McDonald said in a statement. “It will take additional research to understand how and why this deposition is occurring.”

The authors were quick to note, however, that they did not find any histologic changes that suggested toxicity. However, further investigation is needed, they said, “in light of the cytotoxic and genotoxic potential of free lanthanide rare earth metals.”

Just last month, the FDA similarly concluded that there are no adverse health effects from gadolinium retained in the brain after contrast MRI, so restricting use of the agent is not warranted. But the agency said it would have a public meeting on the issue in the future.

McDonald and colleagues said their study bolsters previous research in patients who have intracranial abnormalities — underlying brain pathology such as a tumor or infection that was thought to be the culprit behind gadolinium buildup.