112 Journal of Manipulative and Physiological Therapeutics Volume 23 • Number 2 • February 2000 0161-4754/2000/$12.00 + 0 76111104082 © 2000 JMPT Neurologic Effects of the Adjustment Scott Haldeman, DC, MD, PhD" ABSTRACT This paper discusses the several theories pertaining to the chiropractic adjustment, in- cluding the nerve compression theory, reflex theories, and pain relief theories. There is now sufficient scientific research to consider these theories reasonable working models to explain the effects of the adjustment but insufficient to consider them valid. (J Manipulative Physiol Ther 2000;23:112-4) Key IndexingTerms: Chiropractic; Neurology; Pain INTRODUCTION • During the course of the World Chiropractic Congress in Auckland, New Zealand, much scientific evidence was pre- sented in the field of spinal neurophysiology, which helps to form the basis for chiropractic theory and philosophy. There were also many panel discussions and workshops in which both traditional and modem theories on the pathophysiology of the subluxation and the effects of the adjustment on the nervous system were reviewed. It would be difficult to find a more learned and comprehensive panel of speakers or a more detailed discussion of the topic anywhere else in the world. Listening to the scientific presentations and the philo- sophic panels, a number of issues became evident. First, there was an attempt by the scientific community to make their research meaningful by suggesting that this research be used as a logical clinical mechanism to explain the effects of the adjustment. There was a presumption by the philoso- phers and clinicians that the research was conclusive and could be used to justify the various theories on the patho- physiology of the subluxation. Close scrutiny of the data and the debate demonstrated the tenuous connection between the scientific research and the philosophic theories. A significant leap of faith is required to accept and present a convincing argument about the various theories on the neurologic effects of the adjustment. DISCUSSION The Principlesof Neurologic Theories of the Adjustment In 1977, at a conference sponsored by the National Insti- tute of Neurological and Communicative Disorders and Stroke on "The Neurobiological Mechanisms in Manipula- tive Therapy," I was asked to present a paper titled "The Clin- ical Basis for Discussions of Mechanisms of Manipulative Therapy ''l to put the meager research available at that time in perspective. The basic criteria for judging a proposed neurobiologic mechanism of manipulation was laid out. Four criteria were presented. Criterion I stated that a specific ma- nipulative procedure must demonstrate consistent clinical re- suits under controlled conditions in the treatment of a specific pathologic process, organ dysfunction, or symptom complex. Criterion H stated that the specific manipulative process must demonstrate" a specific effect on the musculoskeletal system to which it is applied. Criterion III stated that the muscu- loskeletal effect caused by the manipulation must be shown to have a specific influence on the nervous system. Criterion IV stated that the influence on the nervous system brought about by the manipulation must demonstrate a beneficial in- fluence on abnormal function of an organ, tissue pathology, or symptom complex. These criteria are illustrated in Fig I and remain as valid today as they were in 1977. Examining the current research and theory objectively requires determination of the strengths and weaknesses of each proposed neurologic effect of the adjustment. aClinical professor, Department of Neurology, University of California-Irvine, and adjunct professor, Research Department, Los Angeles Chiropractic College. Submit reprint requests to: Scott Haldeman, DC, MD, PhD, Clin- ical professor, Department of Neurology, University of California- Irvine, 1125 E 17th St, Ste W127, Santa Ana, CA 92701. Paper submitted June 29, 1999. Nerve Compression Theories for the Adjustment The predominant theory on the effect of the adjustment is based on the concept of nerve compression. This theory pro- poses that the primary effect of the adjustment is to correct a subluxation. Subluxation is defined as an abnormal biome- chanic relation among vertebrae that can cause compression