Bloody Supply To The CNS

Question 1

Describe the blood supply to the brain and label diagram

Answer 1

Front = internal carotid arteries and back = veterbral arteries

The external carotid artery supplies the face and the internal carotid makes its way up to the skull to supply cerebral hemisphere, the subclavian branches into transverse foramina and foramen magnum.

The veterbral artery gives rise to the circle of Willis.

2 veterbral arteries > Basilar artery > posterior cerebral artery > posterior communicating artery > middle cerebral artery > internal carotid > anterior cerebral artery > anterior communicating artery

Question 2

Describe the venous drainage of the brain

Answer 2

Cerebral veins > venous sinuses > dura matar > internal jugular vein.

Running along the top = saggital sinus between two folds of dura matar = CSF drains into venous system

Question 3

What are the 4 problems with a deficit in blood supply to the brain?

Answer 3

1. Stroke - cerebrovascular accident (CVA) - rapidly developing focal disturbances of brain function of presumed vascular origin and 24> duration
2. transient ischaemic attack (TIA) - rapidly developing focal disturbance of brain function of presumed vascular origin that resolves itself within 24h
3. Infarction - degenerative changes that occur in tissue following occlusion of an artery (area of dead tissue loss of blood supply)
4. Cerebral ischaemia - lack of sufficient blood supply to nervous tissue resulting in permanent damage if blood flow is not resolved quickly

Question 4

What are the 2 reasons for occlusions?

Answer 4

Thrombosis - formation of blood clot

Embolism - plugging of small vessel by material carried from larger vessel

Question 5

Describe the effects of blockage in each perfusion fields

Answer 5

1. Anterior cerebral artery - paralysis of controlateral leg > arm, disturbance of intellect, executive function, loss of appropriate social behaviour
2. Middle cerebral artery - classic stroke, controlateral arm > leg, hemisensory defect, hemianopia, aphasia,
3. Posterior cerebral artery - visual defects - homogenous hemianopia, visual agnosia.

Question 6

What are lacunar infarcts

Answer 6

Small strokes that have happened during someone’s life, lacun = small cavity, appear in deep structure as a result of small vessel occlusion, deficit is dependent on anatomical location, hypertension.

Question 7

Describe the effects of a haemorrhaging stroke.

Answer 7

Extradural - due to trauma has immediate effect
Subdural - due to trauma has delayed effect
Subarachnoid - ruptured aneurysm
Intracebral - spontaneous hypertension

Question 8

Describe the differences in the dura and veterbrae

Answer 8

The veterbral coloumn has single layer, with fat between bone.
Skull is double layer - periosteal and meningeal
A fold in dura expands to form falx cerebri
The falx cerebri peels to form superior saggital sinus
Within saggital sinus is arachnoid granulation