Understanding Recent Research on Deep Brain Stimulation and Walking

Edelle Field-Fote, PT, Ph.D., FAPTA, FASIA, director of spinal cord injury research and the Hulse Spinal Cord Injury Lab at Shepherd Center, is co-principal investigator in the Up-LIFT clinical trial.

Dr. Field-Fote Reviews Cho and colleagues. Hypothalamic deep brain stimulation augments walking after spinal cord injury. Nat Med. 2024 Dec;30(12):3676-3686. doi: 10.1038/s41591-024-03306-x.

Recently, researchers from Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and Lausanne University Hospital published findings in the journal Nature Medicine about how deep brain stimulation (DBS) helped two people with spinal cord injuries walk.

We spoke with Edelle Field-Fote, PT, PhD, FAPTA, FASIA, director of spinal cord injury research and the Hulse SCI Research Laboratory at Shepherd Center to better understand the researchers' process and what it could mean for people experiencing paralysis after sustaining a spinal cord injury.

Understanding the Impact of DBS on Spinal Cord Injuries

When a spinal cord injury occurs, the pathways between the brain and spinal cord motor neurons are disrupted, leading to varying degrees of paralysis or paresis and impaired motor function. Building on this understanding, researchers discovered that deep brain stimulation (DBS), targeting part of the brain called the lateral hypothalamus (LH), could improve lower-limb movements in individuals with incomplete spinal cord injuries.

Dr. Field-Fote describes the researchers' methods as "phenomenally wonderful in terms of a scientific approach, in terms of real-world application, it’s probably a ways off."

Breaking down their process, she noted they began with a lateral hemisection model, in which half of a rat's spinal cord is cut. This model preserves the descending pathways from the brainstem (where the hypothalamus is) to the spinal cord, enabling researchers to study the connections between these areas and the spinal neurons responsible for movement.

Promising Results

Rats with a hemisection are known to spontaneously recover some walking ability but retain significant difficulties, such as walking with a crouched gait. Furthermore, it is well known that when DBS was applied, the rats demonstrated a more normal walking pattern.

"While the results in the rat hemisection model were promising for the rats, this model is not very relevant to humans," Dr. Field-Fote explained. To address this, the researchers used a contusion model, which more closely mimics the type of damage seen in human spinal cord injuries. In this model, DBS alone was less effective, but combining stimulation with training improved walking outcomes for the animals.”

Transition to Human Trials

The researchers identified two individuals from prior studies who were willing to undergo surgery to implant electrodes in their brains. Both participants could already walk but experienced significant challenges. With stimulation, one participant progressed from needing body-weight support to walking without it, and the other, who previously could not climb stairs, gained the ability to do so.

While these improvements were significant, they were modest. Additionally, no comparisons were made to non-invasive methods, such as transcutaneous electrical stimulation, which is increasingly being used in therapy at facilities like Shepherd Center.

Explaining Electrical Stimulation

Dr. Field-Fote offered a helpful analogy to explain how stimulation works: "A damaged spinal cord is like a water hose with many holes. While some water reaches the flowers, much of it leaks out. If you turn up the water pressure, more water makes it to the flowers."

Similarly, electrical stimulation increases the excitability of motor neurons, allowing more signals to reach the muscles and improve movement.

In the Hulse Spinal Cord Injury Lab, Dr. Field-Fote's team focuses on increasing spinal cord activity using transcutaneous electrodes (electrodes placed on the surface of the skin), a non-invasive alternative to DBS. This method avoids the risks and invasiveness of brain surgery while achieving similar modest improvements in walking.

The Importance of Comparative Studies

While acknowledging that neither DBS nor non-invasive stimulation can fully reverse paralysis, Dr. Field-Fote emphasized the importance of this research for understanding brain-spinal cord communication. "This work helps us understand the organization of the brain and spinal cord and how they communicate with each other," she said.

Dr. Field-Fote hopes to see future comparative studies between DBS and transcutaneous stimulation. However, such studies face significant challenges. It is difficult to recruit participants willing to undergo invasive surgery. Additionally, the learning effect from training, which results in lasting improvements even after the intervention ends, complicates direct comparisons. This effect makes it hard to isolate the specific impact of each intervention.

A Step Forward in Spinal Cord Injury Research

Although DBS is not a cure for paralysis, this research represents an important step in advancing treatment for spinal cord injuries. The findings underscore the potential of electrical stimulation, whether invasive or non-invasive, to improve mobility and quality of life for individuals with walking impairments. Dr. Field-Fote and her team remain dedicated to exploring innovative approaches to spinal cord rehabilitation.

Interview by Dominique McPhearson