Between 100,000 and 300,000 Americans live in a kind of mental limbo. Due to major brain trauma, their minds are in a minimally conscious state, retaining a largely intact brain but showing little sign of consciousness and low levels of responsiveness. They may nod or shake their heads, but their communication is inconsistent and future unpromising; most will live permanently in a chronic-care center or nursing home. The mother of one such patient recalls, "It was hard for me to deal with seeing my son in bed, laying there, not being able to eat, not being able to show any signs of trying to communicate, and to know that my son would never speak again was very hard for me." (This mother wished to keep her family's identity private.)
Her 38-year-old son suffered severe brain injuries after being attacked and robbed in 1999. He spent six years in a minimally conscious state that doctors initially said he would never leave. But an experimental treatment for minimally conscious patients has changed that. The procedure, called Deep Brain Stimulation (DBS), involves surgically inserting a pacemakerlike device that regulates brain activity into the patient. While DBS has been used to treat movement diseases like Parkinson's for a decade, this was the first instance where it was applied to a minimally conscious patient.
The results of the treatment, published in the journal Nature this week, are extremely encouraging. One day after doctors at an East Coast rehabilitation center began using the device, this patient's eyes began to visually track others in the room. Then, he began speaking, typically in short, one- to three-word phrases. In the two years since the surgery, he has regained the ability to drink from a cup and to eat by mouth and his most recent accomplishment is reciting the first 16 words of the Pledge of Allegiance.
"These are large changes and for all of us they are important because they came six-plus years following a very severe injury to the brain and in an individual who was, at the time, in a minimally conscious state," says Joseph Giacino, a neuropsychologist at the JFK Johnson Rehabilitation Institute in Edison, N.J., and a coauthor of the study. "These are not the kind of changes one would expect to see spontaneously as a result of recovery from brain injury."
The patient is the first in a 12-patient study to investigate the effect of DBS on those in the minimally conscious state. The study authors are hoping to bring a new treatment to a population that typically has few options. They describe the minimally conscious as a consistently marginalized group, rarely examined and even more rarely cured. "These groups of patients are often young people with a severe disability and for the most part are forgotten about except by their families and immediate caregivers," says Ali Rezai, the neurosurgeon at the Cleveland Clinic who performed the DBS surgery. "They're often living in nursing homes or chronic care facilities with little hope."
The surgery involves implanting millimeter-wide electrodes into a deep brain structure at a particular location that has been targeted through brain mapping and imaging. The electrodes are attached to wires leading to batteries implanted in the chest. Rezai explains that it's quite similar to a heart pacemaker but "instead of the wire going to the heart, the wire goes to the brain." Once the device is inserted, doctors can remotely adjust the level and timing of the stimulation sent from the batteries to the electrodes in order to ensure the best dosage.
Researchers do not completely understand the exact mechanisms that make DBS treatment successful. They do know that it has something to do with changing the patterns of activity in the brain. "Most likely, we're activating areas of the brain that have a reduced activity and are essentially depressed in activity as a result of this severe trauma," says Rezai. The success of DBS in treating Parkinson's is likely due to the blockage of disruptive brain activity. Clinical trials are currently underway investigating its role as a possible treatment for obsessive-compulsive disorder, Tourette's and depression.
For minimally conscious patients, the success of the procedure depends on the patient's brain still being largely intact. This makes it an unlikely treatment for those in a permanent vegetative state (PVS) who exhibit no signs of consciousness. "The biological model for permanent vegetative state essentially would exclude the likelihood that this would work," says Nicholas Schiff, the study's lead author and neurologist at Weill Cornell Medical College in New York City. (Incidentally, one of the most well-known PVS-patients, Terry Schiavo, received DBS treatment in an earlier trial study and, due to the extent of her brain damage, the procedure was unsuccessful.)
The minimally conscious patient who has had success with DBS treatment is still far from a complete recovery. While he has made significant strides, the contraction of his muscles during the six years he spent immobile makes movement difficult. Doctors still do not know whether he will regain the ability to walk or even the motor skills to brush his teeth. Essentially, his body still has to catch up with his brain. But the extent of his recovery thus far makes them hopeful for minimally conscious patient population and future treatment. And it makes this patient's mother overjoyed. "I still cry every time I see my son," she says. "But it's tears of joy."