Skull, Meninges, Ventricular System & CSF Flashcards
How many bones make up the skull?
22
How is the skull split up?
Neurocranium (protecting brain)
Visceracranium (protecting face)
What are the different sutures of the brain?
Coronal
Sagittal
Lambdoid
What are the structures found in an infants skull that are no longer present in an adults?
Anterior fontanelle - closes at 18 mnths
Posterior fontanelle - closes at 3 months
Mastoid + sphenoidal fontanelle
What is the pterion and why is this clinically important?
Weak spot where the parietal bone, squamous part of temporal bone and sphenoid join - middle meningeal artery lines underneath it so if it become damaged, the artery is at risk
What bones make up the neurocranium?
Ethmoid Frontal Occipital 2 x parietal Sphenoid 2 x temporal
What bones make up the visceracranium?
2 of each: Inferior nasal concha Lacrimal bones Mandible Maxilla Nasal bones Palatine bones Vomer Zygomatic bones
What is the difference in adult and neonatal skull appearances?
Neonatal skulls have a bigger calvarium and sutures are not fused in contrast to adult skulls
What can fontanelles be used for?
US’s
What is the ossification centre?
Where bones start to ossify so you can see radiations coming from these points e.g. in the skull
What are the features of the flat skull bone?
Bone between scalp/pericardium and dura
Bone has an external and internal table with diploe in between
What bone down the internal acoustic meatus sit in?
Petrous part of temporal bone
What are the 3 cranial fossa’s?
- Anterior
- Middle
- Posterior
What comes out of the inferior orbital fissure?
CNVb comes out of this hole in the inferior part of the orbit bone
What are the 3 meningeal layers (external to internal)?
- Dura (periosteal and meningeal layer)
- Arachnoid mater
- Pia mater
What are the cranial meninges continuous with?
Spinal meninges through the foramen magnum
Damage to what vessel would cause a extradural haematoma?
Middle meningeal artery
What would a extradural haematoma look like?
Lens like shape due to sutures preventing further spread
How do you deal with brain bleeds?
Relieve pressure by draining it out
Damage to what vessel would cause a subdural haematoma?
Bridging veins
What would a subdural haematoma look like?
It would span the whole hemisphere on one side
Damage to what vessel would cause a subarachnoid haemorrhage?
Cerebral arteries for e.g. due to an aneurysm
What way could you detect a subarachnoid haemorrhage without scanning the brain?
Blood cells would be seen in a lumbar puncture sample as the subarachnoid space is where CSF is present
What are dural reflections?
The meningeal layer of the dura forms several double-layered folds which project inwards, separating parts of the brain that help to stabilise and support CNS structures
What dural reflections are present in the brain?
Falx cerebri (separates hemispheres)
Tentorium cerebelli (over cerebellum)
Falx cerebelli
Diaphragm sellae
What is the tentorial notch? Why is this clinically relevant?
Free edge of the tentorium cerebelli so this is a potential site of herniation of anything above the notch when there is raised ICP
What are dural venous sinuses?
Valveless sinuses that are endothelial lined running between the 2 layers of dura mater that receive venous drainage from the cerebral cortex that goes through them ending up in the IJVs
What are the venous sinuses?
Superior sagittal Inferior sagittal Straight Transverse Sigmoid Cavernous
Where is the confluence of sinuses located?
connecting point of the superior sagittal, straight, and occipital sinus found deep to the occipital protuberance of the skull
How can a boil on the forehead cause cavernous sinus thrombosis?
Infection can track back into the intracranial venous sinuses as the sinuses are valveless getting into the cavernous sinus and causing thrombosis as a blood clot forms to try and prevent infection spread - this can damage many CNs via compression and block important vessels
Where is the cavernous sinus?
Lies laterally to the body of the sphenoid bone and sinus and pituitary fossa (pituitary gland and diaphragm sellae covering it) - also close to optic chiasm
What is contained within the cavernous sinuses?
CNs III, IV, Va, Vb and VI
ICA
Where is cerebrospinal fluid (CSF) produced? What does it then do?
Constantly produced in the ventricular system by choroid plexus (mostly lateral ventricles) and then circulates around the CNS to protect, nourish and cushion the brain giving it buoyancy
What route does cerebrospinal fluid (CSF) take?
- From lateral ventricle through IV foramen to 3rd ventricle
- Goes through cerebral aqueduct to get into 4th ventricle
- Goes through lateral (x2) and median (most) apertures to get into subarachnoid space
- Can then circulate around brain or go down central canal of spinal cord
Where is the cerebral aqueduct?
Between the cerebellum and brainstem to the 4th ventricle
What will the choroid plexus look like?
Fluffy appearance
4th ventricle is continuous with _______.
Central canal of spinal cord
Where is cerebrospinal fluid (CSF) reabsorbed?
Into dural venous sinuses and then into venous blood through superior sagittal sinus arachnoid villi/granulations
What problems can go wrong with the ventricular system?
Blockage can cause a CSF build-up resulting in enlargement of the ventricles causing hydrocephalus - raised ICP, squashing structures and potentially causing herniation
What are the common places for the ventricular system to get blocked?
Cerebral aqueduct will disrupt flow
Arachnoid space will disrupt reabsorption
What effect of hydrocephalus would you see in an infant but not in an adult?
Hydrocephaly where the head is enlarged as there bones and sutures are not fused together properly
How do you fix a ventricular system blockage?
Drain the built up CSF by putting a shunt in
