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Flashcards in OCMM - Paired Bones Deck (42)
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What are the 5 bony articulations of the parietal bone?

Frontal bone
Opposite parietal


The ____ is the old mastoid fontanelle

The _____ is the old sphenoid fontanelle




The ____ bone is the only bone that contacts all 4 fontanelles



Which part of the parietal bone provides attachment point of temporal fascia?

Upper temporal ridge


Which part of the parietal bone is the origin of the temporalis m?

Lower temporal ridge


Which part of of the parietal bone is filled by temporalis m?

Temporalis fossae


Describe the inner surface of the parietal bone

Contains sagittal sulcus (along sagittal suture in which sagittal sinus runs)

Groove of middle meningeal a. (Ant. and post)

There are bevel changes along coronal and lambdoidal articulations

Along lateral part is groove for transverse sinus which carries marginal insertion of tentorium cerebelli


There is a bevel change midway along the sagittal and lambdoidal sutures which creates a hinge for AP axis of motion (coronal plane). What motion occurs in the following parts of the paired bones with SBS flexion:

Inferior borders
Superior borders

Pterion, asterion, and squamous sutures

Sagittal sutures

Inferior borders move laterally

Superior borders move medially and inferiorly

Pterion, asterion, and squamous sutures move laterally

Sagittal suture moves slightly inferiorly

[this is external rotation; cranium widens laterally]


Signs and symptoms of parietal bone SD

Cranial synostosis (premature closure of sutures)

Head pain — pain along a suture

Middle meningeal a. trauma or giant cell arteritis

Head, face, or tooth pain patterns — temporal SD (TrP)

[OSCE says HA, alteration of seizure threshold, localized pain]


Parietal bone SD may manifest as head pain via pain along a suture. What sutures are often involved?

OM and asterion = often involved in tension headaches

Pterion = often involved in temporal headaches



Most common form of synostosis

Sagittal synostosis, accounting for about 50% of all cases

Premature fusion of the sagittal suture restricts the transverse growth of the skull


Form of synostosis most commonly mistaken for posterior positional deformational plagiocephaly

Lambdoid synostosis

When unilateral, results in flattening of the back of the head on affected side as well as compensatory growth of mastoid process on the same side (ipsilateral mastoid bulge) — leads to characteristic ‘tilt’ in cranial base

The ear on the effected side is often deviated back and toward the fused suture


2 parts of temporal bone

Squamous portion — contains zygomatic process (affected in facial injury)

Petrous portion — contains otovestibular organ, eustachian tube exit is between sphenoid and temporal bones, border of foramen lacerum (with sphenoid) = greater superficial petrosal n. and lacrimation via pterygopalatine ganglion, attachment for tentorium, encloses internal carotid a., lateral part of jugular foramen, styloid process


What is unique about the temporal bone of a newborn skull?

Lacks a mastoid process


The mastoid process provides attachment for what muscles?

Longissimus capitis


Internal rotation of the temporals may result in ____ pitched tinnitus


[Internal rotation places pressure on eustachian tubes leading to high pitched tinnitus; External rotation —> low roaring sound or low pitched tinnitus]


Temporal bone motion is driven by the ______ through ____ articulation

Occiput; OM


Describe external rotation of the temporal bone

Squamous portion moves laterally while mastoid process moves medially


Signs and symptoms of temporal bone SD

TMJ pain

Head pain (OM/asterion, pterion, parietosquamous), neck pain d/t SCM or other muscle SD

Dizziness, ear infections, swallowing and chewing (stylohyoid, stylomandibular/TMJ, and styloglossus), tinnitus and eustachian tube dysfunction, bell’s palsy (CN VII)

[OSCE says OM, mastoiditis, tinnitus, hearing loss, dizziness, migraines, Bell’s, neuralgia; dysfunction can be caused by trauma, whiplash, chronic neck tension, dental extraction]


A 23 y/o male presents to the outpatient clinic with right sided head pain and ringing in his right ear 1 week after getting hit with a foul softball on top right side of the head. He was seen in the ER and dx with a grade 1 concussion after x-rays and PE found no neuro defects or fractures. The tinnitus started a day after his injury. MSK findings include:

Right mastoid process medial
Tenderness at point of injury
Right squamous area laterally prominent

What is the most likely temporal SD?

A. External rotation
B. Internal rotation
C. Flexion
D. Extension
E. Superior vertical strain

A. External rotation


Frontal bone articulations



Describe external rotation of the frontal bone

Moves with hingelike motion as if still 2 bones (unfused metopic suture)

During SBS flexion (paired bone external rotation), lateral sides move anterior/lateral and slightly inferior, glabella moves posteriorly


What cranial bone is responsible for moving the frontal bone during external rotation?



Signs and symptoms of frontal bone SD

Head pain d/t pain along suture (coronal in tension headaches, pterion in temporal headaches), head pain d/t diminished PRM and CSF flow d/t increased dural tension at cribriform plate

Sinusitis (allergic or infectious), visual problems, anosmia (frontal influences cribriform plate), frontalis m. TrP/TP

[OSCE says HA, visual or smell disturbance (anosmia d/t ethmoid association), restriction can limit falx and all attachments; can get “wedged” from trauma]


Condition characterised by fusion of both coronal sutures leading to head shape called bracycephaly. Causes restriction of growth of anterior fossa resulting in a shorter and wider than normal skull. Compensatory vertical growth also occurs, called turricephaly

Bicoronal synostosis

Often seen in pts wtih associated syndromes like Crouzon, Apert, Saethre-Chotzen, Muenke and Pfeiffer


What type of synostosis leads to head shape called anterior plagiocephaly?

Unicoronal synostosis — d/t premature fusion of a single coronal suture —> restricted anterior growth of the skull as well as cranial base

Causes deformities of the face, ear, nose, and forehead; affected forehead is flat with contralateral side more forward. Affected side ear also more forward. Face has characteristic C-shaped deformity (base of nose drawn toward affected side and tip of nose pointing away)


Axis and plane of motion associated with frontal bone

Dual AP axis in coronal plane

Superior/inferior axis in horizontal plane

[metopic suture has “hinge-like” property. Additionally, d/t location, inferior aspect travels more laterally and medially during flexion/extension (AP axis)]


Axis of temporal bone motion

Oblique axis from jugular surface to petrous apex — no exact plane (possibly modified coronal plane)


Axes of motion and plane associated with parietal bones

2 AP axes (one through each bone) — coronal plane


A low, sloping forehead (“toboggan slide forehead”) may indicate what type of frontal bone SD?

External rotation

[a high bulging/prominent forehead aka Ski jump forehead would indicate internal rotation SD]