History of Spinal Cord Stimulation

Surgical Procedures for Pain Control

Surgical procedures for pain control may be considered as falling into one of three categories: anatomic, ablative, or augmentative ( ). Anatomic procedures address an abnormality presumed to be the cause of a complaint of pain, e.g., a herniated disc compressing a nerve root. Ablative procedures, e.g., rhizotomy or cordotomy, attempt to block transmission of pain by removing the neural substrate. Augmentative or neuromodulation procedures attempt to interfere with pain transmission by modulating the function of the intact nervous system. For 50 years spinal cord stimulation (SCS) has been the most common augmentative/neuromodulatory procedure using a device implanted surgically for chronic use ( ).

Historical Uses of Electrical Stimulation

Electrical stimulation has been used for medical purposes, particularly the relief of pain, for more than 5000 years. In 3100 BC the King Narmer papyrus highlighted using the electricity-emitting Nile catfish for pain control, and in the first century AD Scribonius Largus described the use of another bioelectric generator, the torpedo fish ( ). As artificial methods of generating electricity were developed in the 17th and 18th centuries, medical applications were prominent and a number of well-known historical figures were involved: Galvani, Volta, Franklin, Faraday, Duchene de Boulogne, Kratzenstein, Antoine Louis, Sherrington, Adrian, and others. In the late 1800s and early 1900s electrical stimulation devices were marketed for the treatment of pain, among other ailments, but this met with limited success in the absence of an accepted scientific rationale.

The Gate-Control Theory of Pain

The modern era of electrical stimulation for pain relief dates to the publication of the “gate theory” in by Melzack and Wall. The balance of activity between large and small fibers in the peripheral nervous system, according to this theory, determines whether pain is signaled centrally. An excess of small-fiber activity will open, and an excess of large-fiber activity will close, a metaphorical “gate” in the dorsal horn of the spinal cord. As large fibers in a mixed peripheral nerve have a lower threshold than small fibers for depolarization by an externally applied electrical field, stimulation at the appropriate amplitude can selectively activate the large fibers, closing the “gate.”

Peripheral Nerve Stimulation

Dr. William Sweet, then chairman of the Department of Neurosurgery at Massachusetts General Hospital, collaborated with Wall in a series of experiments with direct stimulation of peripheral nerves, beginning in October 1965. The resulting report, “Temporary Abolition of Pain in Man,” was published in Science in 1967 ( ). This work involved percutaneous placement of needle electrodes to study the effects of stimulation on acute as well as chronic pain. Chronically implanted peripheral nerve stimulation devices remain particularly useful for a subpopulation of patients with otherwise intractable pain in the distribution of a single peripheral nerve.

Dorsal Column Stimulation

One of the physicians who had worked with Sweet in Boston, C. Norman Shealy, became the first to implement the concept of electrically stimulating the spinal cord in humans. The dorsal columns of the spinal cord contain large-diameter primary afferents—the same neurons that may be recruited selectively in a mixed peripheral nerve because of their lower threshold for depolarization. In the spinal cord these fibers are conveniently segregated from motor fibers in an accessible location. Electrical stimulation of the dorsal columns of the spinal cord, it was reasoned, can have equivalent effects to peripheral nerve electrical stimulation and should address pain problems in the distribution of multiple peripheral nerves or segments on both sides of the body.

The first “dorsal column stimulation” (DCS) implant, later termed SCS, was performed 50 years ago, on March 24, 1967, and reported by Shealy later that year ( ). After his 1-year fellowship in Boston with Professor Sweet ended in 1963, Shealy had joined the neurosurgery faculty at (now Case) Western Reserve in Cleveland, where he collaborated with biomedical engineers Thomas Mortimer and James Reswick. Mortimer, a graduate student at the time, wrote his PhD thesis on the development of animal models, followed by successful clinical application of devices he designed and built ( ). The first use of DCS reported by Shealy was a cancer patient whose pain was relieved through implantation of an intradural but extramedullary electrode via high-thoracic laminectomy.