Motion of the Sphenobasilar Synchondrosis (SBS)

00:01 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.

00:12 The motion patterns are described in reference to the SBS.

00:16 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.

00:25 The cranium's designed so that when it absorbs any sort of forces, those forces are directed to the center where it's absorbed.

00:33 Motion occurs at the cranial base about 2 transverse axes.

00:38 And so the midline bones, the sphenoid and the occiput move in a gear-like fashion about 2 transverse axes.

00:45 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.

00:59 So when you have motion at the SBS, different forces could produce certain strains at the base.

01:06 The SBS could accomodate different forces but sometimes you may have something that moves out of pattern.

01:13 The normal motion pattern is usually flexion and extension.

01:17 The motion of the sphenoid and occiput about two transverse axes, these forces might cause asymmetry.

01:26 Certain forces such as fascial pulls from below the cranium could cause asymmetry.

01:31 Local cranial somatic dysfunctions, either trauma or due to different forces could also cause a alteration of what's going on at the base.

01:40 Spinal/ pelvic assymetries could also lead to cranial asymmetries.

01:46 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.

01:54 And what we do is we have different positions and contacts to help try to diagnose that cranial base.

02:01 Pretty much all these different hand contacts are on the vault.

02:05 This is what we could contact in terms of trying to look at what's going on at the base.

02:11 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.

02:18 And so the floor, the inside of the house is pretty much floor - the living room.

02:27 and so your hands are looking from outside through the windows.

02:32 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.

02:40 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.

02:52 So one of the most basic contacts is called the vault hold.

02:56 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.

03:08 Your hand positioning is really important here to gather as much information as you can.

03:13 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.

03:21 You don't wanna squeeze too hard, you don't wanna put too much pressure 'cause you don't want to cause patient's discomfort.

03:29 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, overlapping pterion.

03:38 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.

03:46 Our ring finger is gonna be over the posterior aspect of the ear and along the squamous portion of the temporal bone.

03:53 And our pinky finger is gonna kinda reach back and try to get a sense of the occiput.

03:58 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.

04:05 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.

04:14 There are some additional hand holds that could improve your ability to take a look at what's going on with the cranium.

04:20 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.

04:32 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.

04:40 So here, what we're doing is we're contacting the vault using two different hand holds.

04:45 Here, we're gonna place one hand horizontally across the inion.

04:50 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.

05:16 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.

05:30 We could also diagnose cranial somatic dysfunctions using the posterior occipital contact or also called the Becker hold.

05:40 And so, this hold gives you a better view of what's going on the posterior cranial fossa.

05:45 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.

05:55 Your fingers are gonna kinda stretch down and relax along the cervical spine and the neck.

06:00 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.