Three severely brain-injured people thought to be in an irreversible “vegetative” state showed signs of full consciousness when tested with a relatively inexpensive and commonly used method of measuring brain waves, doctors reported Wednesday. Experts said the findings, if replicated, would change standards in treating such patients.

Scientists have seen meaningful, responsive brain activity in such patients before, using a high-tech magnetic resonance imaging scanner, and in at least two cases, using an electroencephalogram machine, or EEG. But the new report, posted online Wednesday by the journal The Lancet, is the first to test this innovative EEG strategy in a larger group of patients. The EEG is a portable, widely available unit that picks up electrical brain activity through electrodes positioned on a person’s head. Clinics and homes treating people with severe brain injuries are far more likely to have access to an EEG than to an M.R.I. scanner.

An estimated 25,000 Americans with brain injuries are living in an unresponsive state diagnosed as vegetative, and friends and family members typically long for some way to reach through the empty mask — to see whether there is any life behind those familiar eyes. If the new approach holds up, an EEG could provide that, and perhaps even a way to communicate.

“My personal view is that you don’t introduce anything like this into routine clinical practice until” larger trials at multiple clinics confirm its value, said Joseph T. Giacino, the director of rehabilitation neuropsychology at Spaulding Rehabilitation Hospital, who was not involved in the research. “But it sure looks as if there’s not just a little bit of consciousness but a lot” in patients who had been deemed unresponsive.