Lay summary by Frank Yeung
Edited by Crystal Han
This lay summary is based on the research paper by Fatma Inanici, Lorie N Brighton, Soshi Samejima, Christoph P Hofstetter, Chet T Moritz. Read the original article here.
What is transcutaneous electrical spinal cord stimulation?
When spinal cord injuries occur, individuals may lose their ability to move certain limbs (motor function) and to control blood pressure, bladder and bowel (autonomic function)l. The current treatment for these disabilities is exercise therapy, which aims to help the person recover some degree of motor function. This method’s outcomes are usually limited, so researchers are keen on finding more effective therapies to help restore motor and autonomic function.
Regaining arm and hand functions are a higher priority than the lower limbs, because we require our upper limbs to perform many daily tasks. Unfortunately, current clinical practice has hardly any approaches for restoring upper limb function and their outcomes are inadequate. In this study, a team of five researchers from the University of Washington through the collaboration with University of California, Los Angeles, decided to investigate a novel approach involving transcutaneous electrical spinal cord stimulations. Transcutaneous means above the skin, making this a non-invasive procedure.
Transcutaneous electrical spinal cord stimulations are non-invasive because the electrical stimulation is given above the skin. This technique using a unique high frequency waveform allows application of high current intensities through the skin that can reach the spinal cord without causing discomfort but still be able to activate spinal networks. The researchers reported that the stimulation was well tolerated by participants, and there were no significant adverse events. In this study, they aimed to use this technique to enable movement such that the paralyzed individual can participate in intensive exercise training programs and achieve long term recovery of function.
How was the research conducted?
The researchers recruited six volunteers with chronic cervical spinal cord injuries. These people have become paralyzed or have limited ability to move their limbs and fingers. The study started by having the participants train in an upper extremity motor task three times per week for four weeks. Each session was two hours long, and they performed tasks involving the whole limb or just the fingers, and they may use one or both hands. For instance, they may flex their elbow, squeeze TheraPutty with their hand, or pinch a coin with their fingers. The tasks got progressively harder as the participants improved. To illustrate, they may decrease the coin’s size for the pinch task.
After the four weeks, the participants had a total eight weeks of transcutaneous electrical stimulation to the spinal cord, using an experimental device approved by the University of Washington. This was paired with the same motor training for another eight weeks to compare how much the participants improved during this time span compared to the motor training alone.
To ensure improvement in motor function, stimulation intensity was adjusted based on feedback from the participants about which intensity made the task easiest. It is key that the stimulation does not cause direct muscle contractions, but rather help the participant enhance control over their muscles, hence making the task feels easier. They also tried different types of simulations, such as monophasic and biphasic stimulation, to see how it affects their improvement. In general, monophasic stimulation facilitated activities that require strength, whereas biphasic stimulation promoted fine motor skill.
Lastly, the researchers followed the participants for three months after the last treatment to see if improvements made during therapy were maintained. This is important for achieving long term recovery of function. In other words, they hoped that the patient’s improvements will last, and they will not need the electrical stimulations and training anymore.
What are the findings and why are they important?
The study has found that transcutaneous electrical stimulation of the spinal cord leads to rapid and sustained recovery of hand and arm function, even after complete paralysis. It also led to some anecdotal improvements in autonomic function, such as heart rate regulation. The effects lasted at least three to six months beyond stimulation, indicating that the nervous system has adapted and facilitated long term recovery of function.
They helped two participants with no functional finger and thumb movement in the beginning of the study regain their ability to move their fingers and thumb by the end. Specifically, the training paired with stimulation helped them pinch and increase the pinch force. They can pinch hard enough to press remote control buttons or open a vertical zipper.
The other four participants had limited ability to move their fingers and thumbs in the beginning, and training and stimulation helped them regain a high level of hand function, including grasping objects. Stimulation had immediate effects on them as opposed to the previous two participants.
One participant reported that his heart rate was restored to normal, and they regained the ability to sweat below the injury level. Others reported that it reduced muscle spasms, allowing them to perform activities better and have higher quality sleep due to the relief of nighttime spasms. Another two were able to improve their bladder control. Two also mentioned that their core stability, balance, and lower extremity function improved. These are anecdotal findings but still all allowed them to enjoy a higher quality of life. Several were able to resume their hobbies, such as painting. Most impressively, the improvements were maintained for at least three to six months after the stimulation and training.