Spinal learning: central modulation of pain processing and long-term alteration of interneuronal excitability as a result of nociceptive peripheral input.

The influence of nociceptive peripheral input on the response characteristics of spinal interneurons may result in long-term alterations of interneuronal excitability and modify their responses to subsequent stimuli. Such neuromodulation has been found to result in physiological changes including hyperalgesia, lowering of pain thresholds, expansion of receptive fields and changes in response behaviors of muscles. These types of alterations may contribute to clinically significant findings including muscle spasm, hypomobility, edema, chronic pain, recurrences in areas of previous injury and resistance to treatment. This article reviews studies concerning plasticity of response behaviors of interneurons including habituation, spinal learning, spinal fixation, neuromodulation and the effects of substance P. Potential clinical and chiropractic application are discussed and a brief review of clinically relevant studies of chiropractic adjustments are cited.

Normal paraspinal tissue compliance: the reliability of a new clinical and experimental instrument.

Test-retest reliability of a hand-held tissue compliance meter was evaluated in 20 normal subjects at four paraspinal locations to determine possible effects of probe response or other sources of variability on measurements taken 10 min later at exactly the same location. If tissue compliance, as measured by this instrument, is to be used in a pre-post context to evaluate treatment effects, caution is urged, since 26% of the sites were significantly (+/- 1.96 SD) different on 10 min retest though subjects remained supine and without intervention. In addition, since 85% of these normal subjects displayed at least one paraspinal compliance asymmetry large enough to qualify as pathological by Fischer's criteria, revision of these criteria may be appropriate, at least for these paraspinal locations.

Effects of altered afferent articular input on sensation, proprioception, muscle tone and sympathetic reflex responses.

The influence of afferent articular and periarticular input on muscle tone, joint mobility, proprioception and pain is of considerable interest to practitioners using manipulation. It has long been hypothesized that dysfunctional articulations may generate altered patterns of afferent input. This article reviews the relevant studies that have investigated the impact of articular input on efferent activity under normal conditions and under conditions of altered joint function. The findings suggest that sensory input does have a substantial effect on efferent function and sensation. Furthermore, the studies indicate that the pattern of articular input may be significantly modified by joint inflammation, trauma and effusion and result in changes of muscle tone, joint mobility, proprioception and pain.