APO9: blood supply to the intracranial tissues

Question 1

state 2 diseases caused by lack of BBB

Answer 1

1.Multiple sclerosis:
Multiple sclerosis is considered to be an autoimmune and neurodegenerative disorder in which the immune system attacks the myelin that protects and electrically insulates the neurons of the central and peripheral nervous systems.

Normally, a nervous system would be inaccessible to the white blood cells due to the blood–brain barrier.

However, magnetic resonance imaging has shown that when a person is undergoing an MS “attack,” the blood–brain barrier has become more permeable in a section of the brain or spinal cord, allowing white blood cells called T lymphocytes to cross over and attack the myelin.

One consideration is multiple sclerosis may be a disease of the blood–brain barrier

2.Treatment of meningitis

Meningitis is most commonly caused by infections with various pathogens, examples of which are Streptococcus pneumoniae and Haemophilus influenzae.

When the meninges are inflamed, the blood-brain barrier may be disrupted.

This disruption may increase the penetration of various substances (including either toxins or antibiotics) into the brain.

These Antibiotics especially consider ones used to treat meningitis may aggravate the inflammatory response of the central nervous system by releasing neurotoxins from the cell walls of bacteria-like lipopolysaccharide (LPS)

This inflammation can cause swelling–> ICP–> reduced cerebral blood flow–> supra-tentorial herniation

so use different types of antibiotics like third- fourth gen cephalosporins

Question 2

What are the requirements of brain statistically of blood flow when rest and how maintained

Answer 2

Brain 2.5% body weight but 20% CO
So at rest receives 1.1L/min of blood
This is maintained by autoregulation of cerebral blood vessels

Question 3

Describe the pathway of the vertebral arteries into the cranial cavity

Answer 3

1st branch from subclavian artery

ascends thorugh tranvserse foramen of C1-C6

asencds with the vertebral vein and post-ganglionic sympathetic fibres

then wraps around the articular facet of C1

it then pierces the dura and arachnoid mater to enter the sub-arachnoid space as it passes through the foramen magnum

Question 4

Describe the pathway of the internal carotid artery to point in cranial cavity

Answer 4

· the internal carotid artery arises from the bifurcation of the common carotid artery at C4 level or superior border of the thyroid cartilage

• at its origin it is demarcated by a dilation known as the carorid sinus which contains baroreceptors
• at its bifurcation it is angled posteriorly

· the internal carotid artery then moves superiorly through the carotid sheath and enters the brain via the carotid canal in the temporal bone

• the carotid canal is located within the petrous part of the temporal bone anterior to the jugular foramen

· within the cranial cavity the internal carotid artery passes anteriorly through the cavernous sinus

· distal to the cavernous sinus the internal carotid artery then enters the cranial cavity proper at the anterior clinoid process of the body of sphenoid in the middle cranial fossa

the internal carotid artery then pierces through the dura and arachnoid mater to be in the sub-arachnoid space where it bifurcates to form the middle and anterior cerebral artery

Question 5

State major branches of ICA and where does this occur

Answer 5

distal to the cavernous sinus towards the base of the brain the internal carotid artery gives rise to the: anterior cerebral artery, posterior communicating artery, ophthalmic artery and the anterior choroidal artery

· the internal carotid artery then continues as the middle cerebral artery

Question 6

State major branches of ICA and where does this occur

Answer 6

as it is travelling through the carotid canal and petrous part of temporal bone it gives smaller branches

in petrous TB give branch to middle ear

then as enters cavernous sinus gives branch to supply dura mater of cavernous sinus, pituitary gland

further on give branch to trigeminal ganglion

then medial to the anterior clinoid process of sphenoid bone gives opthalmic artery branch andjust before bifurcates it gives the posterior communicating artery which anastamoses with the posterior cerebral artery

in the sub-arachnoid space where it bifurcates to form the middle and anterior cerebral artery

Question 7

State the branches of vertebral and basal arteries and where they occur

Answer 7

Once the vertebral arteries have ascended to the brainstem

the first branch they give at the medulla is the posterior inferior cerebellar arteries

the posterior inferior cerebellar arteries each will give rise to the posterior spinal arteries

then at more rostral end of the medulla the two vertebral arteries give rise to branches which fuse to form the single anterior spinal artery

then at the pontomedullary junction the 2 vertebral arteries fuse to give the basilar artery

the basilar artery as it ascends will give the two anterior inferior cerebellar arteries and then more superiorly the labyrinthine artery

then further up will give several pontine branches either side

then at the mid-brain will give the superior cerebellar arteries

then past-mid-brain immediately superior to posterior cerebellar arteries it terminates by giving the posterior cerebral arteries

Question 8

Define ischaemia

Answer 8

ischaemia is where there is decrease oxygen supply to tissues or where tissues have increased oxygen demand

where body oxygen supply not enough to need therefore