Motion of the sphenobasilar synchondrosis
So the sphenobasilar synchondrosis is the
attachment of the sphenoid to the occiput
where they meet at the center of the skull.
The motion patterns are
described in reference to the SBS.
So the SBS is at the center
of the cranial base and so
it is a nice reference point to
what is going on around the skull.
The cranium's designed so that when
it absorbs any sort of forces,
those forces are directed to the
center where it's absorbed.
Motion occurs at the cranial base
about 2 transverse axes.
And so the midline bones, the sphenoid and the occiput
move in a gear-like fashion about 2 transverse axes.
The motion is called flexion and
extension or in other terminology,
commonly used is inhalation for the flexion
phase and exhalation for the extension phase.
So when you have motion at the SBS, different
forces could produce certain strains at the base.
The SBS could accomodate different forces but sometimes
you may have something that moves out of pattern.
The normal motion pattern is
usually flexion and extension.
The motion of the sphenoid and occiput about two
these forces might cause asymmetry.
Certain forces such as fascial pulls from
below the cranium could cause asymmetry.
Local cranial somatic dysfunctions,
either trauma or due to different forces
could also cause a alteration
of what's going on at the base.
Spinal/ pelvic assymetries could
also lead to cranial asymmetries.
So when we are looking at
the motion of the SBS,
in order to diagnose what's going on at the
cranial base, we need to have a starting point.
And what we do is we have different positions and
contacts to help try to diagnose that cranial base.
Pretty much all these different
hand contacts are on the vault.
This is what we could contact in terms of
trying to look at what's going on at the base.
So the analogy I like to have is like if you're trying
to look at the cranium, like you're looking at a house.
And so the floor, the inside of the house is
pretty much floor - the living room.
and so your hands are looking
from outside through the windows.
And so when you're contacting
the outside of the house,
you're getting a sense of what's going on at
the base or the foundation of this house.
So from this different contacts,
your goal is to get an idea
what's going on, what is moving,
what's not moving
and if there's a different sort of strain, twist
or turn at the base.
So one of the most basic contacts
is called the vault hold.
Here, what we're doing is we're using our
hands, place a gentle contact on the vault
and again, trying to perceive what has been
accommodated based on what's moving at the base.
Your hand positioning is really important here
to gather as much information as you can.
You want to make sure that your hand positioning
is correct and you wanna have a gentle contact,
almost like a plastic contact
against the bones of the cranium.
You don't wanna squeeze too hard,
you don't wanna put too much pressure
'cause you don't want to cause
So when we're looking at the actual vault hold,
we're going to place our pointer fingers
at the greater wing of the sphenoid,
We're going to have our middle
finger in front of the ear
covering the squamous portion of the temporal
bone and slightly over the parietal bone.
Our ring finger is gonna be over
the posterior aspect of the ear
and along the squamous portion
of the temporal bone.
And our pinky finger is gonna kinda reach
back and try to get a sense of the occiput.
You're gonna do the same on both hands
and then your thumbs are gonna either
cross or gently touch but you're not
gonna push down on the head with it.
And so what this contact - this vault hold
contact, what you're getting sense of is
really almost like what is going on with
the head through the cranial bones.
There are some additional hand holds
that could improve your ability
to take a look at what's
going on with the cranium.
If you're going to try to get a sense
of what's going on at the base,
the more positions that you have,
the more views that you have,
could potentially help you with what
you're trying to assess and diagnose.
And so, a frontal occipital hold is another
hand contact where you're going to have
more of a anterior-posterior
observation of the cranium.
So here, what we're doing is we're contacting
the vault using two different hand holds.
Here, we're gonna place one hand
horizontally across the inion.
So this kinda is a little bit better
if you sit caddy corner at the table
so that your wrist is not too twisted, and so
I'm gonna place one hand horizontally across
the occiput along the nuchal line and the other
hand is gonna come over the frontal bone
with my middle finger kinda
covering the glabella
and my other two fingers kinda covering
over the greater wing if possible.
So with this frontal occipital hold, it's important
to really try to relax your shoulders and your elbows
and to support your elbows if you
can or your forms along the table
as to not to compress as you're
contacting the cranium.
We could also diagnose
cranial somatic dysfunctions
using the posterior occipital contact
or also called the Becker hold.
And so, this hold gives you a better view of
what's going on the posterior cranial fossa.
Your contact is mostly
looking at the occiput,
so you're gonna let your palms rest with the
cranium, the occiput resting on your palms.
Your fingers are gonna kinda stretch down and
relax along the cervical spine and the neck.
And then your thumbs could kinds make it's way up
pointing towards the sphenoid, the greater wing
and then this contact gives your a better
sense of what's going on specifically
more on the posterior aspect of the cranium.