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 then relays messages deep into the brain.
About half of the 30 depressed 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
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 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 to see if they get the same effect. _ Help stroke or head-injury victims' memory recover.
In a study last year, epilepsy patients scored 36 percent 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.
These potential treatments require much more research to determine how to best stimulate the vagus nerve, said George. His depressed shipbuilder, for instance, was initially overstimulated into a hyper state associated with manic-depression. Later patients were better controlled.
But because the implant is so unique _ and can immediately be switched off if someone suffers a side effect _ scientists are encouraged.