‘Brain Pacemaker’ Studied as Depression Treatment
The former shipbuilder had severe depression unrelieved by any of today’s therapies, so sick he had trouble even leaving his house. Then doctors implanted a pacemaker-like device to stimulate a part of his brain thought important for mood--and that very day the man laughed.
“It was remarkable,” recalled Dr. Mark George of the Medical University of South Carolina, who performed the experimental implant. “I said, ‘Are you being forced to laugh or do you feel good inside?’ He said both.”
Stimulating a nerve that runs from the neck into one of the brain’s most mysterious regions appears promising enough at relieving once-untreatable depression that the government just granted permission for a study at 15 hospitals around the country.
The treatment, called vagus nerve stimulation, involves sending tiny electric shocks into the vagus nerve in the neck, where it relays messages deep into the brain.
About half of the 30 patients treated in a pilot study--people who had failed every other treatment--”got a very good response,” George said in an interview.
The results are not definitive, he cautioned. But he added, “Stimulating there really is a wonderful portal into the base of the brain.”
Indeed, scientists think stimulating this nerve could have even more far-reaching effects, such as enhancing memory or treating obesity by curbing appetite.
That’s because the vagus nerve is what Dr. Mitchell Roslin of Brooklyn’s Maimonedes Medical Center calls “one of the information superhighways” between the brain and other organs. It relays messages, such as signals to regulate heartbeat, and sends messages back to the brain, such as when the stomach is full.
The nerve also reaches deep into brain regions thought to regulate mood and emotion, said Dr. John Rush of the University of Texas Southwestern Medical Center, who heads the pilot depression study.
If the implant truly signals the depressed brain circuits to act more normally, it could prove important for some of the estimated 1 million Americans with depression uneased by conventional therapy.
The stimulator is essentially a brain pacemaker. A generator the size of a pocket watch is implanted into the chest. Wires snake up the neck to zap the nerve every few minutes. Two years ago, the Food and Drug Administration approved the implant to treat severe epilepsy, a way to signal the brain to reduce seizures.
Depression often accompanies epilepsy. Soon after the implants began selling, doctors began reporting epilepsy patients who felt happier even if the implant failed to reduce their seizures.
“There’s certainly an overlap between emotions and the site where people have intractable seizures,” said Dr. Cynthia Harden of Cornell University, author of one of those early studies.
So manufacturer Cyberonics Inc. funded a pilot study of patients with untreatable depression not complicated by epilepsy. Full results won’t be unveiled until December, but George said about half the patients responded well--prompting the FDA last week to approve a new study, beginning early next year at 15 hospitals, to prove the effect.
The vagus nerve might also:
* Fight obesity.
Because the nerve signals the brain when someone’s stomach is full, Roslin implanted Cyberonics stimulators in dogs to see whether they suppressed appetite. For a week, the dogs continued to gulp whatever food was in sight. But gradually their appetite dropped, until eventually they left half their food uneaten each day and lost one-third of their weight. Then Roslin switched off the stimulators, and within five days the dogs’ appetite and weight rebounded.
Roslin hopes to begin an implant study in obese New Yorkers early next year. .
* Help stroke or head-injury victims’ memory recover.
In a study last year, epilepsy patients scored 36% better at recalling words read just before their vagus nerve was stimulated. The theory: Emotional hormones seem to stimulate the vagus nerve to store memories, so maybe the implant could mimic that effect in injured patients.
