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Stroke patients may benefit from brain stimulation

A single DBS lead is implanted into the cerebellum, with nerve fibers extending from the implant region through the thalamus and into the motor cortex. Cleveland Clinic Foundation

Stroke is a leading cause of death and serious long-term disability in the United States. About half of those who survive a stroke are left with ongoing impairments that affect their everyday activities, such as walking or lifting objects. Physical therapy can help to improve movement and reduce symptoms. But its benefits often level off about a year following the stroke.

Scientists have been exploring the possibility of encouraging the brain to form new connections between nerve cells by using electrical stimulation. The approach, called deep brain stimulation, delivers constant electrical stimulation to a particular brain region through a surgically implanted thin wire, or electrode.

A research team co-led by Drs. André Machado and Kenneth B. Baker of the Cleveland Clinic targeted a brain region called the dentate nucleus. It lies within the brain’s cerebellum, in the lower back of the head. The cerebellum is known to play a role in coordinating muscle movements. Decades of animal studies have shown that the dentate nucleus is a key connector that helps link the cerebellum to the motor cortex, which controls voluntary movements.

In a phase 1 clinical trial, the team enrolled 12 people who had moderate to severe impairment of their upper limbs one to three years after a stroke. At the start of the study, participants engaged in a month of physical therapy twice a week to rule out possible recovery based on physical therapy alone. Each then underwent surgery to insert the electrode in the brain’s dentate nucleus. After a recovery period, physical therapy continued, and deep brain stimulation was delivered continuously for four to eight months. Results were reported in Nature Medicine on August 14, 2023.

The researchers found that their technique of combining deep brain stimulation with physical therapy was safe. No serious adverse events or device failures were noted. Nine of the 12 participants had improved motor function after the treatment. These improvements continued even after stimulation was turned off.

Importantly, the length of time since a patient’s stroke did not seem to affect the potential for improvement. But the level of motor function in the hand did seem relevant to recovery. Participants who had retained some level of motor function in the hand had clinically significant improvement. Those with a low level of motor function showed only minor gains.

“The results of the study found that deep brain stimulation, paired with physical therapy, improved movement in patients who were more than a year out from their stroke and whose motor improvements had largely plateaued,” Baker says. “This tells us the research warrants further investigation in larger patient samples.”