(The Associated Press) - Injecting a steroid directly into the spine can ease the debilitating pain of shingles when nothing else helps, a Japanese study has found.

Patients who got a steroid-anesthetic mixture reported that the extent and severity of their pain was reduced by more than 70 percent - and that the relief was lasting, researchers at the University of Hirosaki School of Medicine report.

Those who got the anesthetic alone did little better than a comparison group that got no extra treatment at all, Dr. Naoki Kotani wrote in Thursday's issue of the New England Journal of Medicine (news - web sites).

All of the patients had suffered for at least a year with pain that did not yield to any other treatment.

The two treatment groups got a series of four injections, of either the anesthetic lidocaine or a mixture of lidocaine and methylprednisolone. They were checked four months, one year and two years later.

The pain reduction lasted the whole two years, Kotani wrote.

``I was surprised by how large the relief they got was and how sustained it was,'' said Dr. Michael Rowbotham, an associate professor of neurology at the University of California at San Francisco.

He said he would like to see a large U.S. or European study of the treatment.

``The results that they got are so dramatic that it'll be very important to see this work replicated. Because the magnitude of the reductions in pain are really greater than with any of the current treatments.''

The study excluded one of the most common sites of shingles pain: the face. If the pain was in the neck, chest or back, the treatment table was tilted to a head-down position immediately after the injection. Those with abdominal or lower body pain were kept horizontal.

Anyone who has had chickenpox may develop shingles. Some of the virus, called herpes zoster, survives and can turn active again.

This causes the pain and rash of shingles. Most people recover completely. But in about one-fifth of cases, the virus damages nerves in certain parts of the skin, causing severe pain that can last for years. It may be a deep ache, a burning pain, sharp jabs, or even feel like an electric shock. In addition, skin can become so sensitive that even a slight change in temperature or the brush of hair against skin is painful.

Kotani looked at people who had both severe pain and hypersensitive skin.

Four weeks after the last shot, only six of the 91 patients who got lidocaine alone and only four of 90 non-treated patients said their pain was reduced by more than half. But 82 of the 89 patients who got the steroid-anesthetic mix reported that their pain was reduced by more than half - and those results lasted the full two years. The seven who got less relief had been in pain for more than five years, Kotani reported.

``It seems that patients with really longstanding pain were not likely to benefit. That's unfortunate,'' Rowbotham said.

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