Nearly half of people who have suffered concussion still show symptoms of brain injury six months later, a new study suggests.

With data compiled from across Europe, research from the University of Cambridge has found that for 45 percent of those who have had a blow to the head causing concussion, there are changes in how areas of the brain communicate.

And this can lead to long-term symptoms like cognitive impairment and tiredness.

"Mild traumatic brain injury – concussion – results from a blow or jolt to the head," stated the University of Cambridge website. "It can occur as a result of a fall, a sports injury or from a cycling accident or car crash, for example. 

"But despite being labelled 'mild,' it is commonly linked with persistent symptoms and incomplete recovery. Such symptoms include depression, cognitive impairment, headaches, and fatigue."

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While some recent studies have predicted that nine out of 10 people who have had concussion make a full recovery after six months, the research from the University of Cambridge suggests the real figure is fewer than half.

This in turn leads to the question of whether there is adequate care given to patients.

At present, patients with suspected concussion will typically receive a brain scan – either a CT scan or an MRI scan, both of which look for structural problems, such as inflammation or bruising – yet even if these scans show no obvious structural damage, a patient's symptoms may still persist.

"Worldwide, we're seeing an increase in the number of cases of mild traumatic brain injury, particularly from falls in our ageing population and rising numbers of road traffic collisions in low- and middle-income countries," said Emmanuel Stamatakis from the University of Cambridge's Department of Clinical Neurosciences and Division of Anaesthesia. 

"At present, we have no clear way of working out which of these patients will have a speedy recovery and which will take longer, and the combination of over-optimistic and imprecise prognoses means that some patients risk not receiving adequate care for their symptoms."

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In the study, functional MRI scans, which look at how different areas of the brain coordinate with each other, were looked at from 108 patients with concussion and the results were compared with scans from 76 healthy people.

The people involved in the study came from CENTER-TBI, a European research project which seeks to improve the care of patients with traumatic brain injury.

In results published in Brain, the team found that 45 percent were still showing symptoms resulting from their brain injury.

Abnormalities were found in the thalamus part of the brain which integrates sensory information and sends it around the brain.

Rebecca Woodrow, a PhD student in the department of clinical neuroscience at Hughes Hall, Cambridge, said: "Despite there being no obvious structural damage to the brain in routine scans, we saw clear evidence that the thalamus – the brain's relay system – was hyperconnected.

"We might interpret this as the thalamus trying to over-compensate for any anticipated damage, and this appears to be at the root of some of the long-lasting symptoms that patients experience."

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