About six weeks ago, a glass shattered in my hand, severing the nerve in my pinky finger. The feeling in my fingertip still hasn’t returned, and now I know why: I’m too old.
Going back to World War II, it’s been speculated that recovery of peripheral nerve injuries—like those in limbs and extremities—is influenced by age. And studies indicate that peripheral neuropathy is common in people over 65, including those who have received cancer chemotherapy, and often unexplained.
“When you’re very young, the system is very plastic and able to regenerate,” Michio Painter told me recently. He is a graduate student in the laboratory of Clifford Woolf, PhD, director of the F.M. Kirby Neurobiology Center at Boston Children’s Hospital. “After that, there’s a gradual decline. By the age of 30, much of this plasticity is gone.”
Traditionally, this decline has been thought to reflect age-related differences in neurons’ ability to regrow, but when Painter studied neurons in a dish, he couldn’t confirm this. …
It’s common in medicine for physicians to “wait and see” before taking treatment to a more invasive (or expensive) level. But when it comes to motor nerve injuries, combined laboratory and clinical evidence suggests that approach may be fundamentally wrong.
That would go for injuries including carpal tunnel syndrome, cubital tunnel syndrome (a compression injury of the ulnar nerve in the elbow), nerve damage from surgery or chemotherapy, and brachial plexus avulsion injuries (these often happen when people fall off their bikes; the arm is bent backwards and nerves get ripped out of the spinal cord).
In serious cases, patients may recover sensory function, but rarely recover full muscle function and strength. Lab studies by neuroscientists at Children’s Hospital Boston provide a biological explanation, and therein may lie a solution.
It’s not that injured motor nerve fibers don’t regrow – they can. It’s that they don’t grow fast enough. …