Scientists Find Brain Scans Show Physical Damage Behind Long COVID Brain Fog

For years, the brain fog, fatigue, and loss of motivation reported by long COVID patients have been difficult to pin down with standard medical tests, leaving many patients feeling dismissed even as their symptoms persisted. A new brain imaging study out of Toronto offers what researchers describe as the first clear biological explanation.

Researchers at the Centre for Addiction and Mental Health and the University of Toronto, led by Jeffrey Meyer, used PET scans to measure a protein called VMAT2 that sits on the nerve terminals responsible for releasing dopamine in the brain. Comparing 24 long COVID patients with 24 healthy volunteers, the team found significantly lower levels of that protein across the striatum, a brain region central to motivation, movement, and memory.

A Consistent Pattern Tied to Specific Symptoms

The reductions were not uniform across the brain, and that variation lined up closely with the specific symptoms each patient reported. Lower levels in the ventral striatum correlated with a greater loss of motivation, reduced levels in the dorsal putamen were tied to slower movement, and lower levels in the caudate were linked to memory difficulties. Across the group, the average loss of dopamine releasing nerve terminals came out to roughly 18 percent, with the sharpest reductions reaching 20 percent in some regions.

Meyer and his colleagues describe the findings as the first measurable, consistent evidence connecting long COVID symptoms to a specific, physical form of brain injury, rather than a vaguer or purely psychological explanation that some patients have struggled against for years.

A Path Toward Treatment

The discovery points toward treatments already used for other conditions involving the dopamine system. Meyer has suggested that medications which support dopamine releasing neurons, including dopamine precursors and drugs that slow the breakdown of dopamine, could help long COVID patients. He has filed a pending patent application, submitted in January, covering a treatment approach that combines the drug rasagiline with a tyramine based dopamine precursor specifically aimed at long COVID.

The research also offers a note of encouragement for recovery. Meyer said some patients may see damaged nerve terminals regrow or form new connections over time, particularly when supported by exercise or other activities that actively engage the brain regions affected by the condition. While the findings will need to be confirmed in larger studies, they give doctors and patients a concrete biological target for a condition that has often lacked one.