Referred pain from the viscera
Another facet of chronic pain is pain that can have its origins elsewhere, specifically in the viscera. This can cause local pain, or causing adaptations with a change in posture or function
All the viscera is attached to something. That something could be the respiratory diaphragm, the back, or the pelvis. The viscera also like to 'move' and if they cannot move the way they wish, they will have voice - they give us symptoms
An example of this is the heart. It has it embryological origins in the neck and upper chest and takes a nerve supply with it (the phrenic nerve) as it descends to its final place in the chest. The phrenic nerve supply is really a two way street and sensory information can pass back up into the spinal cord. Here it can ‘overflow’ into the somatic system, then being felt elsewhere in the body.
The pericardium and its support ligaments, connect to the cervical and thoracic spine and sternum. The pericardium is suspended from behind by a continuous skin of ligament from the bodies of all vertebrae C4 - T4, and also supported at the front to the back surface of the sternum by two ligamentous local thickenings at the level of the third and fifth ribs.
These pericardial support ligament strains produced by whiplash or other impact injuries are frequently expressed as low cervical and upper thoracic stiffness and pain. It is this reason that the heart can refer symptoms to the left shoulder, left arm and the angle of the jaw on the left with situations like myocardial infarction, as well as the ‘usual’ one of crushing, retrosternal pain.
Now, this is an extreme example. Frequently there can be ‘low grade’ referral patterns with the person experiencing stiffness in the chest, shoulder and neck. These may be present for years before the person seeks attention for their discomfort.
These can be expressions of mobility, motility or embryological rotations of the viscera along the course of their lifetime. So it may be that things cannot ‘move as they wish’, and if they cannot, will have voice; that voice being the soma – muscles and joints.
The pictures also show the regions of the back that have relations with it from its attachments from the gut . The shaded regions show regions covered with peritoneum (hence can be freely movable) and bare areas (that show where tissues have a direct attachment to the back).
Structures that have a direct relationship with the back can refer pain directly to those areas. Note here the ascending and descending colon have a direct connection with the back and the lines drawn across the back by the mesentary of the other regions of the gut. The attachments can cause referred pain through to the back.
In addition to these, there are attachments to the respiratory diaphragm (these can give referred symptoms back up to the shoulder and neck (through the phrenic nerve), and to the pelvis, giving pain and stiffness in the hips and lower limbs.
The above picture shows the same attachments from the side
These all can give rise to pain pictures elsewhere in the body, as shown by the picture below