A new study from Lawson Health Research Institute and the Institute for Clinical Evaluative Sciences (ICES) has cast doubt on the clinical significance of brain deposits of gadolinium (a chemical contrast agent commonly used to enhance MRI imaging).
In 2015, the US Food and Drug Administration raised safety concerns over reports of retained gadolinium in the brain for patients undergoing four or more gadolinium-enhanced MRIs. The FDA launched an inquiry at the time, stating that "it is unknown whether these gadolinium deposits are harmful." Pending further investigation, the FDA suggested limiting the use of gadolinium-based contrast agents (GBCAs) to circumstances where contrast information is clinically necessary, and to evaluate the need for repetitive GBCA MRIs based on treatment protocols.
Studies since that time have shown deposits of gadolinium may be found long after they are administered. They tend to concentrate in the globus pallidi, a region of the brain that can cause parkinsonian symptoms if it is damaged. Parkinson's disease is an example of a specific brain disorder that is commonly associated with parkinsonian symptoms.
"Given the concern around possible neurotoxicity of gadolinium, and because these deposits were found in the globus pallidi region of the brain, we wanted to see if people exposed to gadolinium MRIs have higher rates of subsequent parkinsonism," says Dr. Blayne Welk, the lead author of the study who is an adjunct scientist with ICES Western and Lawson.
To test a possible link between GBCAs and parkinsonism, Welk and his team examined anonymized health care records for 246,557 patients in Ontario over the age of 66 who underwent an initial MRI in a 10-year period between 2003 and 2013. They excluded patients whose initial MRI was of the brain or spinal cord and those with prior parkinsonism or neurosurgery. Comparing patients who were exposed to gadolinium-enhanced MRIs with patients whose MRIs did not include gadolinium enhancement, they looked for differences in rates of future parkinsonism symptoms or treatment.
They found that the rates of parkinsonism for exposed vs non-exposed patients were virtually identical, at 1.2 per cent. These findings indicate that there is no increased risk for parkinsonism associated with the use of gadolinium in MRIs.
However, the researchers caution that this study does not clear up all the worries about gadolinium, since they investigated only its connection to parkinsonism.
"While these findings should be reassuring for patients and their care providers that gadolinium exposure does not appear to be associated with higher risk of developing parkinsonism symptoms, there have been other reports of nonspecific neurologic symptoms including pain and cognitive changes associated with prior gadolinium exposure which do require further study," comments Dr. Welk.
The researchers also note that gadolinium may have different effects in younger patients (who were not included in this study), or in those with neurologic diseases (who may have been excluded based on the types of MRIs included in this study).
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