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Inhaling pure oxygen might be able to repair brain damage years after concussion.

Concussions are common in contact sports and among soldiers. Most people recover after a short period of unconsciousness or amnesia, but up to 5 per cent experience long-term symptoms like headaches, mood changes, sleep disturbances and cognitive problems – known as post-concussion syndrome.

Former NFL player Ryan Miller, for example, went public earlier this year with his battle with migraines, depression, memory loss and seizures that have continued two years after his retirement from the league.


These neurological symptoms arise because impact to the head damages tiny blood vessels in the brain. This makes it harder for oxygen to reach and nourish brain cells.

Shai Efrati at Tel-Aviv University in Israel and his colleagues have been investigating whether hyperbaric oxygen therapy can help. The treatment involves sitting in a pressurised chamber and breathing 100 per cent oxygen to increase the amount of oxygen dissolving in the blood and flowing into the brain.

In a study published in 2013, the researchers found that 40 hyperbaric oxygen sessions lasting 1 hour each significantly improved cognitive functioning and quality of life in 56 people with post-concussion syndrome following car accidents, falls, assaults or other non-military injuries that occurred up to 6 years earlier.

Now, the researchers have used MRI to examine how hyperbaric oxygen has this healing effect. In 15 patients who sustained head injuries 6 months to 27 years earlier, the treatment was found to stimulate regrowth of blood vessels and nerve fibres. “Once the extra oxygen diffuses into damaged areas, it supplies energy and the regenerative process can happen,” says Efrati.

But does it really work?

The use of hyperbaric oxygen to treat post-concussion syndrome is controversial, because a major military trial published in 2015 concluded that it had no effect.

The study, which was run by Lindell Weaver at the University of Utah and his colleagues, found that hyperbaric oxygen benefited 72 military personnel with post-concussion syndrome, but no more than a “sham” treatment.

The sham involved sitting in a chamber with no extra oxygen but increased pressure to make it seem like the real deal. The problem was that the higher pressure would still have increased the amount of oxygen entering the bloodstream and brain, says Efrati. “It was meant to be a sham treatment, but it was actually an active treatment,” he says.

Weaver agrees this may have been the case. “The military population is also more complicated because of the high levels of PTSD and medication use, plus their injuries are different,” he says.

Adding to the confusion is that Weaver has just completed another study in 71 military personnel that found that hyperbaric oxygen therapy did in fact work better than a sham treatment – the same kind used in his previous study. “I think the burden of evidence is starting to suggest there is a favourable effect, but there are still lots of unanswered questions,” he says. His team is now inviting civilians with post-concussion syndrome to join another trial of hyperbaric oxygen.

Efrati says there is desperate need for post-concussion treatments, especially for former soldiers and sportspeople. It is estimated that one-quarter of military personnel who served in Iraq and Afghanistan sustained a head injury, and 244 concussions were recorded in the 2016 NFL season alone.

At this stage, there is no FDA-approved treatment for post-concussion syndrome. Antidepressants and other medications can be used to relieve symptoms but they don’t address the underlying causes, says Efrati. “We believe hyperbaric oxygen works and we now have 20,000 people on our waiting list from all over the world,” he says. “That suggests other people are convinced too.”

Journal reference: Frontiers in Human Neuroscience, DOI: 10.3389/fnhum.2017.00508