The Central Nervous System

There’s a phenomenon you may notice when you’ve been working with peripheral nerves for a while. Often you may find a sidedness to neural inflammation. The tibial n. (on the medial leg), will be inflamed on, say, the left side, and the sural n. (lateral leg) will be hot on the right. Then halfway through the session you may recheck and find the pattern reversed. Hmmm, you might say to yourself, what’s going on here?

If you were also to check pelvic rotations, you might notice that the tibial n inflammation occurred on the side of the posterior ilium and sural n on the anterior side. And you may find the pelvis has shifted its side of anteriority at the same time as the inflammation in the legs switches. There’s a reason for all this, and it has to do with with the organization of the central nervous system (CNS from here on).

Cortical Dominance

Like the rest of the body the CNS is often subject to imbalance. Here imbalance shows up as a difference in firing rates of the cortical hemispheres. Why this occurs I’ll explain later. What it means for the structure and peripheral nervous system is more important for the work we are doing.

I often use a simple demo to illustrate the principles of the CNS. With a model lying on the table, I’ll determine the side of pelvic anteriority, which is easily replicable by members of the group. Let’s say there is a right anterior ilium and the vertebral pattern which accompanies it, including a noticeable contraction in the left lumbar musculature. I’ll use a digital metronome to introduce a sound into his right ear for perhaps 15 seconds. When we re-check the entire structural pattern has shifted - not only the pelvis, but the vertebrae and lumbar curve - even the head tilt changes. Surprisingly perhaps, patterns of neural inflammation also change.

For most people who work with bodies - particularly those who are concerned with balance, the demo is challenging to long-held beliefs. How can a sound in one ear change patterns that all my excellent work has not resolved? It doesn’t have to be a sound. It could been a beam of light directed from the right field of gaze toward the left, or even a flavorful candy held in the right cheek. It is, more importantly, a neural input from one receptor field that travels through the sensory nerves to the cerebral cortex on the opposite side. It changes the firing rate of that side of the brain.

Why is firing rate of the brain important to how the body is organized? The simple answer is: the brain is responsible for initiating movement and for controlling spindle cell activity (and thus muscle tension), among its numerous other tasks. What is important for us is that we can easily evaluate these functions and make predictions about how the body should behave. We can determine, for instance, that if a client has a right head tilt, chances are that is his dominant side. Hold the questions for a moment, please.

There might, of course, be other forces at work. He might be tilting his head to correct for an extra ocular muscle that is weak and won’t move his eye into position. and we can test that, if we want to, by further variables. But under normal circumstances we can predict that his right head tilt will be associated with a right anterior pelvis assuming the rest of his body is congruent.

Why are we taking this route?

In prevous classes, the concepts surrounding the CNS have been a bit overwhelming for students, given the relatively short amount of time they deserve in the overall discussion. CNS behavior is a relatively small part of the discussion of working with peripheral nerves, but it is, I feel, a useful one for understanding the shifting phenomena you will see when you get into working with the neurology of posture.
But the power of this way of investigating is not for the “congruent” cases where everything goes as predicted, but those cases where the upper body demonstrates one pattern, while the pelvis and legs apparently have the opposite one - an “incongruent” case.

The Underlying principles:

These are some of the principles which govern the behavior of the CNS. For people new to neurology, they are sometimes difficult to grasp.

1) Afferentation: The nervous system is driven by afferentation. This means that the activity of the entire system relies entirely on the firing of various sensory receptors and, in particular, by gravity-driven sensory receptors (important for Structural Integrators) for its survival.

Neurons require the stimulation by pre-synaptic neurons to survive. That means that any nerve cell in your body will undergo deleterious changes and ultimately die if the nerves which terminate on it stop firing. This is built into the design. When the cell is fired upon, signals to the nucleus cause it to build proteins which help repair the cell, maintain the gell-like internal milieu, and also maintain the membrane potential which is required to generate action potentials (the signals that nerves use to communicate with one another).

The beginnings of the chain of firing are the receptor cells (the cells which populate the eyes, ears, and taste buds, for instance) which transduce light, sound, etc. or joint movement into action potentials. What this means is that the entire nervous system would fail if the receptor cells of the body stopped firing. The rate of receptor cell firing, called Frequency of Firing (FOF), is responsible for the overall viability of the CNS.

2) Hemispheric Dominance: Because, it seems, our bodies are inherently imbalanced, imbalance shows up in the CNS. Generally, the imbalance is caused by a difference in afferentation (see above). Since gravity-dependent receptors — spindle cells and joint mechano-receptors — provide the large bulk of sensory input to the brain, injury or impairment of joint motion limits the afferent input to the brain hemisphere on the side opposite the impairment. To explain further, all sensory neurons in the body fire to the contralateral hemisphere of the brain. So lack of sensory input from the right side, causes the opposite cortex, the left side, to slow its firing rate. This makes the right cortex, in this example, the “dominant cortex”.

3) Inhibition of Inhibition: The cerebral cortex is responsible, among many other duties, for the “inhibition of inhibition” of motor commands. This concept warrants a little teasing out, as it seems to be counter-intuitive for many. We’ll use a phylogenetic example.

When the hydra - a simple multicellular animal a few evolutionary steps above a sponge - senses molecules that indicate food, his tentacles contract around the morsel and he engulfs it in one swift movement with very little subtlety. If it turns out not to be what he wanted, he has no means of stopping the action, though he can disgorge it once it is inside his gastric cavity.

As we wander up the evolutionary chain, the ability to inhibit activity develops. The organism is able to act, and it is also able to curtail the action. It’s still rather crude but probably keeps the organism out of a certain amount of trouble.

It’s not until the development of the cortex that we have true graded motion. An analogy is trying to inch your car forward. You have your foot on the gas and the brake at the same time. When you want to move, you don’t tromp on the gas. You ease your foot off the brake. The car eases forward. So you’ve effectively inhibited the effect of the braking, which was an inhibition of the forward motion.

Without inhibition of inhibition, playing piano would have no nuance, and eating with a fork would be a life-threatening adventure. Here’s a simplified version of how it works?

When you go to move your right leg, the left cortex initiates the motor signal (contra-laterally) down the neuraxis to the ventral horn cell in the spinal cord of the lumbar area. This signal excites the motor neuron to your right leg. It simultaneously excites an inhibitory cell which circles back and partially cancels the action it just initiated. It takes the ipsilateral brain (the right brain in this example) to inhibit the inhibitory cell so the action can take place.

This is even more important on the non-dominant (left) side. Here the ipsi-lateral cortex (the left brain) is unable to maintain the inhibition of the inhibition of the faster-firing right (contralateral) side, and the muscles of the left leg are weaker. The weakness of the non-dominant leg is relative to the difference of firing rates of the two hemispheres.

4) Specific Inhibition: In a completely separate activity from inhibiiton of inhibiition, the cerebral cortex also selectively inhibits the anterior muscles above T-6 and posterior muscles below T-6 — upper body flexors and lower body extensors. The functional reason for this is probably to keep muscle groups that get more use from overpowering their antagonists. This principle helps explain another non-dominant phenomenon - that the left leg extensors are more contracted than their right leg counterparts - because the left brain’s inhibition is diminished.

5) Cross Cord Reflexes: When a motor neuron is fired to a muscle in the right hip flexor, whether reflexively (in response to a stretch reflex) or suprasegmentally (from the brainstem or cortex) at least 7 other neurons pools are affected. The right hip extensors are inhibited. (You may know this phenomenon as the balance between agonist and antagonist muscles.) On the left side the hip flexors are inhibited, and extensors are excited. And the reverse pattern takes place in the upper girdle. So in our model of right-sided hip flexor contraction, the right neck extensors will contract as will the left neck flexors.

6) Oxidative Capacity: The oxidative capacity of the body and hence the firing rate of the cerebral cortex diminishes by about 1% per year after age 20. This doesn’t directly relate to our current discussion but has an interesting correlate with #3. When people reach their 50’s they’ve lost 30% of their oxidative capacity and thus 30% of the inhibitory power of the brain. This is about the age when you start to see shoulder problems showing up because the pectorals are no longer well inhibited and the back muscles are losing ground. By 70’s the extensors of the legs have lost their cortical inhibition and have contracted so much you start to get the typical older person’s posture of shoulders rounded and knees bent.

Applying the Principles

If this is the first time you’ve encountered this information, its a lot to digest, so we’ll take this piecemeal. Of general note, about 80% of the population is right brain dominant, so we will use that model in our discussion. With a dominant right cortex we can expect the following pattern:

a) Right ilium goes anterior. This is predicted from principles 3 & 4 above. The dominant right cortex causes the anterior hip flexors - especially the iliacus - to control the action while the right hip extensors are inhibited (4).

b) Left ilium goes posterior. Specific inhibition (4) dictates that the leg extensors are inhibited, but the weakness of the left cortex (remember right side is dominant) causes the ipsilateral inhibition of the left extensors to be less effective than the right. Since lack of inhibition equals contraction, the left ilium is pulled posterior. This pattern is also predicted by the cross-cord reflex (5).

c) Sacrum and L5 follow the dominant ilium. In the normal pattern they do. Where use of this model is most powerful is in sorting out the aberrations - the incongruent patterns.

d) Left Lumbar musculature contracts. This follows the same explanation as (b), because lumbar muscles are part of the same group of extensors as the hamstrings. You will see this pattern well-represented in scoliosis cases. The lowest curve will generally be on the subdominant side

e) Right head tilt. Posterior upper girdle muscles contract follow cross-cord reflex pattern.

f) Left neck angulation. The left anterior neck muscles again follow cross-cord. It is sometimes easy to mistake neck angulation for head tilt or vice versa.

There you have it. There are other specific muscle contractions which are predicted and pretty much follow the pattern. I use an assessment technique which allows me to rapidly determine the pattern or deviation from it. It is the deviations that are the most interesting, and they typically show up in clients with chronic pain patterns.

In the hypothetical problem at the beginning of the paper, I used the metronome to flood the non-dominant hemisphere with stimulation, thereby reversing the side of dominance. In that example the results are temporary, lasting a minute or so, but you get to see how quickly the entire system responds. To the degree that the pattern follows the one above, the whole pattern will shift when the dominant cortex shifts. As I said, when there are aberrant patterns is when it gets interesting.

The Peripheral Nervous System

The local - the grass roots - perspective involves approaching the nervous system as palpable tissue. And here we are talking about the peripheral nervous system (PNS) because the CNS is encased in bone. This is about direct contact - through the skin, of course - with nerve tissue and its connective tissue sheath. It takes a while to get the feel — partly because nervous tissue has so many different feels, from tight tiny wires to boggy tubes of jello, and larger nerves are often indistinguishable from tendons.

One of the first things you discover when you begin to work directly with nerve tissue is that chronic pain seems to resolve when the nerve itself, not the myofascial tissue, quiets down. You might begin to get the suspicion that chronic myofascial pain syndromes don’t exist, that most chronic pain may have neurogenic origins. You would have experimental support for such a view, for instance at the following website: http://websites.golden-orb.com/pain-education/100137.php.

I understand that many practitioners have an aversion to working on symptoms, preferring to focus on structural balance issues. However, I’ve found, particularly in chronic pain cases, that the symptom, or the avoidance of it, often creates the postural distortion. Secondly, chronic muscle contraction, when there is neurogenic bombardment of the muscle, is difficult to resolve. In other words, if the nerve is firing because of irritation to the nerve itself, working on the end organ is often pointless.

Two conditions which are typically considered to have myofascial origins are rotator cuff syndrome and plantar fasciatis. In the cases I’ve seen, both resolve when the innervating pathways are quieted. Another learning, at least for me as I became comfortable palpating for nerve fibers, is the ubiquity of the stuff. Particularly when they are irritated and thus more sharply defined, there’s not an area of skin that isn’t rippling with nerve fibers. What that means for those who like those long elbow strokes may at least give them pause. This is tissue we’re affecting all the time, but doing so unconsciously.

Jean-Pierre Barral, D.O. has developed a technique for working with peripheral and cranial nerves that follows the tradition he established with his visceral work. His work is organized around the following aims:

To maintain the mobility and glide of nerves

To reduce the pressure on the nerve

To affect the proprioceptive system

To affect the electromagnetic field

To affect the emotional system

While his work is fascinating and very comprehensive, his attention to cranial nerves and their effect on brain function, which is his primary interest, will have to wait for another day for me. In my practice my use of his work has been somewhat less inclusive. I have been concerned with the ways that peripheral nerves affect local conditions relating to joint freedom and pain and how that limits and determines overall organization of structure.

Anatomy of a Bundle

The anatomy of the nerve fiber is complex. The neuron, the individual nerve cell, has its own internal complexity which we won’t review here. Each neuronal axon has its own fascial sheath, the endoneurium, as does each bundle of axons, the perineurium, and the entire peripheral nerve, the epineurium. The bundle has its own vascular supply, the vasa neurvorum, and nerve supply, the nervi nervorum. It is this complex of structures that give nerves their local importance in the overall structural picture. I have found mention in a couple of articles of contractile properties of perineural cells, but not much detail.

Neurogenic pain

There are several ways nerves can be compromised and several sequellae of each.

1) When peripheral nerves are damaged, stretched, compressed or ablated, sensitization occurs because of spontaneous activity of the neurons themselves. If the fibers are nociceptors (pain receptors), this results in increased pain at the site of distribution. If they are motor nerves, increased activation causes muscular contraction.

2) The nervi nervorum is responsive to stretch of the nerve bundle causing neuropathic pain when over-stretched.

3) The vasa nervorum is also susceptible to stretch and compression leading to hypoxia of local tissue.

There is an additional phenomenon that contributes to the local and global scene that is known as “cross-talk”. Crosstalk occurs when excitability of activated fibers jump the track, so to speak, and activate fibers in close proximity. This can cause referred pain syndromes, but more importantly for our purposes, it can lead to the activation of motor neurons when pain driven sensory neurons are activated nearby. This leads to the familiar pattern of muscle spasm around a painful joint.

As an example of the power of this cross-talk phenomenon, I recently had a client whose jaw was so painful and spasmed she could barely open her teeth more than 1/4 inch. The masseter was too sensitive to even touch. Halfway into the session I had not begun to reduce her difficulty. In a flit of insight I recalled that the trigeminal nerve which innervates the jaw muscle has several sensory which innervate the face through foramena in the skull. These endings were sensitive but not overly painful. As I was able to reduce the sensitivity of the nerve twigs, the jaw began to relax and finally the intense pain in jaw muscles and teeth was able to subside. The diminished tone in the sensory branch allowed the entire complex to quiet.

Using Barral’s technique, which could be described as rhythmically compressing the fiber to restore its normal visco-elasticity and stretch, leads to several unexpected results along the line of the previous paragraph. Working on a nerve that exits the spine at a particular level can have effects of nerves that either exit or enter at that level. Barral uses an example of working on the liver, which is innervated by the phrenic nerve that exits at C5, to release the shoulder which is also innervated from C5.

The phenomenon that surprised me the most was how much chronic pain, which is experienced as diffuse and covering a large area, is actually very precisely located at the nerve fiber itself. The pain is either caused by excitation of the nerve somewhere along its pathway or, at very least, is extinguished by working along the pathway.

Science and medicine separatethe object of study into systems. Of all the body’s systems, it is least possible to separate the nervous and musculo-skeletal system. They develop together and perform in synchrony. Somatic workers have ignored the nervous system — perhaps because of its daunting complexity. But ignoring it does not reduce its influence. It is ultimately “neuro-myo-fascial manipulation”, whether we choose to recognize the “neuro” or not.