Six years after being kicked in the head repeatedly during a mugging that left him unable to walk, talk, feed himself or respond to people, a 38-year-old man has improved with the help of electrodes implanted deep in his brain.
Thanks to a technique called deep brain stimulation, in which these electrodes receive pulses of electrical current from a pacemaker surgically placed under the skin of his chest, researchers report in the Aug. 2 issue of Nature that the man, whose identity has not been disclosed, is far more alert and aware.
Nicholas Schiff, assistant professor of neurology and neuroscience at the Weill Medical College of Cornell University in New York, and colleagues report that the man keeps his eyes open most of the time during the day and can follow people with his eyes as they move around the room. He communicates reliably with gestures as well as with audible phrases of up to six words. He still has a feeding tube, but now takes all of his meals by mouth.
“My son can now speak, watch a movie without falling asleep, drink from a cup, express pain, laugh, and say, ‘I love you, mommy,’ ” the man’s mother told a group of reporters during a conference call Aug. 1.
The electrodes in deep-brain stimulation transmit the current from the pacemaker to the thalamus, which rests on top of the brain stem. In this case, the implant is on for 12 hours at a time, then off for 12 hours.
The technique has been approved by the FDA for quelling the tremors of Parkinson’s disease. It also appears to elevate the mood of people with intractable depression, and is being tested for the treatment of Tourette syndrome, obsessive-compulsive disorder, phantom limb pain and even migraine headaches.
Although the mechanism that produces improvements in these conditions remains largely unknown, the electrical pulses delivered to the relevant brain areas apparently disrupt the activity that produces the symptoms. Schiff suspected that implanting electrodes into the thalamus, at the core of the brain, might rouse patients in a minimally conscious state to a higher level of interaction with their environment.
“Over the last 10 to 20 years, basic scientific research has identified that neurons in this area have wide projections to the cerebral cortex and basal ganglia and have the capacity to increase overall brain activation,” Schiff said during the call. “Most of the systems in the brain stem and the frontal cortex that control the level of brain activation project into the areas of the central thalamus we identified for stimulation. We were hoping we would be able to partially restore the normal function of the central thalamus just by increasing its output (through stimulation).”
The study lasted 480 days, ending in February 2006, and the man has continued to improve since then.
“One of the most compelling changes we observed was his ability to say the first 16 words of the Pledge of Allegiance without prompting when asked,” Joseph T. Giacino, associate director of neuropsychology at the JFK Johnson Rehabilitation Institute in Edison, N.J., said during the call. “He’s now a reliable communicator. You can believe him when he nods his head yes or no. He does it consistently and accurately.”
Because of his brain injury, the man’s ligaments have contracted, limiting his use of his hands, arms and legs.
“Whether he will have sufficient power to support himself in standing is uncertain,” Giacino said.
This is the first of 12 minimally conscious subjects who will have deep-brain stimulation of the thalamus, Schiff said. The results will shed light on the ability of brain-damaged patients to recover consciousness.
“This directs our attention particularly to the integration of the processes needed to establish the conscious state,” he said. “Consciousness as a brain function is about allowing us to be part of the human community, and part of what needs to happen is, parts of the brain need to talk to each other.”