• Posted December 4, 2023

Head Injury Left Her Memory-Impaired. A New Brain Implant Has Brought Memory Back

Gina Arata had a bright future, wrapping up college and preparing for law school, when a 2001 car wreck left her with lasting brain damage.

After her recovery, Arata wound up taking a job sorting mail, but struggled even in that.

"I couldn't remember anything,"said Arata, who lives in Modesto with her parents. "My left foot dropped, so I'd trip over things all the time. I was always in car accidents. And I had no filter -- I'd get pissed off really easily."

But Arata is doing much better now, thanks to a device that doctors surgically implanted deep inside her brain in 2018. The experimental deep-brain stimulator is carefully calibrated to feed electrical activity to neural networks damaged by Arata's brain injury.

Now, a new study from Stanford researchers details how such implants help patients with brain injuries recover some of their thinking skills.

For Arata, the difference was immediate.

For example, the device allowed her to rattle off a list of fruits and vegetables when asked to name items found in the produce aisle of a grocery store. But when a researcher turned the device off, she couldn't name a single one.

"Since the implant, I haven't had any speeding tickets,"Arata added. "I don't trip anymore. I can remember how much money is in my bank account. I wasn't able to read, but after the implant I bought a book, 'Where the Crawdads Sing,' and loved it and remembered it. And I don't have that quick temper."

The device has restored, to different degrees, thinking abilities that Arata and four other patients lost to brain injuries years before, researchers report.

This new technique is the first to show promise in righting long-lasting impairments caused by traumatic brain injuries, the investigators noted. The findings were published Dec. 4 in the journal Nature Medicine.

New hope for treatment

More than 5 million Americans live with lasting effects from traumatic brain injuries, researchers said in background notes. These include difficulty focusing, memory problems and impaired decision-making ability.

Many recover enough to live independently, but their impairments keep them from returning to the life they had prior to their injury.

"In general, there's very little in the way of treatment for these patients,"co-senior researcher said Dr. Jaimie Henderson, a professor of neurosurgery at Stanford Medicine.

The five patients in the new study all had emerged from comas and had since recovered a fair amount of their cognitive function. That suggested to Henderson and colleagues that the brain systems that support the ability to stay awake, pay attention and focus on a task had been all relatively preserved, despite brain injury.

Those systems all connect the thalamus -- which serves as a relay station deep inside the brain -- to different points across the cortex, which is the brain's outer layer and the place where higher thinking functions are located.

"In these patients, those pathways are largely intact, but everything has been down-regulated,"Henderson explained in a Stanford news release. "It's as if the lights had been dimmed and there just wasn't enough electricity to turn them back up."

Researchers focused in particular on an area of the thalamus called the central lateral nucleus, which acts as a hub that regulates many aspects of human consciousness.

"The central lateral nucleus is optimized to drive things broadly, but its vulnerability is that if you have a multifocal injury, it tends to take a greater hit because a hit can come from almost anywhere in the brain,"explained co-researcher Dr. Nicholas Schiff, a professor of neurology at Weill Cornell Medicine in New York City.

The research team postulated that precise electrical stimulation of the central lateral nucleus and its connections could reactivate these pathways, essentially turning the lights back up for people struggling with the aftermath of brain injury.

Precise targeting

The researchers recruited Arata and four other people still suffering thinking problems more than two years after a traumatic brain injury. The patients ranged in age from 22 to 60, and had injuries they'd sustained three to 18 years earlier.

The first challenge was placing the stimulation device in the exact right place. Each person's brain is shaped differently, so the location varies from patient to patient.

Researchers created a virtual model of each person's brain that would allow them to pinpoint the exact location for the implant, as well as the level of electrical stimulation needed to activate the central lateral nucleus.

"It's important to target the area precisely,"he noted. "If you're even a few millimeters off target, you're outside the effective zone."

Following the implant surgery, the participants spent 90 days with the device turned on for 12 hours a day.

Researchers tracked their progress using a standard test of mental processing speed called the trail-making test. The test involves drawing lines that connect a jumble of letters and numbers.

"It's a very sensitive test of exactly the things that we're looking at: the ability to focus, concentrate and plan, and to do this in a way that is sensitive to time,"Henderson said.

Researchers had hoped that participants would improve their score on the test by at least 10% during the trial.

Astonishingly, participants instead improved their speeds on the test by an average of 32%, researchers report.

'A pioneering moment'

The benefits of the device also quickly became apparent in the daily lives of the patients.

They resumed normal activities that had once seemed impossible, like reading books, watching TV shows, playing video games or finishing a homework assignment. They felt less fatigued and could get through the day without napping, researchers said.

The device was so effective that researchers had trouble completing the final phase of the clinical trial.

They'd planned to randomly select half the patients and turn off their devices, then compare their brain performance to that of those with devices still active.

But two of the patients declined, unwilling to take the chance that they'd lose the progress they had made over the 90-day trial period.

Of the three who agreed to participate in this final phase, one was chosen randomly to have the device turned off. After three weeks without stimulation, that person performed 34% slower on the trail-making test.

This trial was the first attempt to target this region of the brain in hopes of treating traumatic brain injury, researchers said. They say the results offer hope to people who are struggling to fully recover their thinking function.

"This is a pioneering moment,"Schiff said. "Our goal now is to try to take the systematic steps to make this a therapy. This is enough of a signal for us to make every effort."

More information

Johns Hopkins Medicine has more about deep brain stimulation.

SOURCE: Stanford Medicine, news release, Dec. 4, 2023