A novel PET radiotracer can help identify changes in the brain’s grey matter that may be indicative of progressive multiple sclerosis (MS), according to a pilot study published in the July issue of Neurology: Neuroimmunology & Neuroinflammation.
The tracer—[F-18]PBR06—can detect abnormal activation in the brain’s microglia—an area influential in emotion, memory and cognition, reported corresponding author Tarun Singhal, MD, a neurologist at the Ann Romney Center for Neurologic Diseases at Brigham and Women’s Hospital in Boston. The radiotracer also revealed a link to brain atrophy, physical disability and progressive MS.
"Unless we can measure the progress of a disease accurately, our ability to treat that disease remains limited," Singhal said in a prepared statement. "When a patient tells us that their symptoms are worsening, we want to have a technology that can reflect that, or better yet, predict the progression before it is clinically obvious. This technique may have the potential to do that and give us critical insights into neurodegeneration and its relationship with neuroinflammation."
MS patients experience worsening physical, mental and mood-related symptoms over time, but the brain white matter lesions identified on MRI scans often remain the same. This led Singhal and colleagues to believe there might be other areas of the brain at fault.
"There's more to multiple sclerosis than white matter lesions," Singhal added. "There's evidence of inflammation in the brain's grey matter, not just the white matter.”
The researchers evaluated the standardized uptake values (SUVs) of [F-18]PBR06 in 12 patients with MS—seven with relapsing remitting MS and five with secondary progressive MS—comparing their results to five healthy participants.
Grey matter microglial activation was greater in MS patients compared to the controls. This was particularly true in the hippocampus, parahippocampus, cingulate gyrus and amygdala. In secondary progressive MS patients, microglial activation was higher in the thalamus compared to the other cohorts. This, Singhal et al. noted, correlated greatly with physical disability and brain atrophy.
While the patient population is this study was small, the authors acknowledged, the F-18 tracer’s significantly longer half-life—compared to other isotopes such as C-11—has great potential for furthering their research.
“This is the first study of [F-18]PBR06 PET, assessing gray matter changes in MS, demonstrating potential value of this technique,” the researchers wrote. “The practical advantages of this longer half-life tracer have implications for its potential clinical use in the long term, and hence, larger studies with longitudinal design are needed to confirm and extend the findings of our pilot study.”