Potential protection against failed back surgery syndrome

Texas researchers believe that they have discovered how to prevent many cases of the most common problem encountered by patients undergoing spine surgery: failed back surgery syndrome (FBSS).

FBSS occurs when surgery either fails to cure back pain or leads to additional chronic pain after a spinal operation.

In experiments using laboratory rats, neuroscientists at the University of Texas Medical Branch at Galveston (UTMB) applied the local anesthetic Lidocaine to the animals' exposed spinal cords before subjecting the rats to simulated spinal surgery. They found the procedure prevented both the release of chemicals associated with FBSS and behavior typical of animals experiencing FBSS-caused pain.

A paper describing their investigation is in press at the journal Experimental Neurology, and is available at the journal's Web site in the "Articles in Press" section.

"Our hypothesis is that the unintentional stretching and compression that can occur in the spinal cord during surgery causes the release of large quantities of chemicals called excitatory amino acids, which produce a toxic environment in the spine and cause long-term hyperexcitability in spinal neurons, generating chronic neuropathic pain - pain produced in the nerves themselves," said UTMB neuroscience and cell biology professor Claire Hulsebosch, a senior author of the paper along with UTMB neuroscience and cell biology professor David J. McAdoo. "When we applied Lidocaine to the surface of the spinal cord before conducting our surgery," Hulsebosch continued, "we found that those releases were completely blocked."

In addition, Hulsebosch noted, rats whose spines had been pretreated with the local anesthetic showed less sensitivity and scored much lower than non-treated rats on a standard test for symptoms of neuropathic pain. In the test, steadily increasing pressure is applied to a rat's hind paws with fishing-line-like filaments. Rats experiencing the hypersensitivity associated with chronic pain tend to withdraw their paws at very low pressures, while those without chronic nerve pain react only to much higher pressures.

Researchers involved in the experiment cautioned that FBSS is a somewhat loose diagnosis, one with multiple causes that also may include pre-existing conditions that spinal surgery does not successfully address. "It also has to be said that the model we used, in which we cut the nerves in the dorsal root on the surface of the spinal cord, involved a severe injury," said UTMB neuroscience graduate student and first author Brian Rooney "But we think it's a good representation of the sort of injury that can be produced by surgery."