Head and Neck Osteology

Question 1

How is the cranium subdivided and how many bones are in each?

Answer 1

Neurocranium – 8 bones sub divided into Calvaria (top) and base of skull
Viscerocranium – 14 bones forming the facial skeleton

Question 2

What are the bones of the viscerocranium?

Answer 2

Nasal Bone, Maxilla, Mandible, lacrimal bone, zygomatic, inferior nasal concha, vomer and palatine.

Question 3

What are the bones of the Neurocranium ?

Answer 3

Parietal, occipital, temporal, frontal, sphenoid and ethmoid.

Question 4

How is the cranial floor divided up?

Answer 4

The cranial floor can be divided into the anterior, middle and posterior fossa.

Question 5

What are the immobile joints of the skull?

Answer 5

Immobile – most skull joints – joined by strong fibrous tissue such as sutures: Coronal, squamous, saggital, lambdoid, bregma, pterion and labda.

Question 6

What is the only mobile joint of the cranium?

Answer 6

Mobile – only one freely moveable joint in the skill – the temporomandibular joint

Question 7

What are fontanelles?

Answer 7

These are membranous areas of unfused skull which close in the first 2 years of life. Their function is to increase flexibility to ease passage through the birth canal and allow for brain growth.

Question 8

How can these fontanelles go wrong?

Answer 8

Clinical significance – sunken, bulging and enlarged

Question 9

What visible features are there of the cranium in a plain x-ray?

Answer 9

• Skull is made up of an outer and inner table of hard bone and between these a layer of spongy bone called diploe.
• Sella Turcica – where the pituitary gland sits
• Orbit
• Sinuses: Sphenoid, frontal, maxillary and ethmoid all visible on x-ray
• Hard Palate
• Hyoid Bone

Question 10

What is a lucid interval?

Answer 10

Lucid interval – temporarily fine after hitting head.

Question 11

What is the clinical significance of the pterion?

Answer 11

Middle meningeal artery run under the pterion which is a thinner part of the skull – if there is trauma here there is a risk of haematoma between the meninges and skull – extradural haemorrhage. You can also have epidural haemorrhage and subdural haemorrhage.

Question 12

Describe a Basilar Skill Fracture?

Answer 12

Basilar Skull fractures – trauma through the cranial floor due to transmission of force through the vertebral column. Relatively uncommon but shouldn’t miss as hard to find. Signs: meningeal tears causing leakage of the CSF and bleeding in soft tissues, Battle’s sign (bruising over mastoid process), Racoon eyes (bruising around both eyes), haemotympanum (bruising behind the ear), sinuses, cranial nerve palsies and risk of meningitis.

Question 13

Why is the cranial floor particularly susceptible to fracture?

Answer 13

The cranial floor of the skull is particularly susceptible to fracture due to the large number of foramina present in it.

Question 14

What parts make up the hyoid bone?

Answer 14

Hyoid bone is made up from its main body, the greater horn and the lesser horn.

Question 15

How many cervical vertebrae and nerve roots are there?

Answer 15

There are 7 cervical vertebrae and 8 cervical nerve roots.

Question 16

Describe C1 and C2 and how they interact?

Answer 16

C2 is the axis which is the strongest of the C spine as it bears the weight of the head through the atlas. The odontoid process or dens of C2 projects up into atlas and is held tightly to its anterior portion by the transverse ligament of atlas, preventing horizontal displacement.

Question 17

What is different about the articular surfaces of the cervical spine?

Answer 17

The articular surfaces of the cervical spine are much more horizontally orientated than in other vertebrae so they can slip off much more easily. Usually this won’t cause much damage due to the large intervertebral foramen of the C spine.

Question 18

What is the Nuchal ligament?

Answer 18

The Nuchal ligament is the continuation of the supraspinous ligament and attaches to the spinous processes of C1-C7.

Question 19

How can severe trauma injuries affect the spinous ligaments?

Answer 19

Severe trauma injuries can cause the cervical vertebral spine ligaments to rupture or tear making the spine much less stable.

Question 20

What are the general characteristics of the cervical spine?

Answer 20

Cervical vertebrae have small vertebral bodies, bifid spinous processes and contain a foramen in their transverse processes.

Question 21

What sort of scan is always carried out after severe injury to the head and neck and what should you always do to the patient?

Answer 21

With any severe injury to the head a CT scan is usually required to asses skull and soft tissue damage – must also consider cervical spine damage.

If you suspect a cervical Spine Injury always immobilise the patient.

Question 22

Describe a hangman’s fracture

Answer 22

This is casued by hyperextension of the head and the C2 body is seperated from the spinous process and inferior articular process by a fracture through the pedicles. This cuases a forward displacement of C1 and C2’s body onto C3 making the head unstable and spinal column damage is likely. If fracture extends outwards to the transverse foramen there is risk of damage to the vertebral arteries.

Question 23

Describe a jefferson’s fracture?

Answer 23

This usually occurs due to a high axial load such as diving into shallow water, car crashing, children falling on their heads etc. and results in the fracture of the anterior and posterior arches splitting the atlas into 4 parts, usually there is no neurological damage. If the transvese process is damaged it may be unstable but usually not.

Question 24

Describe the peg fracture?

Answer 24

This usually happes form a blow to the back of the head resulting in the dens to fracture off of the axis.

Question 25

What is a vertebral crush fracture?

Answer 25

Fracture of the vertebral bodies – mechanisms = many such as hyperflexion
Cervical wedge fracture – may be stable if just one vertebrae involved and loss of height of vertebral body on x-ray. Associated with spinal degenerative disease – osteoporosis

Question 26

How do degenerative diseases affect the cervical spine?

Answer 26

Osteoarthritis of the C-spine can lead to cervical spondylosis – wear and tear of C spine vertebrae. Affects older population, very common disorder. Features include: Osteophytes, facet joint hypertrophy, disc herniation, disc space narrowing and sclerosis of end plates.

Question 27

What are the complications of degenerative diseases of the cervical spine

Answer 27

Cervical Spondylotic radiculopathy
Nerve root impingement – dermatomal arm pain +/- mild weakness and sensory loss.

Cervical Spondylotic myelopathy
Spinal cord compression – loss of function, often loss of fine motor skills in upper limbs.

Question 28

What structures pass through the carotid canal?

Answer 28

Internal carotid artery and internal carotid nerve plexus

Question 29

What structures pass through the jugular foramen?

Answer 29

Inferior petrosal sinus, glossopharyngeal nerve (IX), vagus nerve (X), Accessor nerve (XI), sigmoid sinus and the posterior meningeal artery.

Question 30

Why can trauma to the scalp appear as trauma to the face?

Answer 30

Frontalis muscle doesn’t attach to bone it attaches to skin. This means in a head injury that involves the subaponeurotic blood vessels of the scalp blood can pool around the eyes and bridge of the nose making it appear as if there has been trauma here.