Gadolinium is a rare earth metal that is used as a contrast agent in some MRI scans. When injected into the body, gadolinium enhances and brightens the images produced by the MRI scanner. This allows radiologists to better see abnormalities and disease processes. However, there have been concerns in recent years about gadolinium depositing in the brain and other body tissues.
How does gadolinium get into the brain?
Normally, gadolinium is quickly flushed out of the body through the kidneys. However, studies have shown that small amounts can remain in the brain and other organs for months or years after an MRI with a gadolinium-based contrast agent.
It is thought that gadolinium deposits form in the brain when the metal ion dissociates from its chelating agent. Contrast agents used for MRIs link gadolinium to a chelating molecule which renders the metal inert. But in some cases, the bond between gadolinium and chelator is not as strong as it should be. This allows free gadolinium to be released in the body.
Free gadolinium can interact with tissues and cross the blood-brain barrier. Over time, deposits accumulate in the brain, particularly in the dentate nucleus which is involved in learning and memory. Autopsy studies have detected gadolinium in neural tissue even in patients with normal kidney function.
Is gadolinium toxic to neurons?
The toxicity of gadolinium deposits in the brain is unclear. So far, there is no definitive evidence that gadolinium deposits alone cause neurological symptoms or brain damage.
However, studies in animal models have shown harmful effects including neuronal cell death and changes in neurotransmitters when gadolinium was administered at high doses. And patients with impaired kidney function who undergo multiple MRIs with gadolinium-based contrast agents have demonstrated neurological symptoms that could potentially be related to gadolinium toxicity.
More research is needed, but experts agree it is prudent to use gadolinium contrast only when necessary and limit repeated use in any individual patient.
What are the symptoms of gadolinium toxicity?
To date, no symptoms have been directly attributable to gadolinium deposition in the brain. As mentioned above, patients with kidney disease who underwent many MRI scans with gadolinium have developed debilitating and progressive symptoms including:
- Cognitive dysfunction
- Headache and bone pain
- Muscle spasms
- Dermatologic changes
However, these patients also had underlying conditions and comorbidities that likely contributed to their clinical presentation. Experts emphasize that more research is needed to clarify if gadolinium toxicity can cause neurological symptoms.
Does gadolinium cause cognitive problems?
There is no clear evidence that gadolinium deposits in the brain affect cognitive function or cause cognitive decline. Autopsy studies have detected gadolinium in the dentate nucleus which plays a role in learning, memory and attention. And animal studies have demonstrated cognitive effects of toxic gadolinium levels. However, the clinical significance of gadolinium retention in humans is still under investigation.
A few small studies have associated repeat gadolinium MRIs with poorer scores on tests of visual memory, abstract reasoning and executive function. But larger controlled studies are needed to determine if cognitive effects are directly attributable to gadolinium. At this point, no cognitive or behavioral symptoms have been definitively linked to gadolinium contrast.
Should I be concerned about gadolinium MRIs?
If you are undergoing an MRI with gadolinium contrast, there is likely no reason to be alarmed. The benefits of an enhanced scan for detecting medical conditions generally outweigh the potential and uncertain risks.
However, it is reasonable to avoid unnecessary gadolinium-enhanced MRIs when possible. Children, pregnant women and patients who require many repeat scans may want to be particularly cautious. Discuss any concerns with your doctor.
To minimize potential risks, the following precautions are recommended:
- Avoid repeat MRIs unless absolutely necessary
- Allow time between enhanced scans when possible
- Use lowest effective dose of gadolinium contrast
- Use more stable macrocylic gadolinium contrast agents
Patients with impaired kidney function are at increased risk for gadolinium retention and should discuss options with their doctor. Overall, experts agree more research is needed to better understand gadolinium deposition in the brain and its clinical significance.
Conclusion
Gadolinium contrast agents can allow MRI scans to detect abnormalities and diseases. But small amounts of gadolinium may remain in the brain for months or years after the scan. The clinical effects of gadolinium deposits are unclear but may potentially impact cognitive function. While larger studies are still needed, experts advise limiting gadolinium MRI use to necessary scans and minimizing repeat exposure, especially in vulnerable populations. Discuss any concerns with your health provider.