Facilitation refers to the maintenance of neurons in a state of partial excitation. It can be caused by a variety of reflexes connecting the spinal cord, muscles, skin, and viscera. The most common ones are somato-somatic, somatovisceral, viscerocutaneous, viscerosomatic, and viscero-visceral.

These reflexes become pathologic when they cause facilitation that leads to somatic dysfunction. For example, organ impairment can cause facilitation that results in somatic dysfunction of the muscles innervated by the same spinal cord segments as that organ. By recognizing and treating facilitated segments, osteopathic physicians can correct these reflexes.

A viscerosomatic reflex is defined as “localized visceral stimuli producing patterns of reflex response in segmentally related somatic structures” (Giusti). In other words, a viscerosomatic reflex is an effect on the somatic system (bones, muscles, joints) resulting from a visceral pathologic state or disease.

Viscerosomatic reflexes may also manifest as an imbalance of the sympathetic or parasympathetic nervous systems. Somatic dysfunctions that manifest via the sympathetic nervous system may be found at the T1–L2 levels. Somatic dysfunctions that manifest via the parasympathetic nervous system may be located at the upper cervicals (OA joint, C1, C2) and S2–S4 (pelvic splanchnic nerves).