With 56 million people worldwide suffering from concussion each year, the short-term symptoms such as a headache, nausea, sensitivity to light and problems concentrating are common. However, long-term symptoms are also prevalent and include fatigue, trouble sleeping and concentrating, and emotional distress. A recent study published in Brain found that almost half of people who suffer a concussion do not fully recover six months after their injury. The study analyzed brain scans from over 100 patients who had recently experienced concussion from all across Europe, using a technique called resting-state functional MRI which measures brain activity when a person is at rest. Unlike CT scans or MRI which only look for structural changes in the brain such as inflammation or bruising, a resting-state fMRI can identify more subtle changes in brain function, which could help to predict who is more likely to develop long-term symptoms. The study found that an increased functional connectivity between the thalamus and the rest of the brain very shortly after injury was associated with post-concussive symptoms. It shows that even a single brain injury can have clear consequences, which may not show up in routine scans, suggesting it may be time to expand the types of imaging used.