Pou Hong Justin Chia, a graduate student at the Centre for Addiction and Mental Health in Toronto, has helped unlock a hidden dimension of multiple sclerosis—one that traditional imaging has never captured before. Using a specialized brain-scanning technique called SV2A PET, his team has revealed that MS patients lose not just the protective coating around their nerves, but something equally vital: the synapses themselves, those microscopic bridges where brain cells talk to one another.
Multiple sclerosis affects millions of people worldwide, bringing physical disability, fatigue, and cognitive fog that doctors have struggled to fully explain and measure. While neurologists have long known the disease damages myelin, the insulating layer around nerve fibers, they've largely overlooked a subtler form of damage unfolding silently in the brain. Synaptic loss—the dying away of connection points between neurons—happens in MS, yet until now, there was no way to see it in living patients. This gap in understanding has left clinicians unable to track a crucial marker of disease progression or to know whether new treatments are actually protecting these critical connections.
To bridge this gap, Chia and his colleagues at the University of Toronto, working with collaborators at Yale University, designed a dual-pronged study. First, they used an imaging tracer called 18F-SynVesT-1 to scan the spinal cords of mice with experimental autoimmune encephalomyelitis, a standard MS model. The results were striking: the technique successfully detected significant reductions in synaptic density within specific spinal cord regions, findings confirmed by follow-up binding studies.
Then came the translational leap. The team performed 11C-UCB-J PET imaging on six MS patients and six healthy controls, mapping synaptic density across the living brain. The comparison was sobering: MS patients showed a 16.4% reduction in synaptic binding across the brain compared to healthy controls. Widespread reductions appeared in subcortical regions and the spinal cord, echoing the synaptic damage the mouse studies had revealed. For the first time, researchers had confirmed in humans what they'd suspected: synaptic loss is not a rare feature of MS, but a widespread one.
Dr. Chao Zheng, the study's senior author, frames the significance plainly: this work establishes SV2A PET as a quantitative tool for monitoring synaptic pathology and evaluating future therapeutic strategies. It represents a new lens through which to view MS—not as a disease of insulation alone, but as one that erodes the very wiring of thought and movement at the cellular level.
For patients, the implications are profound. Understanding where and how synapses are lost can finally explain symptoms that current diagnostics miss: the cognitive fog, the fatigue, the subtle neurological shifts that don't show up on conventional MRI. For researchers, it opens a new window into how MS progresses. As Chia notes, this gives doctors and scientists "a more sensitive way to detect disease-related changes, monitor progression over time, and better understand how multiple sclerosis affects the brain and spinal cord." In a disease where early intervention matters, the ability to track synaptic health offers hope for catching damage before it accumulates into irreversible disability.