Thursday, August 02, 2007

Jump-Starting the Damaged Brain

Electrical stimulation restores brain function in a minimally conscious patient.

By Emily Singer

Zapping the brain: Surgically implanted electrodes in the brain of a man with severe head injuries are connected to a pair of surgically implanted pacemakers. An illustration of the device is shown above. The programmable pacemakers deliver electricity to the brain via the electrodes, sparking activity in the brain. Researchers say that boosting activity in the thalamus, shown in close-up in the bottom image, improved both motor and cognitive function in this patient. Credit: Cleveland Clinic

Multimedia •  Watch an animation of electrodes and pacemakers delivering electric current.

Scientists have shown that electrically stimulating part of the brain can improve both mental and physical function in a patient with severe brain injury. The findings are a major step forward for the largely neglected group of patients who suffer serious impairments in consciousness that persist long after their initial injuries.

"He can eat, speak, watch a movie, and drink from a cup," said the patient's mother, who chose to remain anonymous, at a press conference on Wednesday held by the journal Nature, which published the study. Before her son, 38, participated in the study, she said that he had spent five years in a nursing home, where he was unable to eat and appeared largely unaware of his surroundings. "Now he can cry and he can laugh," she said. "He can say 'Mommy' and 'Pop.'"

In 1999, the woman's son suffered serious brain injuries after being robbed and beaten, his skull crushed. Following life-saving surgery, he remained in what neurologists call a minimally conscious state--a clinical category somewhere in the gray area between coma and consciousness. Unlike vegetative patients, who are defined as those totally unaware of their environment, patients in a minimally conscious state may occasionally and unreliably laugh or cry, reach for objects, or even respond to simple questions. Few reliable estimates exist on the number of people with this condition, but some researchers predict that there are as many as 280,000 minimally conscious patients in the United States.

Previous research on these patients suggests that some have a surprising level of brain activity. (See "Raising Consciousness.") Scientists theorize that some of the patients' neural circuits are left intact, occasionally becoming active or coordinated enough to allow the patients to respond to their environment. "We thought patients in this state might benefit [from stimulation] because they have the elements of language capability," said Nicholas Schiff, a neurologist and researcher at Weill Cornell Medical College, in New York, and one of the lead scientists on the study, at the press conference. "That shows that the intrinsic brain systems may be there and could potentially be restored."

Schiff and his colleagues employed a procedure called deep brain stimulation, which has been successfully used to treat thousands of people with Parkinson's disease and is currently in clinical trials for the treatment of depression, epilepsy, and chronic pain. Electrodes are surgically implanted into a specific part of the brain--the exact location depends on the condition--and connected via wires to a programmable pacemaker implanted in the chest. Doctors can then turn the device on and off, sending precise amounts of electrical current into the brain.

In the case of the minimally conscious patient, doctors targeted part of the thalamus, a structure that sits deep in the brain atop the brain stem. The thalamus transmits sensory information to other parts of the brain and plays a key role in regulating arousal. "These cells have wide projections to the cerebral cortex and basal ganglia, and have the capacity to increase brain activation globally," said Schiff. This part of the brain has also been shown to play a key role in disorders of consciousness. Scientists theorize that the targeted electrical current stimulates the resident cells and potentially the circuits to which they are connected.