NEW YORK - A technique called deep brain stimulation may relieve chronic cluster headaches that do not respond to standard medication, according to a study reported this month in the medical journal Cephalalgia.

Cluster headaches cause sudden, severe pain, often centered in one eye. Though the headaches tend to be short, they run in cycles, which may cause several headaches in one day or every few days. Most people with cluster headaches experience pain-free periods of several weeks or more between each headache cycle. About 10 percent of sufferers, however, experience chronic cycles, which can last a year or more.

In 4 of 6 chronic cluster headache patients, deep brain stimulation, which involves surgically implanting electrodes that deliver a small electric current into a targeted area of the brain, led to a profound decrease in attack frequency and pain intensity during the first 6 months, Dr. Thorsten Bartsch from University Hospital Schleswig-Holstein in Kiel, Germany and colleagues report.

The treatment was well tolerated and no stimulation-related side effects were observed.

Two patients did not show a treatment response, defined as a reduction in attack frequency or severity of at least 50 percent, and were viewed as treatment failures. One patient was attack free for 6 months before suffering cluster headache attacks again.

After an average follow up of 17 months, 3 of 6 patients remain "almost attack-free," the investigators report, yielding an overall response rate of 50 percent. "reason for the three long-term treatment failures in our series remains unclear," Bartsch and colleagues write.

They say further studies are needed to figure out which patients are most likely to respond to this therapy, gain a greater understanding of precisely how deep brain stimulation works, and to gather information on the long-term outcome in cluster headache patients