Experimental Tx Restores Cognitive Function in Chronic TBI

An experimental therapy that uses deep brain stimulation (DBS) to deliver precise electrical pulses to an area deep inside the brain restored executive function in patients with moderate to severe traumatic brain injury (msTBI) and chronic sequelae.

Participants in this first-in-humans trial experienced brain injuries between 3-18 years before the study that left them with persistent neuropsychological impairment and a range of functional disabilities.

This is the first time a DBS device has been implanted in the central thalamus in humans, an area of the brain measuring only a few millimeters wide that helps regulate consciousness.

Placing the electrodes required a novel surgical technique developed by the investigators that included virtual models of each participant's brain, microelectrode recording, and neuroimaging to identify neuronal circuits affected by the TBI.

After 3 months of 12-hour daily DBS treatments, participants' performance on cognitive tests improved by an average of 32% from baseline. Participants were able to read books, watch TV shows, play video games, complete schoolwork, and felt significantly less fatigued during the day.

Although the small trial only included five patients, the work is already being hailed by other experts as a significant advance for patients with chronic msTBI, a condition for which there are no effective treatments.

Dr Nicholas Schiff

"We were looking for partial restoration of executive attention and expected [the treatment] would have an effect, but I wouldn't have anticipated the effect size we saw," co-lead investigator Nicholas Schiff, MD, professor of neuroscience at Weill Cornell Medical College, New York City, told Medscape Medical News.

The findings were published online today in Nature Medicine.

"No Trivial Feat"

An estimated 5.3 million children and adults are living with a permanent TBI-related disability in the US today. There currently is no effective therapy for impaired attention, executive function, working memory or information-processing speed caused by the initial injury.

Previous research suggests that a loss of activity in key brain circuits in the thalamus may be associated with a loss of cognitive function.

The investigators recruited six adults (four men and two women) between the ages of 22 and 60 years with a history of msTBI and chronic neuropsychological impairment and functional disability. One participant was later withdrawn from the trial for protocol noncompliance.

Participants completed a range of questionnaires and tests to establish baseline cognitive, psychological, and quality-of-life status.

To restore lost executive functioning in the brain, investigators had to target not only the central lateral nucleus, but also the neuronal network connected to the region that reaches other parts of the brain.

Dr Jaimie Henderson

"To do both of those things we had to develop a whole toolset in order to model both the target and trajectory, which had to be right to make it work properly," co-lead investigator Jaimie Henderson, MD, professor of neurosurgery at Stanford University College of Medicine, Stanford, California, told Medscape Medical News. "That gave us a pretty narrow window in which to work and getting an electrode accurately to this target is not a trivial feat."

"A Moving Target"

Each participant's brain physiology was slightly different, meaning the path that worked for one individual might not work for another. The surgery was further complicated by shifting in the brain that occurred as individual electrodes were placed.

"It was a literal moving target," Henderson said.

In the beginning, investigators used microelectrode recording to "listen" to individual neurons to see which ones weren't firing correctly.

When that method failed to offer the precise information needed for electrode placement, the investigators switched to neuroimaging, which allowed them to complete the surgery more quickly and accurately.

Participants remained in the hospital 1-2 days after surgery. They returned for postoperative imaging 30 days after surgery and were randomly assigned to different schedules for a 14-day titration period to optimize DBS stimulation.

The primary outcome was a 10% improvement on part B of the trail-making test, a neuropsychological test that measures executive functioning.

After 90 days of 12-hour daily DBS treatments, participants' scores increased 15%–52% (average 32%) from baseline. Participants also reported an average of 33% decline in fatigue, one of the most common side effects of msTBI, and an average 80% improvement in attention.

The main safety risk during the 3- to-4-hour procedure is bleeding, which didn't affect any of the participants in this study. One participant developed a surgical site infection, but all other side effects were mild.

After the 90-day treatment period, the study plan called for patients to be randomly assigned to a blinded withdrawal of treatment, with the DBS turned off for 21 days. Two of the patients declined to be randomized. DBS was turned off in one participant while the other two continued as normal.

After 3 weeks, the patient whose DBS was turned off showed a 34% decline on cognitive tests. The device was reactivated after the study and that participant has since reported improvements.

The DBS devices continue to function in all participants. Although their performance is not being measured as part of the study, anecdotal reports indicate sustained improvement in executive functioning.

"The brain injury causes this global down-regulation of brain function and what we think that this is doing is turning that back up again," Henderson said. "At a very simplistic level, what we're trying to do is turn the lights back up after the dimmer switch is switched down from the injury."

New Hope

TBI patients are usually treated aggressively during the first year, when significant improvements are most likely, but there are few therapeutic options beyond that time, said neurologist Javier Cardenas, MD, who commented on the findings for Medscape Medical News.

"Many providers throw their hands up after a year in terms of intervention and then we're always looking at potential declines over time," said Cardenas, director of the Concussion and Brain Injury Center at the Rockefeller Neuroscience Institution, West Virginia University, Morgantown. "Most people plateau and don't decline but we're always worried about a secondary decline in traumatic brain injury."

Surgery is usually only employed immediately following the brain injury. The notion of surgery as a therapeutic option years after the initial assault on the brain is novel, said Jimmy Yang, MD, assistant professor of neurologic surgery at Ohio State University College of Medicine, Columbus, who commented on the findings for Medscape Medical News.

"While deep brain stimulation surgery in clinical practice is specifically tailored to each patient we treat, this study goes a step further by integrating research tools that have not yet made it to the clinical realm," Yang said. "As a result, while these methods are not commonly used in clinical care, the overall strategy highlights how research advances are linked to clinical advances."

Investigators are working to secure funding for a larger phase 2 trial.

"With millions of people affected by traumatic brain injury but without effective therapies, this study brings hope that options are on the horizon to help these patients," Yang, MD, said.

The study was supported by funding from the National Institute of Health BRAIN Initiative and a grant from the Translational Science Center at Weill Cornell Medical College. Surgical implants were provided by Medtronic. Henderson and Schiff are listed as inventors on several patent applications for the experimental DBS therapy described in the study. Cardenas and Yang report no relevant financial relationships.

Kelli Whitlock Burton is a reporter for Medscape Medical News covering neurology and psychiatry.

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