Peripheral Nerve Injuries Require Timely Diagnoses

After a traumatic nerve injury, there is an 18-month window for nerves to recover on their own, or with surgical intervention, research shows. After that, the regenerative potential of both the injured nerve and the affected muscle tissue decreases.

"That's why by about six weeks after the injury, it is important to assess for early signs of recovery," says neurologist John Engstrom, M.D., of the Nerve Injury Clinic at UCSF Medical Center. Absent an expert diagnosis, a wait-and-see approach can subject the patient's full recovery to unnecessary risk.

Ideally, diagnosis and treatment occur at a clinic equipped to deal with everything from a bruised single nerve in a limb to an avulsion of the brachial plexus. An initial evaluation by the neurologist could include electromyography and, perhaps, referral to a radiologist for magnetic resonance neurography.

"We need first to confirm that it is a nerve injury and not something like a severed tendon," Engstrom says. One of the advantages of a multidisciplinary clinic is that neurologists and neurosurgeons work closely with radiologists and orthopedists to verify nerve injury severity and location.

Once nerve damage is confirmed, "the injury mechanism affects our thinking about the potential for regeneration," says neurologist Jeffrey Ralph, M.D., says.

"There are various ways a nerve might repair itself and each has its own time frame," Engstrom says. "But other factors affect the process, including patient age, medical conditions that affect nerve repair such as diabetes and distance between the site of nerve injury and the target muscles. The question is how to weigh those factors to determine when to let the system heal itself and when to graft nerves to the injury site."

"After an initial assessment, we typically see patients every two to three months to assess whether regenerating nerve fibers have reached target muscles," Ralph says. "Paresthesias can occur at the leading edge of axonal growth and sometimes indicate whether the nerve is regenerating fast enough to avert surgery."

"If the nerve will not heal itself in time, the repair involves removal of the damaged segment and nerve grafting," neurosurgeon Nicholas Barbaro, M.D., says. For the grafting, he uses either collagen tube implants or a sensory nerve from the leg.

Post-treatment, the team reevaluates patients regularly. The multidisciplinary approach enables them to provide advice on everything from neuropathic pain management to physical therapy, occupational therapy and orthotics.

"The key message is that the window for recovery closes quickly, so physicians who suspect nerve injury should not wait to refer their patients," Barbaro says.

For more information, contact the Nerve Injury Clinic at (415) 353-7500.

Imaging the Nerve Becomes a Critical Diagnostic Tool

Magnetic resonance neurography (MRN) — an MRI of the nerves — demonstrates the location and severity of nerve injuries, according to radiologist Cynthia Chin, M.D., and her colleagues at the Nerve Injury Clinic at UCSF Medical Center. Advanced imaging techniques and knowledge of nerve anatomy allow visualization of abnormal nerves in ways that were not possible before.

"We can visualize if the nerve is injured by detecting edema," Chin says. "We can evaluate if the nerve is intact, avulsed or transected and help to direct surgical intervention. We can also provide evidence of post-traumatic neuromas."

Neuroscience — Winter 2008 Table of Contents

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