WEDNESDAY, April 26, 2023 (HealthDay News) -- A significant number of patients take far longer to recover from a concussion than expected, and they may not be getting the care they need, according to a new study.

Researchers from the United Kingdom who studied concussion patients found that almost half had changes in how regions of the brain communicate with each other. This may cause long-term symptoms, including fatigue, and impaired thinking and memory.

Mild traumatic brain injury can happen in a fall, a sports incident, or from a cycling accident or car crash.

Although called "mild," it is commonly linked with persistent symptoms including depression, cognitive impairment, headaches and fatigue, as well as incomplete recovery.

The researchers said only about half of people who suffer a concussion are fully recovered within six months, far less than the 90% some other recent studies have predicted.

A CT scan or an MRI scan looks for signs of structural damage, such as inflammation or bruising after a concussion.

In this study, researchers used an fMRI, or functional MRI, which looked at how different areas of the brain coordinate with each other.

“Worldwide, we’re seeing an increase in the number of cases of mild traumatic brain injury, particularly from falls in our aging population and rising numbers of road traffic collisions in low- and middle-income countries,” said study co-author Emmanuel Stamatakis, leader of the Cognition and Consciousness Imaging Group at the University of Cambridge.

“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,” he explained in a university news release.

For the study, Stamatakis and his team compared fMRI scans from 108 patients with mild traumatic brain injury with those from 76 healthy volunteers. They also assessed patients for ongoing symptoms.

About 45% were still having symptoms after their brain injury, including fatigue, poor concentration and headaches.

These patients had abnormalities in the brain area called the thalamus. This region integrates all sensory information and relays this information around the brain.

Somehow, concussion was associated with increased connectivity between the thalamus and the rest of the brain. With this increased connectivity, as the thalamus was trying to communicate more, a patient's prognosis was poorer.

“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,” said Rebecca Woodrow, a doctoral student. "We might interpret this as the thalamus trying to overcompensate for any anticipated damage, and this appears to be at the root of some of the long-lasting symptoms that patients experience."

The researchers also studied additional data from PET (positron emission tomography) scans. These can measure regional chemical composition of body tissues.

The team was able to make associations with key neurotransmitters depending on which long-term symptoms a patient displayed.

In patients who were having cognitive problems, such as memory difficulties, the team saw increased connectivity between the thalamus and brain areas that have a lot of the neurotransmitter noradrenaline.

In those with depression or irritability, the researchers saw greater connectivity with areas of the brain rich in serotonin.

“We know that there are already drugs that target these brain chemicals so our findings offer hope that in future, not only might we be able to predict a patient’s prognosis, but we may also be able to offer a treatment targeting their particular symptoms,” Stamatakis said.

The study findings were published April 26 in the journal Brain.

More information

The U.S. Centers for Disease Control and Prevention has more on concussion.

SOURCE: University of Cambridge, news release, April 25, 2023