4 - Osteology of the Skull Flashcards
How can we divide the bones of the head up?
- Cranium: Neurocranium (vault, floor, cavity) and Viscerocranium
- Mandible
In broad terms how do each part of the cranium form embryologically?
What is the structure of the calvaria?
- Trilamina
- Two layers of compact bone separated by a layer of spongy bone called the diploe
- Adds strength without adding significant weight
Label the bones of the calvaria part of the neurocranium
Label the important joints of the calvaria.
Bregma and Lambdoid are where the fontanelles wrere as an infant. They are points of intersection between different sutures.
What are the different types of skull fracture?
- Linear fractures radiate away from the point of injury
- Comminuted can be depressed or non-depressed
- Basillar have signs (see later flashcard)
What is a fontanelle and where are they found?
- Large areas of unossified membranes between flat bones of the calvaria
- Allow for alteration of skull and brain size and birth
- Anterior fuses 18months-2years, Posterior fuses 1-3months
What can fontanelles be used for?
Anterior: slightly convex in infant, can palpate to assess intra-cranial pressure and hydration state.
- If baby crying or vomiting and it is bulging this is normal, if not crying not normal
- If sunken may be dehydrated
What is craniosynostosis?
- Early fusion of fontanelles and sutures
- Head can have an usual shape and may need surgery to reshape it
How does the periosteum of the skull run and what is the importance of this anatomy?
- Covers inner and outer table of the skull, strongly adhered to edges of suture and continous through sutures
- Fracture to pterion can blow middle meningeal artery (anterior branch), haemorraghe pulling periosteum away from the bone up to the sutures
How is the cranial floor divided up?
- Anterior Fossa: frontal, ethmoid and small bit of sphenoid
- Middle Fossa: sphenoid and temporal
- Posterior Fossa: occipital
Where is the ethmoid bone and label it’s different parts.
Label the parts of the sphenoid bone.
Label the parts of the temporal bone.
Label the parts of the occipital bone.
What should we do if we suspect a skull fracture and why?
- CT scan as significant force and trauma needed for a fracture so may be injuries intracranially
- Even if no fracture could still be something going on intracranially after head trauma so need to look at cervical spine, brain, look in ears and behind ears, neurological assessment
What type of fractures are these CT scans showing?
- Comminuted has mutiple fracture lines and bone displacement inwards but linear does not
- Main concern is brain not fracture
What are some signs of a basilar skull fracture and what fossa would be fractured in each case?
- Rhinorrhea or CSF fluid leakage from nose
- Battle’s = bruising over mastoid
Label the bones of the viscerocranium.
Frontal bone forms part of the orbit (supraciliary arch), cranial floor and calvarium
What injury would occur if there was trauma to the top of the orbit and why?
Skin would splinter over the supraciliary arch (supraorbital ridge) with blunt force injury
What are the most common fractures of the face?
Zygomatic bone and arch, mandible and nasal bones. Maxillae rare
When looking at a mandible x-ray with a suspected fracture what should you think about?
There is usually two fracture lines
What is the anatomy of the TMJ joint and what is it innervated by?
- Synovial hinge joint
- Disc splits the joint into two
- Innervated by auriculotemporal nerve (mandibular division of trigeminal Vc). This nerve also sensory which is why pain radiates here
What is TMJ disorder?
- Pain around jaw, ear and temple
- Clicking, poppingm grinding when moving jaw
- Lock jaw
- Headache around temples
- Pain mostly due to ear so this can throw you off
What are some conditions affecting the TMJ?
- Arthritis
- TMJ disorder
- Dislocation
What movements can the TMJ do and what muscles perform these movements?
Condyle does not pass in front of the articular process
How does the TMJ dislocate and how do you reduce it?
- Facial trauma (particularly open mouth side of face) and yawning
- Jaw locks in open position as condyle moves anterior over articular tubercle
- Pterygoids and mastication muscles spasm and pull forward locking it
How do you classify midfacial injuries and why are they concerning?
Le Fort Classification
Fractures can seperate face from skull base so issues with patients airways
Where does the carotid sheath extend to and from?
Base of skull to aortic arch
Where is the cribriform plate?
Where is the orbital plate of the frontal bone?
Label this AP x-ray of the cervical vertebrae and how would you get a better view of C1 and C2?
Open mouth image
By what process do the fontanelles ossify?
What features of a fetal skull are different to an adult skull?
