Vasclature of the head, face & brain Flashcards
Label the attached image which shows the vasculature of the scalp.
There are two veins of the scalp which present a particular risk for infection from superior cranium to intercranial structures. What are these two veins called?
Supratrochlea v. & Supraorbital v. are valveless veins that drain into the cavernous sinus. This makes them a particular risk for infection from superior cranium to inter.
Label the attached diagram of a superior view of the cranium.
Label the attached diagram of a lateral view of the cranium.
What is the Pterion?
The Pterion is the region where the temporal, frontal, sphenoid and parietal bones join.
It is a point of weakness of the cranium. On the interior surface of the pterion the middle meningeal vessels lie.
What artery is likely to be damaged / ruptured in a Pterion fracture?
Middle meningeal a.
This would cause an extradural haematoma; these are expansile and thus a hole in the Pterion region of the skull would be required to minimise compression of surrounding cerebral tissue and to clamp the bleed.
Identify the structures in this posterior view of the cranium
Identify the structures in this internal view of the floor of the cranium.
Fractures in what bone/s will cause CSF to leak through the nose?
Fractures to the frontal bone can see CSF leak through the cribriform plate > into the nasal cavity.
Fractures to the sphenoid bone can see CSF leak into the sphenoid sinus > into the nasal cavity.
Fractures in what bone/s may cause CSF to leak into the middle ear / out of the auditory canal in the case of a perforated ear drum?
Fractures to the temporal bone can lead to leaking of CSF into the middle ear / out of the ear.
What are the thickest areas of the cranium?
- Mastoid process,
- External occipital protuberance,
- Glabella (frontal bone)
What are the layers of the cranium?
Layer 1: Outer table / Lamina externa (thick)
Layer 2: Cancellous bone / Diploe (almost absent in region covered by temporalis muscle - prone to fracture).
Layer 3: Inner table / Lamina interna (thinner)
The most common areas of skull fractures include:
The cranium vault: frontal, temporal and parietal bones.
The floor of the cranium: the anterior cranial fossa.
Terminology for describing skull fractures includes:
1. Location
2. # Fracture lines
3. Displacement
4. Continuity to exterior
Provide the possible terms for each
Location = vault of skull or base of skull.
of fractures = Linear or comminuted.
Displacement = Depressed or non-displaced.
Continuity to exterior = Simple (closed) or Compound (open).
Linear cranial fractures are the most common type of cranial fractures what is the most likely mechanism of injury?
Blunt forced trauma over a relatively wide area of the skull (ie along a flat surface).
How does a linear cranial fracture appear in imaging?
Thin line, no depression, may or may not be associated with a suture line.
Significant if the fracture runs through a vascular channel, air sinus, CN foramina or a suture line.
What is a diastatic cranial fracture?
A linear cranial fracture observed in infants with unclosed cranial bones.
How does a depressed cranial fracture appear in imaging?
Fracture to cranium with effected region compressed in toward the brain tissue.
Can be comminuted as the mechanism of injury are the same.
What is the most common mechanism of injury for a depressed fracture?
Blunt forced trauma over a small surface area.
What is the most common mechanism of injury for a depressed fracture?
Blunt forced trauma over a small surface area.
Why are depressed cranial fractures associated with increased risk of brain injury.
Fracture may damage tissue directly causing contusion / laceration and subsequent seizures and neurological deficits.
In imaging what features allow for differentiation between a fracture and a suture line?
- Width: fractures are greater than 3mm / sutures are less than 2mm wide.
- Diameter throughout: fractures are wider in the centre and narrower at the ends of the fracture / sutures are the same diameter throughout.
- Opacification: Fractures are typically darker than sutures.
- Location: Fractures are common over the parietal and temporal bones / Sutures are located at specific anatomical sites.
- Direction: Fractures commonly run in straight lines / sutures do not run in straight lines.
What is a Pheumocephalus?
Air can enter into the cranial cavity.
What is a Subcutaneous emphysema?
Air collects in the subcutaneous tissue.
Signs of compound cranial fractures includes:
- Presence of gas (air) in the cranial cavity.
- Presence of a foreign body in the cranial cavity.
- CSF rhinorrhoea (CSF leaking through nasal cavity).
- CSF otorhoea (CSF leaking through the middle ear) - via eustachian tube or external ear canal in cases of perforated ear drum).
Epistaxis means?
Bleeding from the nose. This can be a sign of a compound cranial fracture ONLY if it is mixed with CSF.
What nerve runs between the Posterior Cerebral a. and the Superior Cerebella a. near to the level / parallel to the Posterior communicating a.?
The Oculomotor n. CN III
Why do infarctions / lesions to the occipital pole and local area result in homonymous hemianopia with macula sparing?
The macular representing regions of the occipital cortex (1-4 in the attached image) receives dual blood supply therefore the macular region is spared.
