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A Tough Reclusive Mother - Palpating the Cranial Dura Mater (Part 1)

Note: This is a two-part ‘how-to’ article.  Part 1 focuses on anatomy and mechanics; Part 2 gives some methods of application.

Imagine placing your hands on the above head, and engaging the outer tissues in such a way as to transmit force to the membrane shown in yellow.  Imagine that doing so with skill and intention can lead to positive physiologic change.  Those are the two basic premises of dural contact in bodywork.

We’ll skip for now a discussion of why you might want to do this, and what physiologic changes it may induce.  We’ll also duck questions on craniosacral work and cranial osteopathy, because both are cluttered with concepts unhelpful for a grounded discussion. We will try to make only reasonable assumptions.

The first thing we need for effective dural palpation is to imagine the body from the Dura’s perspective.

The Inmost Skin

The Dura Mater is a fascial membrane that encloses our central nervous system, and continues as nerve sheaths to every corner of the body.  It hangs suspended, tugged in all directions, inside our cranium and spinal canal.

We could call it the deepest fascial tissue, since it lies housed within the embryonic midline.  All other fascia migrates outward as the embryo grows, but the Dura (once you can call it that) stays put.  Its fidelity to midline wins the Dura a great deal of protection — a strong bony sheath and a thick muscular envelope.  The only problem, because of its connectedness and centrality, is that it constantly must adjust to the movements of long limbs, floppy necks, and twisting spines.

Does it care?  Has the Dura any need of mechanical health?  Is this ‘tough mother’ really so uptight?   Like all ivory tower-dwellers, the Dura can be prone to strong reactions.  It’s not always inflamed or hypersensitive, but when it is, whoo boy.  The body takes great pains to avoid its ire.  (For background on this, ask the Australian PTs.  In fact, just ask them about everything.)

Directions for preparing your Dura: 1) Dessicate, 2) Slice open carefully, 3) Scoop out brain (save for later), 4) Garnish with numbers.

One thing shared by every nervous system is the remarkable degree to which other tissues protect it.  Bones and fasciae turn direct forces into harmless obliquities.  Layered fluid chambers convert loud vibrations to gentle murmurs.  Blood vessels are grasped and filtered by glial cells.  And muscles constantly limit their own length based on a neuro-protective policy.

But don’t take my word for it:  Try sinking into a gentle hamstring stretch.  Keep a neutral back and a long spine, with your eyes pointing down.  Stop when you encounter the first resistance.  Now, extend your head to look forward.  You just fed dural slack into your spinal column — does the hamstring allow a deeper bend?

This is the world as seen by the Dura.  Cradled, bathed, actively protected, it constantly shifts within the body’s lumbering expanse, tasked with protecting the most fragile of all organs.  One could understand why it might get starved for attention.

Dura as a Water Balloon

No fascial tissue can really be understood without fluid pressure in the picture. This is the case with Dura, against whose interior the cerebrospinal fluid (CSF) pushes outward at 2-3 kiloPascal.  (Note: 1 kPa roughly equals 1 standard water balloon.)

Why would the body maintain such a pressurization?  Because the stiff competition between CSF and Dura accomplishes a fantastic evolutionary feat:  Our delicate sopping hulk of a brain, which normally weighs 1300 grams is reduced to 50.  Fluid and fascia also create a pressure-tension buffer, which neutralizes vibrations and impact force.

When you think about it, a water balloon displays a form of tensegrity.  Its integrity based on the dynamic balance between opposed forces of tension and compression.  In a classic tensegrity model, dowels represent compression members and bungee cords represent tension members.  Squash this dowel-and-bungee model, and it springs back into shape.  Distort one corner of it, and the whole structure adjusts to find a new balance.  Bodyworkers (like the inimitable Tom Myers) have long used these models to describe the mechanical relationship of bones to the fascial matrix.

Fetal bones spread like ice sheets along the surface of the dural balloon.

But the same behavior can also be seen in fascial fluid chambers.  Instead of dowels, they have compartmental fluid pressure.  Instead of bungee cords, it’s membranes under tension — call it ‘Planar’ or ‘Fluid’ tensegrity.  Everything from single cells to muscles to dural balloons display these same properties — elastic memory and systemic re-balancing.

Look back at that yellow line at the top of the page.  Imagine resting your finger pads gently on the outer surface, and directing a light inward pressure through the bone.  The bone resists you, of course — but is it only bone?  Or can you feel the dural balloon on the bone’s interior?

You might be thinking, “Waaaaaaait a minute.  How does one feel through bon