“This is very interesting,” said Jason Carmel, a motor system neuroscientist at Columbia University who was not involved in the study. “It opens up a treatment pathway for people with chronic stroke that we’ve never had before.”
Stroke is the most common cause of disability in adults. Globally, one in four people over the age of 25 will suffer from one in their lifetime, and three-quarters will have permanent motor impairment in their hands and arms.
A stroke occurs when the blood supply to the brain is blocked or a blood vessel bursts. Depending on the severity of the brain damage and where it occurs, a stroke can cause certain disabilities, such as paralysis, weakness, or difficulty speaking, thinking or remembering.
People paralyzed by stroke cannot move a particular muscle or group of muscles voluntarily. When the part of the brain that controls movement is damaged, messages between the brain and muscles are disrupted. Patients who recover often do so within the first few months after having 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 at this stage, and researchers wanted to see if they could use mild electrical currents delivered to specific areas along the spinal cord to restore hand and arm muscle function. The spinal cord is a long nerve tube in the back that carries messages from the brain to the rest of the body.
Spinal cord stimulation is used for pain relief. In 2018, different research groups published a series of papers showing that a handful of patients paralyzed by spinal cord injuries were able to stand independently and walk for the first time with assistive devices. years. However, spinal cord stimulation for upper limb rehabilitation has not been widely investigated.
In the latest study, surgeons implanted a pair of thin metal electrodes shaped like spaghetti noodles into the upper part of the spinal cord in the neck to target the nerves that control hand and arm muscles. Electrode cables were removed from the skin and connected to the stimulation system in the laboratory.
On the day researchers turned on the electrical stimulation, Rendulich was able to fully open and close her left hand – something she had never been able to do before. “We were all in tears,” she says. “I’ve been opening my arms like I haven’t in ten years.”
Over four weeks, Rendulic and the other patient underwent a series of laboratory tests. (The second patient, a 47-year-old woman with severe impairment, had a stroke three years earlier.) They performed tasks such as moving blocks, picking up marbles, holding a container of soup, and opening a lock. Although Rendulic showed more improvement than the other patient, the stimulation improved strength, mobility, and arm and hand function in both women. Rendulich said she could feel a slight vibration in her hand when the device was turned on, but it didn’t hurt.
