Body Mechanics
Picture a balloon in the shape of a tadpole. This fluid filled balloon houses and protects the CNS. The fluid is called Cerebrospinal fluid (CSF) , and is produced in a rhythmical cycle by the brain roughly every 3 to 4 seconds, followed by another 3 to 4 seconds of reabsorption back into the blood supply.
The head of the balloon – or Dura – moulds to the inside of the skull, and very strongly to the base of the skull, or Occiput, where the spinal cord exits.
The body of the tadpole shaped balloon travels down through the neck and back and mechanically connects to the tailbone, or Sacrum.
This is where the mechanics come in, and provide us with an invaluable diagnostic tool, enabling us to work with conditions that would never show on scans or x rays.
As the CSF is produced, the balloon expands. As it does so, because it is moulded to the inside of the skull plates, they all widen and move apart slightly.
When the correct volume of CSF is achieved, the body senses that and slows production down. Reabsorption takes place, and when the CSF volume drops low again, it kick starts another production cycle and so on.
Expanding Cranium
This is the interesting bit! All of the skull plates mould together like a tight-fitting jigsaw. But the sutures, where they join together, are not fused – they allow for a little movement to facilitate the expansion and contraction of the plates as the balloon on the inside does the same.
We can use this diagnostically, as with very light touch you can assess if a plate has been traumatised, jammed, or is restricted in its range of motion by other factors like tight connective muscles, distortions of the Dura or scar tissue from surgery.
The base of the skull, or occiput, rocks down towards the feet during production of CSF, and back up towards the head in reabsorption phase. Because the body of the tadpole is moulded to this bone, it gets dragged up and down through the neck and the back as the occiput moves. The tailbone then moves because the Dura is moulded to it, so we end up with a swing boat effect where both tail and base of the skull rock forwards and backwards together in conjunction with the production and reabsorption of CSF.
With very light touch through a fully clothed body, we are able to determine if these basic fundamental mechanics of the system are working ok, or compromised in some way. What might cause a problem and impact on the CNS? Life!!!