Spinal cord injury (SCI) disrupts the communication pathway between the brain and the nerves that control muscles to produce movement, typically leaving the planning, coordination and effector centers above and below the injury functional. One promising avenue of research is focused on creating new pathways for signal transmission between the brain and the rest of the body.
Researchers at Mayo Clinic's campus in Rochester, Minnesota, are exploring the use of electronic devices that can wirelessly transmit signals from the brain to the intact spinal cord circuitry below the injury. In this novel approach, injured nerves are bypassed with electronics. Although this field of research is in its early stages, the prospects are intriguing.
Worldwide, several different stimulation modalities for activating muscle have been tested in both animal models and humans, including transcutaneous stimulation, percutaneous stimulation, intramuscular stimulation and peripheral nerve stimulation; however, none of these techniques has experienced widespread clinical translation.
Mayo researchers are currently exploring the therapeutic use of electrical stimulation within the spinal cord, termed intraspinal microstimulation (ISMS), as a means to provide neuromuscular activation to restore function in paralyzed limbs. ISMS involves the implantation of stimulating electrodes within the ventral gray matter of the spinal cord to activate motor circuitry.
"Over the past 15 years, multiple studies have demonstrated that ISMS can successfully and safely evoke coordinated limb movement and weight bearing in rodent and feline models, while overcoming some of the limitations, such as the rapid onset of muscle fatigue during stimulation, that accompany conventional stimulation techniques," explains Mayo Clinic neurosurgeon Kendall H. Lee, M.D., Ph.D.