“This is very exciting,” said Jason Carmel, a motor neuroscientist at Columbia University who was not involved in the study. “It opens up a potential treatment avenue we’ve never had before for people with chronic stroke.”
Stroke is the most common cause of disability in adults. Worldwide, one in four people over the age of 25 will get one in their lifetime, and three quarters of them will have permanent motor impairment in their arm and hand.
A stroke occurs when blood flow to the brain is blocked or when a blood vessel bursts. Depending on the severity of the brain damage and where it occurs, a stroke can cause certain disorders, such as paralysis, weakness, or problems with speaking, thinking, or memory.
People with paralysis from a stroke are unable to voluntarily move a particular muscle or muscle group. When the part of the brain that controls movement is damaged, it disrupts the transmission of messages between the brain and the muscles. Patients who recover often do so in the first few months after a stroke. After six months there is little chance of further improvement. This is the chronic stage of stroke, when the effects are usually permanent.
Both Rendulic and the other patient were in this phase, and researchers wanted to see if they could use a mild electrical current delivered to precise locations on the spinal cord to restore function to the arm and hand muscles. The spinal cord is the long tube of nerves in the back that transmits messages from the brain to the rest of the body.
Stimulation of the spinal cord is already used as a pain treatment and in 2018 different research plow published a series of papers showing that a handful of patients paralyzed by spinal cord injuries were able to stand and walk independently with assistive devices for the first time in years. But spinal cord stimulation for upper extremity recovery is largely unexplored.
In the latest study, surgeons implanted a pair of thin metal electrodes resembling spaghetti noodles along the upper part of the spinal cord in the neck to target nerve populations that control the arm and hand muscles. The electrode leads were passed outside the skin and connected to a stimulation system in the lab.
On the day researchers turned on the electrical stimulation, Rendulic was able to fully open and close her left hand, something she couldn’t do before. “We were all in tears,” she says. “I opened my hand in ways I hadn’t in nearly a decade.”
For four weeks, Rendulic and the other patient performed a series of lab tests. (The second patient, a 47-year-old woman with more severe abnormalities, had suffered a stroke three years earlier.) They performed tasks such as moving blocks, picking up marbles, grabbing a soup can, and opening a lock. Although Rendulic showed more improvement than the other patient, the stimulation increased strength, range of motion, and function of the arm and hand in both women. When the device was on, Rendulic said she could feel a slight vibration in her arm, but it didn’t hurt.