MONDAY, Jan. 31 (HealthDayNews) -- For years, damaged discs in the lower back or spinal nerve problems have taken the blame as the most common cause of sciatica, a painful condition in which the sciatic nerve in the back of the leg is pinched and pain radiates down the leg.
But a new study suggests the cause of sciatica pain may actually be piriformis syndrome, a condition in which a muscle in the buttocks called the piriformis compresses or irritates the sciatic nerve.
The study appears in the February issue of the Journal of Neurosurgery: Spine.
The findings may help many patients finally get relief from their pain, said study author Dr. Aaron Filler, a neurosurgeon at Cedars-Sinai Institute of Spinal Disorders in Los Angeles. "Doctors often recommend spinal fusion surgery for spinal problems [associated with sciatica]," he said, "when the real problem is piriformis syndrome."
In the study, Filler and his colleagues evaluated 239 patients whose symptoms of sciatica had not improved after diagnosis or treatment for a damaged disc. They performed the usual X-rays and MRI scans, and found seven of the patients had torn disc-related conditions that could be treated successfully with spine surgery.
The other 232 patients underwent MR neurography, a new technique that generates detailed images of nerves. The researchers report that 69 percent had piriformis syndrome, while the other 31 percent had some other nerve, joint or muscle condition.
To treat piriformis syndrome, Filler's team injected a long-acting anesthetic into the spine, muscle or nerve areas. About 85 percent of the patients got some relief from the injections, which helps relax muscle spasm. However, relief was not long-lasting and 62 patients needed surgery to correct the syndrome. Of those, 82 percent had a good or excellent result during the six-year follow-up.
The findings may help legions of Americans suffering from sciatica, Filler said. "More than 1.5 million Americans have experienced sciatica severe enough to be sent for lumbar MRI scanning each year," Filler said. "About 300,000 lumbar disc surgeries are done each year for sciatica. Of those, about one-third fail."
In some cases, those surgeries may fail because disc damage is not the underlying problem, Filler said. Instead, the real culprit could be other conditions, such as piriformis syndrome.
The nerve scan used in the study is relatively new, Filler said, being first used in humans in 1993. His group reported on the first groups of patients who underwent the technique in 1996. "Since 1996, we have imaged several thousand patients," he said. The technique is available now at major universities and hospitals, Filler said, and is expected to become more widespread in the next year or so.
While the study provides new clues to sciatica, experts say its results need to be duplicated. When patients complain of sciatica, "we typically focus on spinal nerves," explained Dr. Scott M. Fishman, president-elect of the American Academy of Pain Medicine.
"This study helps clarify that pain that radiates down the back of the leg is often of sciatic origin," Fishman said, and doctors should consider the possibility that the pain may be due to entrapment of the sciatic nerve by the piriformis muscle.
"Piriformis syndrome is pooh-poohed [as a diagnosis] by orthopedic surgeons and neurosurgeons," added Dr. Peter Slabaugh, a spokesman for the American Academy of Orthopaedic Surgeons. But the new findings, he said, "might have some merit," although he said more studies with similar results are crucial before firm recommendations can be made.
Those with sciatica should also know that the pain typically comes and goes, Slabaugh said. Unless symptoms are very severe, waiting three months after the pain starts before undergoing serious treatments such as surgery is usually sound advice, he added.
If the pain doesn't subside after three months, patients would be wise to then consider imaging studies of the spine and nerves, he added.
To learn more about piriformis syndrome, visit the National Institute of Neurological Disorders and Stroke.
SOURCES: Aaron Filler, M.D., Ph.D., neurosurgeon, Cedars-Sinai Institute of Spinal Disorders, Los Angeles; Scott M. Fishman, M.D., president-elect, American Academy of Pain Medicine, and chief, division of pain medicine, University of California, Davis; Peter Slabaugh, M.D., Oakland, Ca., orthopaedic surgeon and spokesman, American Academy of Orthopaedic Surgeons; February 2005 Journal of Neurosurgery: Spine ~BACH~~NERV~~NEUR~~PAIN~