Osteology and Radiology of the Skull and Cervical spine Flashcards
Which regions of the spine maintain the primary and secondary curvature?
Primary: Thoracic, sacral and coccygeal
Secondary: cervical and lumbar
What are the seven processes (projections) off the vertebral arch?
1 Spinous process
2 transverse processes
2 articulate processes
What is another term for an articulate process?
Zygapophyses
Name three primary functions of the cervical spine
- Support skull
- Allow for skull movement
- Transmit nervous and vascular structures
How many spinal nerves and cervical vertebra do you have?
8 spinal nerves and 7 cervical vertebra
Describe the characteristics of a typical cervical vertebra
Smallest of the vertebra
- bifid spinous process
- transverse foramen IN transverse process which allows for a conduit for vertebral artery and vein
- Large triangular vertebral foramen to allow for innervation of the upper limb
- small dome shaped body
What are uncinate processes and what is their function?
They are the upward lips of the edges of the cervical vertebra’s body and they restrict the amount of lateral flexion that can be done by the cervical vertebra
Which cervical vertebra are atypical? What are their ‘special names’ if any?
C1: ATLAS
-no body and no spinous process
C2: AXIS
-has an odontoid process called dense (which articulates with a facet on C1)
C7: no special name :(
- no bifid spinous process and no transverse foramen in its transverse processes
- spinous process called vertebral prominence (extra long)
Name the ‘3 lines of the cervical region’ from anterior-posterior
- Anterior
- Posterior
- Spinolaminar
What is a fracture of the atlas called? How might it occur and how does it typically present?
Jefferson’s fracture (C1)
Head first fall from height (i.e diving into pool)
Pain but typically no neural signs
What is a fracture of the axis called? How might it occur and how does it typically present?
Hangman’s fracture (C2)
Hyper extension of the head on the neck
Which bones compose the skull?
Cranium + mandible
Which joint is the ONLY movable joint of the skull in an adult and where is it?
Temperomandibular joint
The articulation between the mandible (jaw) and the cranial base
What are sutures?
Fibrous joints which interlock the bones that compose the skull
How many bones are there in the skeleton of the head?
22 discrete bones
Name three general functions of the skull
- Encloses/protects brain and special sensory organs (Estes, ears, tongue, nose)
- Creates specialized environment for brain to thrive
- Site for muscle attachments and meninges
Which areas of the cranium are especially thick and especially thin?
Thick: occipital and frontal bones
Thin: pterion, squamous part of temporal bone (covered by thick muscle)
Which bones does the cranial bone form? What lies between them?
Cranial bones form the calvaria (vault of the neurocranium) and the cranial base.
The Cranium has a tri-lamina bony structure
2 plates of thick and resilient compact bone (an outer and inner plate)
1 middle layer of spongy bone/ “diploe layer” which reduces the weight of the cranium
Describe the overall structure of the mandible
Formed by the union of R and L mandible bones joined by the mental symphisis (midline fibrous joint)
Which part(s) of the mandible do and don’t articulate with the skull?
Does articulate with skull: Condylar process
Doesn’t articulate with skull: coronoid process
What makes the sutures of the skull especially strong?
Bony edges are serrated which allows them to interlock (making it less likely for them to easily unlock when force is applied in one direction)
Name the four sutures that join the cranium and the three ‘points’ where the sutures join
Sutures: coronal, sagittal, lambdoid, squamous
Sutures join at the:
- Bregma: coronal and sagittal
- Lambda: lambdoid and sagittal
- Pterion: joins temporal, frontal, parietal and occipital bones
What are the cranial fossa? Name them and the nerves associated with them
The floor of the cranial cavity is divided into three depressions/fossa
- Anterior fossa: CN I and II
- Middle fossa: CN II-VI
- Posterior fossa: CN VII-XII
Where is the CNII foramen?
On the junction between the anterior and middle fossa
What determines the number of a cranial nerve?
CN are numbered 1-12 based on how they exit the cranial base from an anterior-posterior direction
Which bones are associated with the anterior cranial fossa?
Frontal, ethmoid and sphenoid
Which holes are associated with the anterior cranial fossa and what are their associated nerves?
Olfactory foramina in cribriform plate (CNI) Optic canal (CNII)
Which bones are associated with the middle cranial fossa?
Sphenoid and temporal
Which holes are associated with the middle cranial fossa and what are their associated nerve(s) and/or vessel(s)?
- Superior orbital fissure: “Live frankly to see absolutely no insult”
-Lacrimal and frontal divisions of ophthalmic nerve V1
-Trochlear n IV
-Superior division of oculomotor n III
-Abducens VI - Foramen rotundum (CN V2 - maxillary nerve)
- Foramen ovale (CN V3 - motor/muscles of mastication)
4, Foramen spinosum (MMA enters the cranial cavity via this foramen)
Which bones are associated with the posterior cranial fossa?
Temporal, occipital and bits of sphenoid and parietal
Which holes are associated with the posterior cranial fossa and what are their associated nerve(s) and/or vessel(s)?
- Foramen magnum - spinal cord and spinal roots of the accessory nerve (CN XI)
- Internal acoustic meatus (CN VII, VIII - vestibulocochlear n (transmits sound from inner ear to brain))
- Jugular foramen (CN IX, X, XI) + Internal jugular vein
- Hypoglossal canal (CN XII - hypoglossal n to the tongue)
What is the major opening of the skull?
Foramen magnum
Where does the facial nerve exit the skull?
*Where does its come from directly prior and what does it do right after?
Comes from the internal acoustic meatus and through the middle ear and then out the stylomastoid foramen!
*the foramen is between styloid and mastoid processes of the temporal bone
It then passes through the parotid gland and gives off 5 branches (to Zanzibar by motor car)
Why is the cranial base at an increased risk of fracture?
As there are a large number of foramina on the skull floor/cranial base which weakens it
Which general nerves enter and exit the foramina at the cranial base?
Enters: sensory and sympathetic fibres
Exits: motor and parasympathetic outflow
What does the frontal bone form?
The upper border of the orbital margins and roof of orbit
Where is the ethmoid bone and what nerve does it allow passageway of to the brain?
Ethmoid bone is NESTED in the midline in the anterior fossa and allows for passage of olfactory nerve CNI from nasal mucosa to the brain (through the holes in the cribriform plate and crista galli)
What is the topmost part of the ethmoid bone?
What symptoms could a damaged ethmoid lead to?
Crista galli
Poor sense of smell (if olfactory nerve is separated), nose bleeds and CSF leak
Which bone of the skull is ‘bat shaped’? Where is it and which sinuses does it contain?
Sphenoid bone; sits at the upper aspect of the nasal cavity
Contains the sphenoid sinuses (most posterior of the paranasal sinuses)
Which nerve and vessel threads through the sphenoid bone?
Optic nerve and ICA
Describe the parts of the sphenoid bone
Has a lesser and greater wing and a central body
Which structures are found within the central body of the sphenoid bone?
The sphenoidal sinus and the pituitary gland
What structure forms a cup around the the pituitary gland?
The sella turcica (in the median portion/central body of the sphenoid)
What part of the skull does the parietal bone compose?
Large part of cranial roof and walls
What can be found along the internal surface of the parietal bone?
- Grooves of MMA
- Sagittal sulcus
- Granular pits (from CSF valves)
- Grooves for sigmoid sinus
What does the external surface of the parietal bone serve as?
An attachment point for muscles (i.e temporalis - muscle for mastication)
Which specific bone of the skull does the facial n CN VII pass? Generally what other organs does this bone protect?
The petrous bone of the temporal bone (stylomastoid foramen)
The temporal bone also protects organs of hearing and balance
Name the 6 parts of the temporal bone, identify which is very thin/weak and which is very stony/hard
- Squamous: VERY thin and weak
- Mastoid
- Tympanic
- Styloid process
- Zygomatic process
- Petrous: stony/hard
Describe what surrounds foramen magnum
4 parts of the occipital bone
- Squamous: posterior part
- TWO condyles R and L
- Basilar: anterior part
What is the difference between a neonatal vs adult skull?
Mobility and rigidity:
- Neonate: cranial sutures are not interwoven and have great mobility (partly to get the head out of the pelvis)
- Adult: sutures fused and joints don’t move
Different proportions between neurocranium and viscerocranium
- Neonate: 8:1
- Adult: 2:1
A neonate has anterior and posterior fontanelles (spaces where ossification isn’t complete)
Alveolar processes (of maxilla) and paranasal sinuses are underdeveloped at birth
What structure runs deep to the anterior fontanelle? What else can be inferred about the baby by its anterior fontanelle?
The superior sagittal sinus
Can indicate low hydration levels if the anterior fontanelle is sunk in
How might a basal skull fracture present?
Battle’s sign: bruising over mastoid process (behind ear) due to extravasated (leakage) of posterior auricular artery
Panda/Racoon eyes: periorbital (around the eyes) ecchymosis
Which part of the brain is often fractured to result in battle sign?
The middle cranial fossa
What can happen if a fracture remains infused/unsealed as the child’s skull grows?
The fracture also grows
What is a ping pong fracture and why does it occur?
A depressed skull fracture in an INFANT skull caused by the inner buckling of the calvarium due to the soft and resilient nature of their bones
How does an orbital blowout fracture happen? How might it then appear on a CT scan and why?
Traumatic deformity of the orbital floor or medial wall (typically from the impact of an object larger than the orbital aperture or eye socket)
Contents (greyness) in the maxillary sinus, because…
*Remember bones of orbit (particularly medially (lamina papyracea) and inferiorly) are very thin and so orbital contents will herniate DOWN into the maxillary sinus
Which bones of the cranium articulate with the 1st cervical vertebra?
Bones of the cranial base: facial skeleton and mandible
Which type of fracture does trauma to the vault often result in?
Radiating linear fractures (away from the point of impact)
What is characteristic of a countrecoup fracture?
Fracture occurs on the opposite side of the cranium rather than the site of impact
Which bones compose the facial skeleton?
The mandible and maxilla
Which bones does the frontal bone articulate with?
Inferiorly: Nasal and zygomatic bones
Lacrimal, ethmoid and sphenoid bones
What does the frontal bone form?
The skeleton of the forehead
The rood of the orbit
Part of the floor of the cranial cavity
Which bones does the zygomatic bone articulate with?
Medial superiorly: frontal bone
Medially: sphenoid
Medial inferiorly: maxilla
Lateral: temporal bone
What are the following traumas likely to result in? A) The most common facial fracture B) Massive facial trauma C) Hard blow to the lower jaw D) Trauma to the supraciliary arches
A) involves nasal bones
B) Maxillofacial fracture
C) Fracture of neck of mandible, possibly with dislocation of temporomandibular joint
D) profuse bleeding/bruising around the orbit -> causes tissue fluid and blood to accumulate in the surrounding CT -> “black eye”
Name the joint facilitating the atlas’s support of the skull?
Atlanto-occipital joint
Which cervical vertebra is the strongest and why?
The axis (C2) because C1 which carries the skull rotates on it
What holds the odontoid process/dens in place to prevents its horizontal displacement?
A transverse ligament of the atlas
What do the transverse processes of cervical vertebra “end in”
Two lateral projections, each projection has an anterior and posterior tubercle
What are the anterior tubercles of C6 referred to as and why?
Carotid tubercles because the common carotid arteries may be compressed against them to control bleeding/
What is most likely to happen when a force is applied to the cervical vertebra?
More likely to dislocate (due to their stacked nature) rather than fracture
What causes neck pain in older age?
Shrinkage of the IV discs causes narrowing of the intervertebral foramina which can compress the spinal nerve roots
Where are the most common sites of cervical spine injuries? Where do the most fatal injuries occur?
C2, C6 and C7
Most fatal injuries occur at the craniocervical junction; inferior skull, atlas and axis
What might severe hyperflexion of the cervical region result in? Provide one example of how this might occur
*including where pain is likely to be felt
Ex: Head-on collision
- Rupture of lower cervical IV discs, i.e C5/6 and C6/7 which can compress spinal roots C6 and C7
- Pain in the neck, shoulder, arm and hand
What might severe hyperextension of the cervical region result in? Provide one example of how this might occur
*including where pain is likely to be felt
Ex: rear-end collision
1. Tearing of anterior and posterior longitudinal ligaments
2. Fracture of cervical spinous processes
3. Disc rupture
And blood vessel injuries
How might osteoarthritis result in pain and muscle spasms?
It affects the facet joints of the vertebral arches (zygopophyseal joints). Due to their close nature to the intervertebral foramina (where spinal nerves emerge from the vertebral canal), the related spinal nerves are affected causing
1. Pain along the distribution patterns of the dermatomes 2. Spasms in the muscles derived from the associated myotomes
What might the displacement of a fractured dense result in?
Displacement of the fractured dense can
- Injure the spinal cord -> quadriplegia (paralysis of all limbs)
- Injure the medulla -> death
Name the four major types of skull fractures
- Linear (hairline)
- Depressed
- Compound
- Basilar
What defines a simple fracture?
Break in the bone without damage to the skin
Describe a linear and a depressed fracture?
Linear: break in cranial bone resembling a thin line with NO depression/distortion of the bone
Depressed: break in cranial bone with depression of the bone in towards the brain and is often communited (multiple pieces)
What is involved in a compound fracture?
Break in or loss of skin and splintering of the bone accompanied by brain injury and bleeding
Which part of the skull is involved in a basilar fracture?
The base of the skull
Which anatomical sites is the Skull prone to fracture?
- Squamous temporal and parietal bones over temples
- Sphenoid air sinus
- Foramen magnum
- Inner parts of sphenoid wing at skull base
Which parts of the posterior cranial fossa are more likely to fracture?
Areas between the mastoid and dural sinuses
Which cranial fossa is weakest and why?
The middle cranial fossa due to thin bones and multiple foramina
Which cranial fossa is weakest and why?
The middle cranial fossa due to thin bones and multiple foramina
List 13 signs or symptoms for skull fractures
BBDDVVCCCSSSH
Bebe don’t dress very vivaciously! Somebody stop summer cause can’t control her
- Bleeding from: wounds, ear, nose
- Bruising around eyes
- Drainage of CSF from ears or nose
- Drowsiness
- Vomiting
- Visual disturbance
- Swelling
- Slurred speech
- Stiff neck
- Confusion
- Convulsions
- Loss of consciousness
- Headache
Which spinal nerve is more likely to be affected in a C4/C5 prolapse?
C5 as it more often affects the spinal nerve below
*but C4 would be affected if the prolapse was lateral
Why might a posterior prolapse of the IV disc between C2/3 be fatal?
The phrenic nerve comes out below (C3-5) which supplies the diaphragm and if damaged will cease breathing
Which part of the skull is so thin it’s practically see-through? What is the danger of this?
Lamina papyracea or orbital lamina of the ethmoid bone
An infection in the sinuses between the eyes (such as sinusitis) may easily spread into the eye potentially causing orbital cellulitis
How might enlargement of the pituitary present and why?
Vision problems (especially problems with vision fields) as the optic chiasma is directly above and the optic nerve goes straight over the pituitary
Nerves controlling eye movement also lie on the side of the pituitary (and so do the internal carotid arteries)
Which vessel passes superiorly to foramen lacerum? What passes through foramen lacerum?
ICA (as it emerges from its obliquely lying carotid canal)
Nothing passes through, it’s filled with cartilage :)
Which fissure separates the greater and lesser wings of the sphenoid?
The superior orbital fissure
How might an orbital blowout fracture present? (Other than the obvious black eye)
Double vision: due to damage of orbital muscles
Which suture is between the parietal and occipital bone?
Lambda
Which nerve is most likely to be damaged during a forceps delivery and why?
The facial nerve: as it exits the stylomastoid foramen but the mastoid air cells don’t develop until the 2nd or 3rd year, therefore the small mastoid process leaves the facial nerve exposed
How is the neonatal skull designed to accommodate the birthing process?
- Open sutures and fontanelles allow moulding during birth
- Cranial bones can slide across each other/overlap
What is a metopic suture and when is it present?
Vertical fibrous joint dividing the two halves of the frontal bone in a newborn (rarely persists to adult)
Where is ligamentum nuchae and what is its function?
Found in the cervical region as a continuation of the interspinous and supraspinous ligaments of thoracic and lumbar vertebrae
Attaches the external occipital protuberance and the posterior border of foramen magnum to the spinous processes of cervical vertebra to preserve the normal curvature of the cervical spine
Why are cervical vertebra prone to dislocation in whiplash injuries?
Due to their almost horizontal alignment of articulate facets (between successive vertebra)
Identify whether the following bones are part of the neurocranium or viscerocranium A) Frontal bone B) zygomatic arch C) maxilla D) mastoid process E) pterion F) nasal bones
A) N B) V C) V D) N E) N F) V
