The proposed problems caused by a rotatory subluxation at the atlanto-occipital joint are easily explicable in terms of the applied anatomy of the region. This list should be understood as incomplete, as I am still turning up further complexities as I continue to research this area.
- The curvature of the joint surface means that when the joint is out of place the head will sit unevenly on the neck, with one side tilted higher than the other. The injured person corrects for this by twisting the spine a little to level the head and get it pointing in the same direction as the body. This causes a minor twist (scoliosis) in the spine, and creates an easily detected postural abnormality, involving a twisted and stooped posture (worse when unfit, stressed or unwell).
- The joint subluxation and especially the secondary postural problems interfere with the normal function of most of the main nerves and vessels entering and exiting the base of the skull. Most of the mechanisms suggested below would be considerably less significant if a more upright posture is maintained.
i)The Internal Carotid Artery, Internal Jugular Vein, the Vagus nerve (which mediates the relaxation response to the heart, lungs, intestines, and urogenital tract, provides motor control of the vocal cords and contributes to involuntary emotion related facial expressions), the Accessory Nerve (the muscles between the shoulders) and the Hypoglossal Nerve (tongue and throat muscles) all exit and enter the skull just in front of the atlas. These structures will be stretched across the front of the neck bones whenever the head is forwards and the chin lifted up to look forwards. This will irritate the nerves, and the internal carotid artery and compress the internal jugular vein, delaying drainage of old blood from the brain, and compromising the flow of CSF (cerebrospinal fluid).
3)There is potential for the vertebral arteries and vertebral veins to be compromised interfering with blood flow to the back of the brain.
4) The membranes round the brain will be stretched, maybe pulling on more distant nerves and probably further compromising venous drainage of the brain, and cerebrospinal fluid flow. It is of note that some researchers are commenting on the association between Multiple Sclerosis and chronic venous congestion of the brain.
5) The upper sympathetic nerve ganglion in the neck will be stretched- probably turning on a low level chronic stress reaction. There may well be a physical stress reaction even when not anxious. This is likely in some circumstances to make the sufferer more likely to be unpredictably irritable and anxious. The association of stress reactions with neck rotation or a head forwards posture can be simply confirmed with simple personal biofeedback devices such as the em wave personal stress meter (see http://www.heartmath.com).
6) The spinal cord and brainstem may either be compressed, or be placed under traction in severe cases, or at least irritated in milder cases. This is likely to generate abnormal sensory inputs, and create difficulty with position sensation, balance and “phantom pains” in many parts of the body. Traction on the spinal cord and brain stem will compromise function in these structures. Examples of symptoms caused by this mechanism include pain and spasticity in muscles in the legs and low back, disrupted postural reflexes, compounding the poor posture caused by the subluxation.
7) The atlas subluxation leads to an abnormal posture – which in turn leads to excess load on some neck muscles, especially at the base of the skull. Sensory receptors in these muscles are especially important for giving information about the position of the head in space, contributing to our sense of balance and allowing stable visual tracking of objects while we walk. These inputs also help regulate our alertness and the stimulatory drive to the cerebral cortex. This latter mechanism is a particularly important one.
8) The abnormal loading on the skull caused by the postural abnormalities associated with atlas subluxation will cause shifts in some of the skull joints which, in turn may cause local headaches and impact on more distant structures at the front of the face (ie trigeminal ganglion).
(This area is another one that has been neglected by conventional medicine, which still largely adheres to the idea that these joints are rigid in adults. However many schools of body work are well aware that this is not the case, and directly exploit that knowledge in their treatments).