Investigators from Brigham and Women's Hospital suspected that changes in the grey matter regions of the brain may be playing a critical role in multiple sclerosis disease progression. The researchers conducted an initial study assessing the differences in the activity of microglial cells in the grey matter regions of healthy volunteers versus those with MS. The team used a novel tracer molecule known as [F-18]PBR06 and positron emission tomography imaging and detected widespread and abnormal activation of microglia in MS patients and a link to brain atrophy, physical disability, and progressive MS. 

The new study uses the novel radioisotope, [F-18]PBR06, a tracer that targets a specific protein found in activated microglia, key immune cells found in the brain. Many other research projects use C-11, an isotope with a much shorter half-life. But, unlike C-11, the F-18 tracer has a significantly longer half-life and a higher potential to be used in the clinic.

For the pilot study, investigators evaluated results for 12 patients with MS –  seven with relapsing remitting MS and five with secondary progressive MS – and compared it with healthy controls using the F-18 tracer. They found more grey matter microglial activation in the MS patients as compared to healthy controls, particularly in hippocampus, parahippocampus, cingulate gyrus and amygdala regions of the brain. These regions of the brain are known to influence critical processes, including emotion, memory and cognition, all of which may be affected in MS patients. Brain structures in the deep grey matter, particularly the thalamus, showed higher microglial activation in secondary progressive MS than in the relapsing remitting MS patients and healthy controls. This correlated significantly with physical disability and brain atrophy.

The authors note that the pilot study is small and its findings will require additional confirmation in larger studies with a longitudinal design, but it offers the first assessment of [F-18]PBR06 PET for grey matter changes in MS, demonstrating the potential value of this technique.

The findings were published in Neurology: Neuroimmunology & Neuroinflammation.