S2) Osteology and Radiology of the Skull and Cervical Spine Flashcards
Identify the following structures on an X-Ray of the cervical vertebrae:
- C1-C7 vertebrae
- Vertebral body
- Spinous processes
- Facet joints
- Lamina
- Pedicle
Identify the types of osteological features of skull bones
- Fossae: shallow depressions
- Canal: bony tunnel
- Foramina: round holes
- Fissures: narrow slits
The bones of the skull can be broadly divided into two groups.
Identify them
- Neurocranium (8 bones) - encompasses the brain
- Viscerocranium (14 bones) - forms the facial skeleton
Describe the function and components of the neurocranium
- Function: encase and protect the brain
- Components:
I. Calvaria
II. Cranial floor
III. Cranial cavity
Describe the development of the neurocranium
- Calvaria begin as membranes i.e. intramembranous ossification (skull cap)
- Cranial floor begin as cartilage i.e. endochondral ossification (base)
- quite a few ares remain membranous
- all the bones are very flat
Describe the function and components of the viscerocranium
- Contents: facial skeleton and the jaw
- Function: surrounds oral cavity, pharynx and upper respiratory passages
Describe the development of the viscerocranium
- Bones begin as membranes or cartilage and ossify
- Most structures develop from the pharyngeal arches (1&2)
Why are there foramina, fissures and canals in the neurocranium?
- To allow the neurocranium to communicate with other structures of the head and neck
- To allow passage of blood vessels and cranial nerves
Three ‘bowl‐shaped’ depressions form the cranial floor.
Identify them and describe their osteological features
Anterior, middle and posterior cranial fossae – each fossae has series of foramina, fissures and/or canals
What is the significance of the trilaminar arrangement of the bones of cavaria?
Confers protective strength without adding significant weight
What are sutures?
Sutures are fibrous joints which are found at intersections between bones
– all found between the 22 individual bones that form the skull
Identify the names of the most important sutures
- coronal - run between frontal and parietal bone
- sagittal - between two paired pariatal bone
- lamboid - intersection between occipital bine and two parietal bone
Describe the features of the bones forming a suture joint
Edges of bones forming suture joint are ‘serrated’ to prevent slippage and movement
Describe the development of suture joints
- Growth at sutures stops around puberty
- Then are gradually obliterated from inside → outside
What are fontanelles?
Fontanelles are large areas of unossified membranous gaps between flat bones of calvaria
- anterior
- posterior
What is the function of fontanelles?
- Allow for alteration of the skull size and shape during childbirth
- Permit growth of infant brain
When do the fontanelles fuse?
Fontanelles fuse in early infancy:
- Anterior: ~18 months ‐ 2 years
- Posterior: ~1 ‐ 3 months
What is the early fusion of fontanelles called?
Craniosyntosis is the early fusion of fontanelles and sutures so brain can’t grow to max size
Why is the anterior fontanelle clinically useful when examining babies?
Inspection and gentle palpation of anterior fontanelle can be used to assess intracranial pressure and state of hydration
- high pressure → bulge
- dehydrated → sunken
What is required to fracture a skull?
Why are the incidence in skull fractures varied?
- Significant trauma and force required to fracture skull due to trilaminar arrangement of skull
- Thickness of cranial bones varies, resistance to fracture therefore varies
What is the main concern with regards to skull fractures?
Skull fractures are associated with higher incidence of intracranial pathology (injury to brain, blood vessels, cranial nerves) and neurological deficits
Can one still have an intracranial injury without a skull fracture?
How do we confirm this?
Yes, CT scanning should be performed in all patients with known or suspected skull fractures to identify any intracranial injuries
Identify and describe the three main fracture types
- Linear fractures: fracture passes full thickness of skull, fairly straight, involve no bone displacement
- Depressed fractures: fragment is displaced inwards towards the brain
– Comminuted: multiple fractures can be depressed or not
What are fractures involving the cranial base called?
Basilar skull fractures
What are basilar skull fractures associated with?
Basilar fractures are associated with cranial nerve injuries
What is the pterion?
The pterion is the thinnest area of the skull (part of the temporal bone)
meeting point of 4 bones - parietal, frontal, greater wing of sphenoid, squamous part of temporal bone
Why are injuries to the side of the head associated with intracranial haemorrhages?
- Pterion is associated with middle meningeal artery
- Blows to side of head can fracture bone in area of pterion and injure blood vessel lying immediately below
Identify 3 other bones which are commonly fractured/injured
- Nasal bones
- Zygomatic bone and arch
- Mandible
Identify 5 distinct clinical features associated with basilar skull fractures
- Raccoon eyes – bruising around both eyes (periorbital ecchymoses)
- Battle’s sign – bruising over the mastoid process
- Haemotympanum – blood behind eardrum
- CSF rhinorrhea – cerebrospinal fluid leaking from nose
- CSF otorrhea – cerebrospinal fluid leaking from ear
Identify the frontal bone
- grows as left and right frontal bone and then fuses together
- forms the roof of the orbit → orbital plates
- part of the anterior cranial fossa and forms the boundary of the anterior cranial fossa
Identify the parietal bone
- flat bone
- paired we have a left and a right
- damage to this bone can cause damage to the ear
Identify the occipital bone
- occipital condoles which meet with the first cervicle vertebra
- from behind has the external occipital protuberance and superior nucheal line causing the arcs
- hole → foramen magnum where the brainstem continues as the spinal chord
Identify the sphenoid bone
- you can only see the greater wing of the sphenoid when looking at the skull
Identify the temporal bone
- has a flat part forming vault of skull
Identify the maxilla bone
Identify the mandible bone
Identify the zygoma bone
Identify the nasal bones
Identify the ethmoid bone
- forms top of nasal cavity
- it has lots of air filled cavities (numeratised)
- perpendicular plate splits the nasal cavity in half
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Identify the lacrimal bone
Identify the following osteological landmarks on the skull below:
- Ethmoid bone
- Infraorbital ridge
- Infraorbital foramen
- Middle nasal concha
- Inferior nasal concha
Identify the following osteological landmarks on the skull below:
- Supraorbital ridge
- Lacrimal fossa
- Nasal bone
- Supraorbital foramen
- Orbital plate
Identify the following osteological landmarks on the skull below:
- Superior orbital fissure
- Perpendicular plate
- Zygoma
- Vomer
Identify the following osteological landmarks on the skull below:
- Maxilla
- Alveolar process
- Mandible
- Mental foramen
- Mental protuberance
Identify the following osteological landmarks on the skull below:
- Condyloid process
- Ramus
- Zygomatic process of temporal bone
Identify the following osteological landmarks on the skull below:
- Styloid process
- Mastoid process
- Petrous part
- Squamous part
- Superior nuchal line
Identify the following osteological landmarks on the skull below:
- External auditory meatus
- Head of mandible
- Body of sphenoid
- Articular fossa for mandible
- Lacrimal bone
Identify the following osteological landmarks on the skull below:
- Frontal process of maxilla
- Zygomatic arch
- Zygomatic process of maxilla
- Coronoid process
Identify the following sutures on the skull below:
- Bregma
- Lambda
- Coronal suture
- bregma is in between sagittal and coronal suture
- intersection between sagittal and lambdoid suture is lambda
- in fetal skull these remain membranous to allow for bone growth
Identify the following osteological landmarks on the skull below:
- Sagittal suture
- Superior temporal line
- External occipital protuberance
Identify the mandibular foramen on the skull bone below
Identify the following osteological landmarks on the skull below:
- Crista galli
- Cribiform plate
- Anterior clinoid process
- Posterior clinoid process
- Foramen lacerum
Identify the following osteological landmarks on the skull below:
- Cribiform foramina
- Optic canal
- Hypophyseal fossa
- Lesser wing of sphenoid
- Greater wing of sphenoid
Identify the following osteological landmarks on the skull below:
- Foramen rotundum
- Internal acoustic meatus
- Hypoglossal canal
- Petrous part
Identify the following osteological landmarks on the skull below:
- Superior nuchal line
- Hypoglossal canal
- Articular condyles for atlas (C1)
- Foramen ovale
- Temporal fossa
Identify the following osteological landmarks on the skull below:
- Lateral pterygoid plate
- Medial pterygoid plate
- Palatine process
- Base of sphenoid bone
- Clivus
Label structures A, B, C and D in the image below
- A – Foramen rotundum
- B – Foramen ovale
- C – Internal acoustic meatus
- D – Jugular foramen
Label structures E, F and G in the image below
- E – Foramen lacerum
- F – Foramen spinosum
- G – Carotid canal
bones of the calvaria
These bones all form the calvaria:
- parietal
- frontal
- occipital
all of these are flat with a curved surface
- all provide protection
periosteum
- wrap themselves over the bones of the skull
- The middle meningeal artery runs between the periosteum and bone → if it starts to bleed then it forms an extradural haemorrhage
- it starts to strip the periosteal layers off the bone but once it reaches the sutures it stops peeling away
periosteum
- wrap themselves over the bones of the skull
- The middle meningeal artery runs between the periosteum and inner table of bone → if it starts to bleed then it forms an extradural haemorrhage
- it starts to strip the periosteal layers off the bone but once it reaches the sutures it stops peeling away
What is the role of the petrous part of the temporal bone
houses the structures of the middle and inner ear
bones forming the anterior cranial floor
- frontal bone (anterior)
- ethmoid bone (in the middle of the frontal bone
- posterior part of fossa is made up of the lesser wing of the sphenoid bone
bones forming the middle cranial floor
- sphenoid bone - greater wings
-
sella turnica
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bones forming the posterior cranial fossa
- temporal bone
- occipital bone
when fracture involving skull what type of imagining would you use
- CT
If someone had an injury involving the facial part what type of imagining would you use
- xray
what bones that make up the facial part of the head are most likely to be fractured?
- nasal bones
- zygomatic arch and bone
- mandible
temporomandibular joint and its innervation
- synovial hung type joint
- can get TMJ pain, dislocation and arthritis
- innervated by auriculotemporal nerve (branch of the mandibular division of the trigeminal nerve)
anatomy of the TMJ
- temporalis muscle inserts into the coronoid process
- have inferior and superior joint capsule
how is the TMJ stabilised
- joint capsule around the joint
- extra capsular ligaments
role of the inferior and superior joint capsule of the TMJ
- inferior → rotation of the head
- superior → gliding forward and protraction
muscles involved in moving the mandible:
- elevation
- depression
- protrusion
- retraction
- grinding
dislocation of the TMJ can be caused due to:
- facial trauma (yawning)
- jaw locks due to anterior dislocation of the articular tubercle
- contraction of muscle around joint can keep it in a locked position
superior orbital fissure
transmits lots of nerves
which area transmits the optic nerve ?
optic canal
which are transmits maxillary division of the trigeminal nerve?
foramen rotundum
which area transmits the mandibular division of the trigeminal nerve
foramen ovale
Which area is filled with cartilage
foramen lacerum
- the internal carotid artery traverses over the top of it during its course, just as it exits the carotid canal
what is the name of the structure that transmits the middle meningeal artery
foramen spinosum
what area transmits the internal carotid artery
carotid canal
what vessel is a continuation of the sigmoid sinus
internal jugular vein
what is the role of the concha in the ethmoid bone?
- it makes air flow into the nose turbulent so that there is more time for the air to be humidified
