Anatomy and pattern recognition of the skull, facial bones and teeth Flashcards
Bony anatomy of the skull and associated joints
Bone classification of the skull
Cranial bones - mainly flat for cranium
parietal bones, temporal bones, frontal bone, occipital bone, ethmoidal bone and Sphenoid bone
Facial bone - irregular
mandible, maxillary bones, zygomatic bones and orbit
Bones of the skull
Most complex bony structure, l
the skull can be divide into 2 sets of bones, those of the cranium (cranial bones) and Facial bones.
Most of the skull bones are flat.
Skull bones in the adult are firmly locked by sutures. Main sutures are Sagittal, Coronal and Lambdoid sutures. Additional small sutures sphenoparietal, frontozygomatic and occipitomastoid,
The interior of the skull is divided into 3 fossae, anterior, middle and posterior.
Provide points of entry and exit to the skull through foramina and fossae.
What are the Cranial bones?
Cranial bones provide:
muscle attachment.
protection for the brain, and organs of hearing and balance.
Cranium formed by 8 cranial bones:
Paired:
parietal bones (2)
temporal bones (2)
Unpaired:
Frontal bone (1)
Occipital bone (1)
Ethmoidal bone (1)
Sphenoid bone (1)
What are the Parietal bones?
Form large part of the roof of the cranium (superior and lateral aspect of the skull). Curved and rectangular in shape. The 4 largest sutures occur where the parietal bones articulate.
Articulation:
Frontal bone – Coronal suture
Parietal bone – Sagittal suture
Occipital bone – Lambdoid suture
Temporal bone and Greater wing of sphenoid – Squamous suture
Features
Internally contains grooves for middle meningeal arteries.
Temporal ridges (superior and inferior)
Sagittal sulcus
What is the occipital bone?
Forms posterior wall of the skull
Internally forms the posterior cranial fossa
Divided into 3 parts - Squamous, lateral and basilar
Features
Foramen magnum
Externally
External occipital protruberence
External occipital crest
Occipital condyle
Superior nuchal line
Median nuchal line
Inferior nuchal line
Internally
Internal occipital protruberence
Internal occipital crest
Transverse sulcus - groove for transverse sinus.
Groove for sigmoid sinus
Jugular process
Articulates with
Parietal bone
Temporal bone
Sphenoid bone
1st cervical vertebra
What are the temporal bones?
Form the infero–lateral aspects of the skull.
Contains three main regions
Squamous,
Tympanic,
Petromastoid
mastoid,
petrous.
Squamous region
Thin portion of bone.
Articulates with
the parietal bone.
The sphenoid
the mandible
Features
Zygomatic process, with the zygomatic bone forms the zygomatic arch.
Articular fossa
Articular tubercule
Tympanic region
Feature
External auditory meatus.
Styloid process
Temporal bones: Squamous region
Thin portion of bone.
Articulates with
the parietal bone.
The sphenoid
the mandible
Features
Zygomatic process, with the zygomatic bone forms the zygomatic arch.
Articular fossa
Articular tubercule
Temporal bones: Tympanic region
Feature
External auditory meatus.
Styloid process
Temporal bones: Mastoid part
Features
Mastoid process
Mastoid notch
Mastoid foramen
Sigmoid sulcus
Temporal bones: Petrous
Looks like a miniature mountain ridge.
Posterior slope lies in the posterior cranial fossa. Anterior slope is in the middle cranial fossa
Articulates with the
Occipital bone posteriorly
Sphenoid bone anteriorly
Features
Contains middle and inner ear cavities. Housing organs of hearing and balance.
Arcuate eminence
Internal auditory meatus
Stylomastoid foramina
Carotid canal
Jugular fossa
Foramen lacerum
What is the Sphenoid bone?
Butterfly-shaped bone. Spans the with of the middle cranial fossa. Forms the central wedge and as such considered key stone of the cranium.
Articulates with all the other cranial bones
The sphenoid bone consists of:
Body centrally (contains sphenoid sinus) Posterior aspect forms the dorsum sellea that culminate to the posterior cliniod processes
Greater wing of sphenoid
Lesser wing of sphenoid project posteriorly to form the anterior clinoid processes
Pterygoid processes – project inferiorly from body, anchor muscle for chewing
Features.
Sella turcica (Pituitary fossa) Hollowed out forming a deep depression.
Anterior clinoid processes
Posterior clinoid processes
Optic foramina
Optic groove
Foramen ovale
Foramen spinosum
Foramen rotundum
Superior orbital fissure
Pterygoid canal
`what is the Ethmoid bone?
Delicate bone. Contains ethmoid sinuses
Features
Cribiform plate – forms roof of nasal cavity. Punctured by tiny holes called olfactory foramina allow the passage of olfactory nerves to the smell receptors in the nasal cavity in the brain.
Perpendicular plate – forms superior part of nasal septum.
Lateral mass – either side of the perpendicular plate containing ethmoid sinuses
Crista gali – projects superiorly from the cribiform plate is a process. Dura mater outer covering of the brain is attached to this area, helps secure the brain.
Articulates with
Sphenoid bone
Frontal bone
Lacrimal bone
Palatine bone
Vomer
Nasal bone
Maxilla
What are facial bones?
Form the framework of the face:
Contain cavities for the sense organs (sight, taste, smell)
Provide opening for food; and air entry and exit
Secure teeth
Act as an attachment for muscle.
Bones:
Inferior nasal concha (Paired) – forms part of nasal cavity
The vomer (Single) – forms part of nasal septum
The Nasal bone (Paired) – forms the bridge of the nose
The Lacrimal bone (Paired) – form part of orbit
Palatine bone (Paired) – forms part of nasal cavity and a small part of the orbit. Posterior part of hard palate
Mandible (Paired)
Maxillary bones (Paired)
Zygomatic bones (Paired)
what are maxillary bones?
All facial bones with the exception of the mandible articulate with it.
Form the upper jaw and the central portion of the facial skeleton
Features
Alveolar margin - contains sockets in which the upper teeth are embedded.
Palatine process – forms anterior part of the hard palate
Frontal process – articulates with the frontal bone
Maxillary sinus – air filled cavity within the maxillary bone. Largest of the paranasal sinuses
Zygomatic process – articulates with the zygomatic bone
Infra orbital foramina – permits nerves (zygomatic and maxillary to pass) and blood vessels to the face.
Anterior nasal spine – located immediately below the nasal aperture.
What are zygomatic bones?
Irregular shape. Form the cheek commonly referred to as the “cheek bone”.
Features
Frontal process - articulates with frontal bone.
Temporal process – zygomatic process of the temporal bone.
Also articulates with the maxillary bone inferiorly.
What is an orbit?
Formed by:
Frontal bone
Maxillary bone
Ethmoid bone
Lacrimal bone
Palatine bone
Lesser wing of sphenoid
Greater wing of sphenoid
Zygomatic bone
Features:
Superior orbital fissure
Inferior orbital fissure –
Optic foramina – passage of optic nerve
What is the mandible?
U shaped bone. Largest strongest bone of the face.
Features
Body
Ramus
Mandibular angle
Mandibular notch
Coronoid process
Mandibular condyle
Alveolar margin - contains sockets in which the lower teeth are embedded.
Symphysis Menti or Mandibular symphysis – Line of fusion of the two mandibular bones.
Mental foramina
Mandibular foramina – located on medial surface of each ramus.
Oblique (ridge) line
Mylohyoid line
Mylohyoid groove
Submandibular fossa
Sublingual fossa
Ligaments
Fibrous capsule
Temperomandibular ligament
Sphenomandibular ligament
Stylomandibular ligament
Blood supply –
Branches of the superficial temporal and maxillary arteries
Nerve supply –
Branches of the mandibular part of the trigeminal nerve
What is the Temporomandibular joint (TMJ)?
Type
Synovial condylar joint
Articular surfaces
Temporal bone: - anterior part of the mandibular fossa
Head of the mandible.
Special feature
Articular disc
Muscles responsible for Movements of the TMJ
Temporalis muscle
Masseter muscle
Medial pterygoid muscle
Lateral pterygoid muscle
Platysma muscle
Suprahyoid muscles
Geniohyoid muscle
Mylohyoid muscle
Stylohyoid muscle
Digastric muscle
Infrahyoid muscle
Z
Movements:
Depression
Elevation
Protrusion
Retraction
Lateral movement
What are the function of your teeth?
to
Cut - incisors
Tear - canines
Grind food – molar and premolar
Teeth description
Primary and permanent dentitions have formed by
age 21
Primary – 20 deciduous teeth that erupt at intervals
between 6 and 24 months
Permanent – enlarge and develop causing the root
of deciduous teeth to be resorbed and fall out
between the ages of 6 and 12 years
All but the third molars have erupted by the end of adolescence
There are usually 32 permanent teeth
Tooth structure consists of 3 divisions
Crown
Root
Neck
And consists of 3 componants
Enamel
Dentin
Pulp cavity
Skull – depressed skull fracture: description, causes, symptoms, diagnosis, complications, treatment, differential diagnosis
Description
Nearly always the result of trauma
Part of the skull is pressed into the brain
Causes
Trauma
Symptoms
Recent trauma and head wound
Diagnosis
Plain film is almost never the primary imaging now
CT is the modality of choice. The fracture will be shown in detail along with any soft tissue injuries
Complications
Damage to underlying brain can cause haematomas, haemorrhages and CSF leaks
Treatment
Surgical management1
Differential diagnosis
Osteomas: description, causes, symptoms, diagnosis, complications, treatment, differential diagnosis
Description
Benign primary bone tumour
Causes
Can be associated with some syndromes but aetiology is unknown
Symptoms
May present as a slow growing mass
Diagnosis
Mainly occur in the paranasal sinuses, skull vault and nasal bone
Complications
Pain and disfigurement
Treatment
They are benign and are only removed if there are causing complications
Differential diagnosis
Any other cause of bony growth including Pagets
Diagnosis
Plain film
Appear as round lesions.
CT
Appear as round hyperdense lesions.
MRI
Appearances depend on the amount of bone marrow within the osteoma but on T1 normally give low signal
Skull fractures: description, causes, symptoms, diagnosis, complications, treatment, differential diagnosis
Description
Fracture of a skull vault bone. They are a marker of the severity of the injury. They can be classified as a base of skull fracture or skull vault fracture
Causes
Trauma
Symptoms
Depends on mechanism of injury
Diagnosis
Plain film is rarely used now.
CT is the first line investigation
CT is excellent at assessing the bony anatomy and allowing 3D reconstruction
Complications
Dependant on the underlying damage to the brain
Treatment
Conservative or surgical depending on severity
Paget’s disease: description, causes, symptoms, diagnosis, complications, treatment, differential diagnosis
Description
Common metabolic bone disorder which results in extensive bone remodelling
Causes
Unknown. More common as you age
Symptoms
Localised pain(
Increased bone size
Decreased range of motion
L
Diagnosis
Bloods can show elevated levels indicative of Paget’s
Complications
Pathological fractures and OA
Treatment
Medication to reduce bone growth and improve pain
Painkillers
Differential diagnosis
More rare bone disorders
Diagnosis in detail
Plain film and CT
Will see large, well defined lytic lesions in the skull. Sometimes sclerotic areas are also seen
Skull appears to fall over the facial bones
MRI
Bone has a speckled appearance with low signal intensity.
Nuclear medicine
Bone scintigraphy with Technicism is very sensitive but not specific
Skull metastases: description, causes, symptoms, diagnosis, complications, treatment, differential diagnosis
Description
Secondary cancer deposits in the bony skull
Causes0
Common in patients with skeletal metastatic disease
Cancers that most frequently metastasize are
Breast, lung, prostate, renal cell, multiple myeloma
Symptoms
Can cause pressure on the brain leading to seizures
In 90% of cases there will be bony metastases elsewhere
Diagnosis
Lytic lesions are the most common, but breast and prostate primary may result in sclerotic lesions.
Complications
May cause seizures or vision issues
Treatment
Many patients are at end of life so palliative care is given. Radiotherapy, chemotherapy and surgery can be used.
Differential diagnosis
Nonmalignant disease or Paget’s
What is Le Fort fractures?
Description
Fractures of the midface – which separate the midface from the skull base.
This includes fractures of the pterygoid plates and:
Nasal fossa
Inferior orbital rim
Zygomatic arch
Causes
trauma
Symptoms
Pain and visible facial injury
Multiple myeloma: description, causes, symptoms, diagnosis, complications, treatment, differential diagnosis
Description
Is a malignant bone neoplasm and the most common in adults
Causes
Unknown but more common in older age
Symptoms
Bone pain, anaemia, renal failure
Diagnosis – see across
Complications
Pathological fractures
Treatment
Incurable
Differential diagnosis
Metastases
Diagnosis
Radiography has a role in both diagnosis and management
It can diagnose, assess for complications and assess disease progression
Common appearances on plain film are lots of round lytic bone lesions and osteopaenia.
Plain film – a skeletal survey is often performed for diagnosis and monitoring.
However more than 40% bone destruction is needed for it to be seen so it has a high false negative rate
CT is more accurate – specificity of 90%, and sensitivity of 70%. Normally done as a low dose scan
MRI whole body is more sensitive but what are the possible issues with this?
PET-CT can help work out the disease distribution.1
Orbital blow out fractures: description, causes, symptoms, diagnosis, complications, treatment, differential diagnosis
Description
Describes a fracture of one of the walls of the orbit.
Causes
Typically, a fist or ball direct hit
Symptoms
Air around the eye (orbital emphysema)
Numbness in the area
The eye may be slightly displaced.
Diagnosis
Plain film is not recommended due to poor sensitivity
CT is the most used modality. Does not require contrast. CT can assess the fracture and the presence of bleeding.
Complications
Damage to the eye
Treatment
Generally now conservative management
Surgery if it’s a significant injury with risk of long term vision problems
Dental abscess: description, causes, symptoms, diagnosis, complications, treatment.
description: Acute infection of the periapical tissue around the tooth root
causes: Damaged tooth enamel allowing bacteria into the tooth
symptoms: Pain and swelling.
Infection symptoms
diagnosis: In the early stage (up to the first 10 days) there may be no imaging findings
OPG / CT may show a lucency at the tooth root
complications: Can result in loss of the tooth
Infection can spread to the neck / brain
treatment: Antibiotics
Mandible fracture: description, causes, symptoms, diagnosis, complications, treatment, differential diagnosis
description: One of the most common facial fractures (60-70%).
causes: Trauma, commonly road traffic collisions
symptoms: Patient may be unable to close or open their mouth. Pain.
diagnosis: Facial bones and OPG’s are common imaging methods, although CT is becoming more common as a first line imaging method.
MRI is the best imaging method for assessing the soft tissue damage.
complications:
treatment: Conservative
If the mandible is displaced the patient may need surgery with / without fixation
differential diagnosis