Nerve-switch surgery restores function of paralyzed arms in small study

By Gene Emery

(Reuters Health) - - Doctors in Shanghai say they have made paralyzed arms useful again by surgically swapping a nerve coming out of the spinal cord.

A year after the surgery, "the paralyzed arm showed improved power, function and reduced spasticity," they report in The New England Journal of Medicine.

But the small study is sparking skepticism because the improvements seemed to appear faster than nerves are typically able to grow.

Dr. Robert Spinner, chairman of neurosurgery at the Mayo Clinic in Rochester, Minnesota, said it's possible the benefits were caused by simply cutting the bad nerve leading to the affected arm, a much simpler procedure than the nerve transfer surgery.

"These results are very exciting because this is a very big problem in America and the world. The question really is, what's causing the effect," he said in a telephone interview. "To cut the bad wire would be a lot easier than doing their procedure."

The senior author of the study, Dr. Wen-Dong Xu of Fudan University, did not respond to emailed questions.

The randomized trial involved 36 men at Huashan Hospital, all of whom had at least some muscle power and the ability detect touch. Their paralysis was due to brain injuries including strokes, cerebral palsy and head trauma. On average, patients had been paralyzed for 15 years and had undergone 10 years of rehabilitation.

In 18 patients, surgeons found a nerve feeding the affected arm - the C7 nerve, which exits the spine at the base of the neck - and severed it near the spinal cord. The C7 accounts for about 20% of the nerve impulses going into an arm.

Then, on the other side of the spinal cord, surgeons cut the healthy C7 nerve feeding the unaffected arm, rerouted it behind the esophagus, and grafted it onto the nerve leading to the affected arm. The hope was to give control of the paralyzed arm to a healthy part of the brain.

The other 18 volunteers simply received the same four-times-per-week rehabilitation regimen that the surgery group did.

On a 67-point movement scale, the surgery group collectively started at 29.0 points and ended at 46.7 after 12 months. Volunteers in the rehabilitation-only group went from 29.1 points to 31.7 points.

Before surgery, none of the patients could reach or grasp with the paralyzed hand, and none could dress, tie shoes, wring out a towel, or operate a mobile phone with the affected arm and hand, researchers reported.

After surgery, 16 of the 18 could perform at least three of those tasks. None of the rehabilitation-only patients could.

There were side effects. Twelve patients in the surgery group reported a strange feeling while swallowing and 15 reported fatigue. In the healthy arm that originally got signals from the C7 nerve, hand numbness was reported by 16 people, 16 said they couldn't extend their wrists with as much force as they could before, 15 said they couldn't extend their elbow as forcefully as before, and 16 reported lessened sensory function. The side effects often subsided over time.

The Xu team acknowledged that just severing the nerve leading to the paralyzed arm may have helped release the spasticity, making rehabilitation easier. But they said there was evidence that nerve cells were reconnecting the brain to the arm.

The results “are exciting but need clarification and confirmation," Spinner and two colleagues wrote in a Journal editorial.

They noted that nerves usually grow an inch per month, so 12 months would not be enough time to make a direct connection from the spine to the hand.

"Nerves do not regenerate that quickly, fully, or consistently," they said.

It's more likely that cutting the nerve produced the benefits by stopping the hand and arm muscles from spasming, allowing other nerves that move the arm to work more effectively, Spinner believes.

One way to test that would be to just cut the C7 nerve and see if that is enough to produce the improvements, he said.

"In their paper they say they saw some improvements after one month,” Spinner noted. “Certainly that can't be from regeneration. Usually full results from long-distance regeneration take several years."

SOURCE: The New England Journal of Medicine, online December 20, 2017.

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