Skull, meninges and ventricular system

Question 1

What bones make up the calvarium?

Answer 1

Frontal
Parietal x 2
Occipital

Question 2

What is the pterion?

Answer 2

Joining point of temporal bone, frontal bone, parietal bone and sphenoid bone

Question 3

Why is the pterion clinically important?

Answer 3

Middle meningeal artery lies just deep to the pterion.

Trauma can cause extradural haematoma.

Question 4

At what age do the fontanelles close?

Answer 4

Posterior fontanelle = approx. 3 months

Anterior fontanelle = approx. 18 months

Question 5

What are the boundaries of the 3 intracranial fossa?

Answer 5

Lesser wing of sphenoid forms lower border of anterior cranial fossa.
Pretrous ridge of temporal bone forms the lower border of middle cranial fossa.

Question 6

What are the 2 layers of the dura?

Answer 6

Periosteal and meningeal layer

Question 7

What shape does an extradural haematoma take on a CT scan?

Answer 7

Dome shape formed by tethered ends at point of sutures

Question 8

Damage to what vessels are likely to cause a subdural haematoma?

Answer 8

Bridging veins that run across the subdural space (from veins into sinuses)

Question 9

Damage to what vessels are likely to cause a subarachnoid haematoma?

Answer 9

Cerebral arteries

Question 10

What are the functions of the dural reflections?

Answer 10

Stabilise and support of CNS structures

Question 11

What are the key dural reflections?

Answer 11

Falx cerebri (separates 2 hemispheres) 
Tentorium cerebelli (separates cerebellum from occipital lobe) 
Diaphragm sellae (sits over pituitary gland)

Question 12

What is the tentorium notch?

Answer 12

Free edge of the tentorium cerebelli where the brainstem runs through.
Potential site of herniation.

Question 13

Where are the dural venous sinuses found?

Answer 13

Between the 2 layers of dura

Question 14

What are the features of dural sinuses?

Answer 14

Valveless (meaning infection can track through them)

Endothelial lined

Question 15

Where is the cavernous sinus?

Answer 15

Lateral to the body of the sphenoid bone and the pituitary fossa

Question 16

What vessels run through the cavernous sinus?

Answer 16

CN III, IV, Va/b, VI

Internal carotid artery

Question 17

At what point is CSF drawn into the venous blood?

Answer 17

Superior sagittal sinus

Question 18

What is the function of the ventricular system?

Answer 18

Production, transport and removal of CSF

Question 19

What are the main functions of CSF?

Answer 19

Protection
Buoyancy (prevents excessive pressure at base of brain)
Chemical stability

Question 20

Where within the ventricular system is CSF produced?

Answer 20

Choroid plexus (made up of ependymal cells)

Question 21

Where is the ventricular system embryologically derived from?

Answer 21

Lumen of the neural tube

Question 22

What connects the third ventricle to the lateral ventricles?

Answer 22

Foramen of Monro (interventricular foramen)

Question 23

What are the two protrusions of the third ventricle?

Answer 23

Supra-optic recess (located above optic chiasm) 
Infundibular recess (located above the optic stalk)

Question 24

How does CSF travel from the third to the fourth ventricle?

Answer 24

Via the cerebral aqueduct

Question 25

How does CSF travel from the fourth ventricle to the spinal cord?

Answer 25

Via the central spinal canal

Question 26

How does CSF travel from the fourth ventricle to the brain?

Answer 26

Via the subarachnoid cisterns and into the space between the arachnoid mater and the pia mater

Question 27

How does CSF drain into the dural venous sinuses?

Answer 27

Through arachnoid granulations (small projections of arachnoid mater into the dura mater)

Question 28

What is hydrocephalus?

Answer 28

Abnormal collection of CSF within the ventricles of the brain leading to raised intracranial pressure and cerebral atrophy.
Can be classified into communicating (non-obstructive) and non-communicating (obstructive) hydrocephalus

Question 29

What is communicative (non-obstructive) hydrocephalus?

Answer 29

Abnormal build up of CSF in the absence of obstruction in the ventricles.
Commonly caused by functional impairment of the arachnoid granulations (e.g. fibrosis of subarachnoid space due to haemorrhage)

Question 30

What is non-communicating (obstructive) hydrocephalus?

Answer 30

Abnormal collection of CSF due to obstruction in the ventricles (commonly the cerebral aqueduct)

Question 31

What is the carotid body?

Answer 31

Located in close proximity to the carotid bifurcation (where common carotids become the external and internal carotids)
Chemoreceptors that detect pO2, pCO2, pH and temperature and feedback to the medulla oblongata