Researchers in the US have pioneered the use of ultrasound to successfully 'restart' brain activity in a coma patient for the first time.
It's too early to say if the technique will be safe and effective every time, but it could give doctors a non-invasive option for treating those who would otherwise be stuck in a vegetative state.
The 25-year-old patient who was given the ultrasound boost was being treated by medical researchers from the University of California, Los Angeles (UCLA), and hospital staff say he's making "remarkable progress" after the procedure.
"It's almost as if we were jumpstarting the neurons back into function," says lead researcher Martin Monti.
Before now, a process known as deep brain stimulation could be used to achieve the same effects, in an attempt to 'wake up' coma patients. But that treatment is risky and invasive, with electrodes implanted directly into the brain's thalamus - a region that regulates alertness, and is central to the way the brain handles information flow.
Instead, ultrasound can be applied from outside the body while still targeting the thalamus directly, and this is the first time the technique has been used in the case of a serious brain injury.
But the researchers warn that it's still early days, and further study is required before this technique becomes common practice. "It is possible that we were just very lucky and happened to have stimulated the patient just as he was spontaneously recovering," explains Monti.
In the space of three days after treatment, the patient went from showing only minimal signs of alertness and understanding to a state of full consciousness. He could nod his head for yes, shake his head for no, and even fist-bumped one of the doctors.
If ultrasound does prove to be effective in getting a response from coma patients who are only minimally conscious, it's possible a treatment like this could even be applied one day using a portable device, without any need for a hospital trip or surgery.
The specific technique is known as low-intensity focused ultrasound pulsation, and the benefits it offers are being very precise in both the area it targets and the modulations it produces. It's previously been applied to reduce seizures in epilepsy patients.
Also central to the new procedure is a saucer-shaped device that creates a blast of sonic energy targeted to the brain. In this treatment, it was activated 10 times for 30 seconds each over the course of 30 minutes, but it only produces a small amount of energy compared with a regular Doppler ultrasound (used to look at foetuses in the womb).
Eventually, the device could be adapted into a low-cost helmet, Monti says, which could give new hopes of recovery for those trapped in the depths of a coma.
The findings have been published in Brain Stimulation.