Skull and facial bones Flashcards
Frontal bone, what is it classed as and what does it articulates with?
Classified as a FLAT bone
Forms the front of the Cranium above the orbits
Articulates with: Maxillae, Zygomatic, Nasal, Lacrimal, Ethmoid and Sphenoid.
Parietal bone, what is it classed as and what does it articulate with?
Classified as IRREGULAR bones
Situated one either side of the midline
They form a large part of the roof and sides of the cranium
Articulates with the sphenoid and temporal bones
Each parietal bone has an internal and external surface
Each parietal bone have 4 boarders and 4 angles
Parietal – latin for wall
Temporal bone, what is it classed as and what does it articulate with?
What 3 parts does it develop from?
Temporal bone
Classified ad irregular bones
They form the sides and part of the base of skull
Each temporal bone develops from 3 separate parts
Squamous, Tympanic, Petromastoid.
Articulates with: head of the mandible, parietal bone, occipital bone, zygomatic bone and sphenoid bone.
Sphenoid bone, what is it classed as and what does it articulate with?
Classified as an irregular bone in the shape of a butterfly
Forms part of the base of skull
It lies between the frontal, temporal and occipital bones
Articulates with the Vomer, Ethmoid, occipital, frontal, zygomatic and palatine bones.
Ethmoid bone, what is it classed as and what does it articulate with?
Classified as an irregular bone
Occupying the superior part of the nasal cavity
It lies between the orbits & anterior to the sphenoid
Articulates with the vomer, maxillae, frontal, palatine, lacrimal & sphenoid bones.
Occipital bone, what is it classed as and what does it articulate with?
What areas is it divided into?
Classified as a flat bone forming the posterior part of the base of skull
Articulates, occipital condyles with the 1st cervical vertebra to form the atlanto-occipital joint
It can be divided into 3 areas
Squamous part
Basilar part
Lateral (condylar) part
What are the radiographic lines for imaging the skull?
OML- located between the outer canthus and the EAM.
IOML – formed by connecting the middle of the infraorbital margin to the EAM.
IPL – a line connecting either the pupils or the outer canthi of the patients eyes.
The IPL must be exactly perpendicular to the IR in a TRUE LATERAL position.
EAM – other wise known as the ear canal which is a passage comprised of bone and skin leading to the eardrum.
RADIOGRAPHIC LANDMARKS for skull imaging
TEA- Top of Ear Attachment
Auricle- External portion of the ear
Glabella- Area on the frontal bone above the nasion between the eyebrows.
Nasion- Nose
Canthus- Either corner of the eye where the upper and lower eyelids meet.
Acanthion- Midline point at the junction of the upper lip and the nasal septum
Gonion- The lowest posterior and most outward point of the angle of the mandible
Symphysis Menti- chin
External Occipital Protuberance- the bump you can feel on the back of your head
Vertex- top of your head
Mastoid Process- a bit right behind your ear
What do vessels look like on skull imaging?
Skull images will show the course of any vessels which indent the inner table, these indentations will branch and taper.
Unlike a skull fracture which will not branch and taper.
How do you know if there is a base of skull fracture and CT is not working, what imaging would we do and what would image look like?
When there is a base of skull fracture, usually blood or cerebrospinal fluid (CSF) will leak into the paranasal sinuses.
With the patient in the supine position and performing a lateral skull image you will see air/fluid in the Sphenoid sinus.
If the patient also has a facial injury, you will also see air/fluid in the other paranasal sinuses.
DEPRESSED FRACTURE
What injury would cause this?
Displaced or depressed skull fractures may be seen due to the overlapping of the bone causing an increased density.
The main causes of depressed skull fractures include labour and obstetric trauma in newborns and direct head trauma. e.g hit with a hammer
Base of skull fracture (Basilar skull fractures)
What injury would cause this?
Most basilar skull fractures occur in the setting of severe head traumas, such as those caused by motor vehicle accidents, motorcycle crashes, or pedestrian injuries.
Tangential views, what are they, what are they for?
FOREIGN BODY IMAGING OF THE SKULL
It is essential that ‘foreign body’ (FB), is specified on the request card to justify the request.
This is a specific radiograph performed with the beam angled at the correct alignment to the FB.
Theses views are known as:
Tangential views
Linear skull fracture information?
Most common skull #
MOI - Low-energy blunt trauma to wide surface area
Relatively insignificant unless it coincides with a suture, venous sinus groove or vascular channel where may lead to thrombosis, occlusion or haematoma
Greater than 3mm in width, runs in a straight line, widest at centre and narrower at tips = linear fracture
If line appears less than 2mm in width, uniform width throughout, and does not run in a straight line = suture
Basilar skull fracture info
Linear # at base of skull
Usually occur following a diffuse impact to the head
Often accompanied by a dural tear
75% accompanied by a temporal bone #
Associated symptoms;
-Anterior Cranial Fossa Fracture (70% of all BOS #)
CSF rhinorrhea – leakage of CSF extracranially into the paranasal sinuses and thus into the nasal cavity
-Raccoon Eyes
Basilar skull fracture symptoms?
Associated symptoms;
-Anterior Cranial Fossa Fracture (70% of all BOS #)
CSF rhinorrhea – leakage of CSF extracranially into the paranasal sinuses and thus into the nasal cavity
-Raccoon Eyes
Associated symptoms;
-Petrous Temporal Bone Fracture (5% of all BOS #)
-Battle Sign
-CSF otorrhea – leakage of CSF from the subarachnoid space into the middle ear cavity or mastoid air cells
-Otorrhagia – haemorrhage from the external auditory meatus to the external or middle ear
WHAT ABOUT MRI FOR TRAUMA? for skull imaging
NICE state not to use MRI as a first line investigation… why?
Relatively slow, expensive and less readily available when compared to CT
Difficulties associated with scanning the critically ill patient who may require life support
Contraindications to the modality, e.g. pacemakers, potential foreign bodies with certain traumatic injuries
Insensitive to acute haemorrhage and fracture when compared to CT
What is Cholesteatoma?
abnormal collection of skin cells deep inside the ear
Can be caused by a birth defect, most commonly caused by repeated middle ear infection.
Often develops as a cyst or sac that then sheds layers of old skin.
Treatment: once found is usually surgery and involves a mastoidectomy which removes the disease form the bone and tympanoplasty to repair the eardrum.
Symptoms: constant sound in your ear known as tinnitus, vertigo, recurrent ear infections, pain, fluid leaking from the ear which contains bad smell, sometimes a weakness in the side of the face.
Another example here within the ossicular chain in the inner ear – disrupted the 3 small bones of your ear Malleus, Incus and Stapes
Imaging for the ear, why would we do it?
Imaging an be used to investigate;
-Hearing loss
-Cholesteatoma
-Tumours (e.g. Schwannomas)
-Bony changes in the ear canal
Conductive Hearing Loss (CHL) CT or MRI and what is it?
CHL - Disruption of the transmission of sound waves from the outside environment to the cochlea. Common pathologies that produce CHL include otitis, TM rupture, cholesteatoma and trauma.
CT scan of the temporal bones
Provides a superior evaluation of the bony sound conduction pathway
Sensorineural Hearing Loss (SNHL) CT or MRI and what is it?
SNHL – Dysfunction of the cochlea or disruption of neural impulses in the central auditory pathway. This can be seen with internal auditory canal (IAC) tumours, labyrinthitis and CNS pathology.
SNHL
MRI
Better assesses the vestibulocochlear nerve and CNS
MRI becoming more utilised due to lack of ionising radiation dose
What is the the otic capsule
The otic capsule refers to the dense osseous labyrinth of the inner ear that surrounds the cochlea, the vestibule and the semi-circular canals. It is surrounded by the mastoid part of the temporal bone.
Note slide
Skull consists of;
Inner table
Outer table
Diploe (space in between)
The thicknesses of outer and inner table are 1.5 mm and 0.5 mm, respectively.
Note slide
Skull consists of;
Inner table
Outer table
Diploe (space in between)
The thicknesses of outer and inner table are 1.5 mm and 0.5 mm, respectively.
OSTEOMYELITIS of the skull appearance?
Osteomyelitis
OF skull shows irregularity and erosion of right side of skull with associated ST swelling
CECT shows mild heterogenous enhancement of the ST in right frontal region.
When viewed on a bone window, clearly demonstrates irregular erosion of the inner and outer table of skull.
Multiple Myeloma appearance on x-ray?
Generalised osteopaenia and/or lytic bone deposits on plain film radiography
Sharply defined, small lytic areas (average size 20 mm) of bone destruction with no reactive bone formation
The pattern of destruction may be geographic, moth eaten or permeated. Pathological fractures are common
USE OF ULTRASOUND FOR IMAGING THE SKULL
Limited usage
Can be used prenatally for measurements of skull in the developing foetus
Can scan through the open fontanelles in infants up to18 months to view the brain and ventricles
Likewise can be used in adults where skull has been opened up
USE OF RNI FOR IMAGING THE SKULL
Use of Bone Scintigraphy
Can be used;
In the diagnosis of Osteomyelitis that may or may not show on plain radiography
Evaluation of disease extent with a widespread pathology such as Paget’s Disease
To localise avascular necrosis
To view areas of increased focal activity when metastatic spread is suspected
A combination of focal hyperperfusion, focal hyperemia, and focally increased bone uptake is virtually diagnostic for osteomyelitis in patients with nonviolated bone. Bone scintigraphy is also useful for evaluating disease extent in Paget disease and for localizing avascular necrosis in patients with negative radiographs.
