Electrical Stimulation to Partially Restore Mobility to Paralysis Patients

I had the opportunity to do an internship at the Functional Electrical Stimulation (FES) Center in Cleveland, OH. The FES Center is supported by two hospitals and Case Western Reserve University. The FES Center specializes in helping restore muscle function and control to paralysis patients. We had a patient who had been shot in the back of the neck severing most of her spinal cord in between the C1 and C2 vertebrae. She was paralyzed from the shoulders down and had some control of her left shoulder, left arm, and left hand. Since she could still control her neck muscles and partially control her left shoulder this allowed researchers at the FES Center to design her a system to partially restore daily functions.

Surgeons implemented EMG sensors in her platysma, neck, and left shoulder muscles. Surgeons also implemented nerve cuffs that surround single nerves. She also has a bundle of wires coming out of the abdomen that could plug into an external control unit (ECU) that was used to test and make adjustments to her system. Her system utilized the EMG recording in her muscles in combination with an algorithm to electrically stimulate nerve cuffs which would cause action potentials down certain nerves and cause muscles to contract.

For instance when she would slightly mover her left shoulder forward, the EMG sensors would record the activity in the left trapezoid muscle causing electrical stimulation of a nerve cuff that causer her right tricep to contract, which would cause her to extend her right arm. If she made a frown this would induce the platysma muscles and cause her right forearm and hand muscles to contract and make a fist. A different muscle contraction in the neck or face area would cause her right bicep to contract causing her right arm to flex back towards her body. This FES system in her body is not sophisticated enough to alter the magnitude of the electrical current sent to her nerves so unlike a normal person her muscles would completely contract making her either fully extend or fully flexed in a very robotic motion, and this is all done with her seated in her wheelchair.

Even though there is major limitations this does allow her to eat and drink with limited help and is big gain for daily activities for paralysis patients. The technology of using electrical stimulation to bypass an injured spinal cord and innervate paralyzed muscles has actually been around for about twenty years and is used in different parts of the body. It is used in the legs to help stand or keep standing and also in muscles to help in bladder control and swallowing. The FES Center also specializes in prosthetics and neural engineering that gives a futuristic feel. They are currently researching and have tested on primates what they call neuromotor prosthesis. They are attempting to use a brain implant and sensors to detect the intent to move directly from the brain to control prosthetics or use nerve cuffs to stimulate paralyzed limbs.

http://fescenter.org/index.php

Kirsch, R. Development of a neuroprosthesis for restoring arm and hand function via functional electrical stimulation following high cervical spinal cord injury.

Kirsch, R. Toward the Restoration of Hand Use to a Paralyzed Monkey: Brain-Controlled Functional Electrical Stimulation of Forearm Muscles.