A surgically implanted "pacemaker for the brain" significantly improves depression - and its benefits last for at least two years, according to the results of the first long-term follow-up study of the treatment. Vagus nerve stimulation (VNS) is conventionally used to treat severe cases of epilepsy. The VNS device consists of an electrode, which is wrapped around the vagus nerve in the neck, and a pulse generator. The pulse generator is inserted into an opening in the chest. It is programmed to stimulate the nerve in 30-second bursts, sending impulses into the limbic area of the brain - an area linked to mood. After patients using the device showed notable improvement in mood, the manufacturer, Cyberonics, commissioned a pilot study of its effectiveness in depression, which was completed in 1999. That study found that 60 people who had failed to improve after taking two or three existing anti-depression medications showed a 60 per cent improvement after surgery to implant a VNS device. However, the most treatment-resistant - those who failed on more than eight medications - did not respond to the surgery. Anthony Cleare, head of the department of neurobiology of mood disorders at the UK's Institute of Psychiatry says he is still uncertain over the role VNS has in treating depression. "I don't think it will be used widely, because it requires surgery and the device is there for life. Also it has side-effects. Every five minutes the box discharges for 30 seconds, which causes the patient's voice to become hoarse." Depression is estimated to affect up to 12 per cent of men and 25 per cent of women worldwide.
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