A spinal nerve with its anterior and posterior roots.

• A spinal nerve with its anterior and posterior roots.
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• Nerve compression hypothesis: suggests that when the vertebrae are out of alignment, the nerve roots and/or spinal cord can become pinched or irritated. While the most commonly referenced hypothesis, and easiest for a patient to understand, it may be the least likely to occur.
• Proprioceptive insult hypothesis: focuses on articular alterations causing hyperactivity of the sensory nerve fibers.
• Somatosympathetic reflex hypothesis: all the visceral organ functions can be reflexly affected by cutaneous or muscular stimulation.
• Somatosomatic reflex hypothesis: afferent impulses from one part of the body can result in reflex activity in other parts of the body.
• Viscerosomatic reflex hypothesis: visceral afferent fibers cause reflex somatic problems.
• Somatopsychic hypothesis: the effects of a subluxation on the ascending paths of the reticular activating system.
• Neurodystrophic hypothesis: focuses on lowered tissue resistance that results from abnormal innervation.
• Dentate ligament-cord distortion hypothesis: upper cervical misalignments can cause the dentate ligaments to put a stress on the spinal cord.
• Psychogenic hypothesis: emotions, such as stress, causing contraction in skeletal muscles.

The vertebral subluxation has been described as a syndrome with signs and symptoms which include: altered alignment; aberrant motion; palpable soft tissue changes; localized/referred pain; muscle contraction or imbalance; altered physiological function; reversible with adjustment/manipulation; focal tenderness.