Describe flexion of the ethmoid
Perpendicular plate is rotated by the sphenoid about its transverse axis — this swings the crista galli superiorly and posteriorly
There may be accompanying external rotation — lateral masses expand inferiorly (using attachments to cribriform plate as a hinge) d/t pull of external rotation of the maxillae
Describe extension of the ethmoid
Perpendicular plate is rotated by the sphenoid about its transverse axis — this swings the crista galli inferiorly and anteriorly
May be accompanied by internal rotation d/t internal rotation of maxillae with SBS extension
Clinical considerations with ethmoid SD
Sinusitis (ethmoid bone has pumping action on ethmoid sinus)
Septal deviation (ethmoid spine allows some lateral deviation)
Headache (d/t lymphatic drainage through cribriform plate; increased dural tension or vascular effects may lead to tension HA or migraine symptomatology)
Axes associated with SBS vertical strain
2 transverse axes
With superior vertical strain, bones rotate anteriorly around involved axis; with inferior vertical strain, bones rotate posteriorly around involved axis
With a superior vertical strain, the sphenoid is considered _____ while the occiput is considered _____
Flexed; extended
The sphenoid is flexed with rotation around its transverse axis and basisphenoid superior; bilateral anterior quadrants are in external rotation
The occiput is extended with rotation around its tranverse axis; bilateral posterior quadrants are in internal rotation
[opposite is true with inferior vertical strain]
Axes associated with SBS torsion
Sphenoid and occiput rotate in opposite directions around an AP (sagittal) axis
The side with the higher greater wing = anterior quadrant is in relative external rotation
The side with the lower greater wing =anterior quadrant is in relative internal rotation
[Dr. Danto note — “For torsions, think of the sphenoid on the high-wing side as being in extension and the Occiput on that side being in flexion…and vice versa on the opposite side. However, due to the wonderful mechanics of the human body, the Occiput drives all of the paired bones into External Rotation when it is in flexion. So that is why all the facial features essentially match those found in ER despite the sphenoid being in extension (usually matched with IR)”]
Axes associated with SBS lateral strain
2 vertical axes (superior/inferior) — go through foramen magnum and body of the sphenoid
Which of the cranial strain patterns is referred to as a “parallelogram head”?
SBS lateral strain
Axes associated with sidebending rotation dysfunction
1 sagittal (AP) axis from opisthion to nasion = rotation; sphenoid and occiput spin in same direction
2 vertical axes: FM and body of sphenoid = sidebending; sphenoid and occiput spin in opposite directions
Note: the side of the lower greater wing and occiput is in relative flexion; high side is in relative extension [named side feels fuller]
Vault contact palpation technique to test for SBS compression
Lift lateral angles of frontal bone anteriorly with thumbs while stabilizing the lateral angles of the occiput posteriorly with the hands — focus attention on SBS
Findings in SBS flexion SD in terms of restricted motion, head diameter, forehead, eyes, paired bones, ears
Restricted motion = extension
Head diameter increased in transverse dimension
Forehead wide and sloping
Eyes prominent
Paired bones externally rotated
Ears protruding
Findings in SBS extension SD in terms of restricted motion, head diameter, forehead, eyes, paired bones, ears
Restricted motion = flexion
Head diameter increased in longitudinal dimension
Forehead vertical
Eyes receded
Paired bones IR
Ears close to head
Findings in SBS torsion in terms of the following on the side of the HIGH sphenoid wing:
Frontal lateral angle Orbit Frontozygomatic angle Eyeball Zygomatic orbital rim Symphysis menti Mastoid tip Ear
Frontal lateral angle anterior Orbit wide Frontozygomatic angle increased Eyeball protruded Zygomatic orbital rim everted and ER Symphysis menti toward high side Mastoid tip posteromedial Ear protruding
Findings in SBS torsion in terms of the following on the side of the LOW sphenoid wing:
Frontal lateral angle Orbit Frontozygomatic angle Eyeball Zygomatic orbital rim Symphysis menti Mastoid tip Ear
Frontal lateral angle posterior Orbit narrow Frontozygomatic angle lessened Eyeball retruded Zygomatic orbital rim inverted and IR Symphysis menti away from low side Mastoid tip anterolateral Ear close to head
Findings in SBS sidebending and rotation on side of concavity:
Frontal lateral angle Orbit Frontozygomatic angle Eyeball Zygomatic orbital rim Symphysis menti Mastoid tip Ear
Frontal lateral angle posterior Orbit narrow Frontozygomatic angle lessened Eyeball retruded Zygomatic orbital rim prominent Symphysis menti towards concavity Mastoid tip posteromedial Ear protruding
[note side of concavity is in extension/IR]
Findings in SBS sidebending and rotation on side of convexity:
Frontal lateral angle Orbit Frontozygomatic angle Eyeball Zygomatic orbital rim Symphysis menti Mastoid tip Ear
Frontal lateral angle anterior Orbit wide Frontozygomatic angle increased Eyeball protruded Zygomatic orbital rim flat Symphysis menti away from convexity Mastoid tip anterolateral Ear close to head
[note side of convexity is in flexion/ER]
