Gadolinium Builds Even in Normal Brains | Medpage Today – by Kristina Fiore Kristina Fiore, Deputy Managing Editor, MedPage Today June 29, 2017
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,”
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.”
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.
But in the McDonald et al study, the researchers assessed patients who had contrast MRI mainly for gut imaging, to test the hypothesis that gadolinium accumulation would occur in those with normal brains, too, as some recent evidence has suggested.
Overall, McDonald and colleagues found dose-dependent gadolinium deposits in four neuroanatomical brain regions in those who had contrast MRI, with concentrations ranging from 0.1 to 19.4 mcg of gadolinium per gram of tissue.
These were highest in the globus pallidus and in the dentate nucleus.
Both the globus pallidus and the dentate nucleus are prone to mineralization and hemorrhage, which “may suggest that parts of the brain may have a less robust barrier and may be more susceptible to this deposition,” McDonald explained. In addition, gadolinium is similar to calcium in size and charge, so the body may mistake it for the endogenous metal, which is often taken up in areas of brain as patients age.
Patients with multiple sclerosis (MS) have long been raising questions about frequent contrast-enhancing brain scans, but MS experts contacted by MedPage Today said the new results don’t have any impact on current practice — notably because the data are from people without underlying brain pathology.
“In a stable [MS] patient, it does not add that much info, especially in older stable patients,” Corboy said of gadolinium-enhancing scans. “So, we use them for diagnosis, for clinical changes, and to rule out other pathology as needed — for example, a brain tumor.
Otherwise, we try to avoid it.
We can also use different dyes that have lesser risks of being taken up in brain or other tissues.”
If they can use different dyes with lesser risks, why aren’t they?
“While there is currently no evidence of any harmful effects of retained gadolinium, since this issue has arisen, we now determine on each ordered scan whether gadolinium is needed,” he said.