Head and Neck: Osteology of the Skull

Question 1

Name the 8 bones of the neurocranium

Answer 1

1 ethmoid bone
1 frontal bone
1 occipital bone
2 parietal bones
1 sphenoid bone
2 temporal bones

Question 2

Name the 14 bones of the viscerocranium

Answer 2

Inferior nasal concha (2)
Lacrimal bones (2)
Mandible
Maxilla (2)
Nasal bones (2)
Palatine bones (2)
Vomer
Zygomatic bones (2)

Question 3

What are the mobile joints of the skull?

Answer 3

There is only 1: the temporomandibular joint which opens the jaw

Question 4

Name the sutures (and state which bones they join)

Answer 4

• Coronal suture between the frontal and parietal
• Squamous suture between the temporal and parietal
• Saggital suture between the 2 parietal bones
• Lamboid suture between occipital and parietal

Question 5

Name the anatomical landmarks of the skull at the suture junctions

Answer 5

• Bregma - located at the junction between the coronal and saggital sutures
• Pterion - located at the junction between the coronal and squamous sutures
• Lambda - located at the junction between the lamboid and saggital sutures

Question 6

How many cervical vertebrae and nerve roots are there?

Answer 6

7 vertebrae and 8 nerve roots (normally nerves arise above the vertebrae but C7 has a nerve above and below)

Question 7

What are the layers of the skull bone

Answer 7

There is an outer and inner table made of cortical bone and diploe inbetween which is cancellous bone

Question 8

What is the sella turcica?

Answer 8

A depression in the body of the sphenoid bone

The deepest part is the hypophyseal fossa where the pituitary is located

Question 9

What bones make up the hard palate?

Answer 9

The maxilla and palatine bones

Question 10

What imaging modality do you use for a suspected skull fracture and why?

Answer 10

CT scan - good for looking at both bones and brain. It isnt the fracture that is of concern, more the potential damage to the brain

Question 11

What lies under the pterion?

Answer 11

The pterion is a thin area of bone

Immediately under it is the middle meningeal artery - a big cause of brain bleeds

Question 12

What are the signs of a basilar skull fracture?

Answer 12

• CSF running out the nose
• blood behind the ear drum
• bilateral bruising around eyes
• mastoid bruising

Question 13

Whats a jeffersons fracture?

Answer 13

A burst fracture of C1 - both ant and post arches are fractured
Often caused by axial compression eg diving into shallow water
It can be unstable and damage the transverse ligament of atlas

Question 14

What is a hangmans fracture?

Answer 14

A bilateral fracture of the posterior arch of C2 and disruption of the C2-3 junctions
Its caused by hyperflexion of the neck - can be caused by hanging but more commonly hitting the windscreen if not wearing a seatbelt
There is a high risk of C2 displacement and spinal chord damage

Question 15

What is cervical spondylosis?

Answer 15

Osteoarthritis of the C spine causing bony spurs, disc herniation, disc space narrowing, sclerosis of end plates
Very common in elderly

Question 16

What is cervical spondylotic radiculopathy and myopathy?

Answer 16

Cervical spondylotic radiculopathy - nerve root impingement, causes dermatomal pain, sensory loss and mild weakness
Cervical spondylotic myopathy - spinal cord compression, causes loss of function and loss of fine motor skills in arms

Question 17

What are frontanelles and why are they important?

Answer 17

Areas of the skull that have not yet fused so are soft

They allow growth of the brain and allow the head to be compressed during birth

Question 18

At what age do the frontanelles fuse?

Answer 18

Anterior frontanelle: usually 9-18 months

Posterior frontanelle: usually 1-2 months

Question 19

How might the presence of the fontanelles be helpful when assessing an
unwell newborn or infant?

Answer 19

The frontanelles can be sunken if dehydrated, bulging if there is raised intracranial pressure and to large if the baby was premature

Question 20

How is the feral skull different from the adult skull?

Answer 20

• disproportionally large cranium
• Bones not completely ossified and are smooth
• No mastoid process
• The two halves of the mandible are not yet fused
• Frontanelles