Doctors have woken a coma patient for the first time ever by jump-starting his brain using a pioneering ultrasound technique.

A saucer-sized device was put against the side of the 25-year-old patient's head over a 10 minute period.

Each of the 10 half-minute, low-intensity pulses created acoustic energy to stimulate brain tissue.

The patient's responses improved measurably within 24 hours. In three days he was fully conscious and had complete language comprehension.

He could nod his head "yes" or shake his head "no." He even made a fist-bump gesture to say goodbye to one of his doctors.

The unnamed man, who had shown only minimal signs of being conscious before the treatment at University of California, Los Angeles, has made "remarkable" progress since.

The ultrasound wakes brain nerve cells in the thalamus, which controls movement and consciousness.

The breakthrough, reported in medical journal Brain Stimulation, may lead to the development of a low-cost, helmet-like, ­portable device to wake patients.

Experts believe even those in a vegetative or minimally conscious state could benefit.