Cerebral Circulation

Blood brain barrier

Protective, selective membrane of specialised capillaries. Maintains homeostasis (equilibrium of brain). Protects the brain against fluctuations in ion concentrations

What arteries supply the brain?

Internal carotid arteries and vertebral arteries

What is the circle of willlis?

A anastomosis (connection) between the internal carotid and vertebral system

Branches of vertebral arteries? MPAPM

Meningeal, posterior spinal, anterior spinal, posterior inferior cerebellar, medullary

What’s the point of the circle of Willis?

Formed by an anastomosis (connection) between internal carotid artery and vertebral artery.

Adapted to prevent interruptions to blood flow even if one becomes blocked.

From this circle anterior, middle and post cerebral carotid artery travel to all parts of brain

What is the optic chiasm?

Where the optic nerve cross

What’s the choroid plexus? What arterial branch supply it?

A structure that produces cerebral spinal fluid. Choroidal branches supply it.

What branches supply the brainstem?

Branches from the basilar artery

What supplies cortical grey matter?

Cortical branches supply to the surface of the brain

What is the basal ganglia? What supply’s it?

A group of sub cortical nuclei in the brain that play a role in controlling movement, learning and emotional processing.

Supplied by the middle cerebral artery and posterior cerebral artery

what are lenticulostriate arteries?

Small arteries arising from the middle cerebral artery and supplying deep structures in the cerebrum (including basal ganglia and internal capsule)

No anastomoses which makes them susceptible to ischaemia (restriction in blood supply to tissues)

what does the anterior communicating artery do?

Cortical branches supply all of the medial surface of the cortex and a strip of cortex on the lateral surface.

Supplies the leg area of the motor and sensory cortex

Central branches supply parts of the basal ganglia and parts of the anterior visual pathway

What does middle cerebral artery do?

Largest branch of internal carotid artery.

Supplies large part of visual pathway, motor and sensory cortex and speech areas on the dominant hemisphere.

What does posterior cerebral artery do?

Supplies posterior lobe and part of temporal lobe, posterior part of visual pathway.

Central branches supply large proportion of thalamus

What is venous drainage?

Blood drains from deep in the brain substance into superficial veins which drain into large venous sinuses in the Dura mater.

Venous sinuses drain into the internal jugular vein.

The cavernous sinus receives blood from the anterior part of the base of the brain.

What’s cerebrovascular disease?

Any disease affecting an artery within the brain or supplying blood to the brain

Most common is atherosclerosis

What’s atherosclerosis?

Plaques (fatty deposits) form, narrowing the arteries. Defect or weakness in a blood vessel can cause an aneurysm (ballooning of artery)

What’s an aneurysm?

Ballooning of blood vessel from a weakness in the walls.

What’s a stroke?

Blood supply to part of the brain is blocked

What’s thrombosis?

Blood clot that forms in an artery

What’s an embolism?

A fragment of material or various other substances travelling in the blood stream

What can cause a blockage?

Thrombosis, embolism, atherosclerosis

How do they fix an aneurysm?

Coiling platinum wire in the aneurysm via a micro catheter.

Infarction?

Tissue death

Cerebrovascular disease risk factors that are modifiable?

Smoking, diabetes, hypertension, atrial fibrillation, carotid stenosis, hyperlipidemia

Cerebrovascular disease risk factors non modifiable?

Age, sex, race ethnicity, family history

Cerebral ischemia?

Irreversible brain damage occurs with death of nervous tissue after cessation of cerebral blood flow.

Occlusion of anterior communicating artery causes

Contralateral hemiparesis, sensory loss involving mainly leg and foot, personality changes

Occlusion of middle cerebral artery leads to

Contralateral hemiparesis and sensory loss involving face and arm, aphasia (if left cerebral cortex is affected), homonymous hemianopia.

most common artery affected in stroke

Occlusion of posterior cerebral artery leads to

Homonyous hemianopia, visual agnosia, impairment of memory

Signs and symptoms of cerebrovascular disease

Alteration in consciousness, headache, aphasia, facial weakness/assymetry, incoordination, weakness, paralysis, sensory loss of limbs, ataxia, visual loss

What is magnetic resonance imaging good for?

Useful for diagnosis of stroke because it can detect ischemic strokes (blood clot blocks vessel) within minutes of their onset.

Images of brain are superior in quality to computerised tomography (CT)

What is computerised tomography good for?

Type of X-ray used to detect haemorrhagic stroke (blood vessel in brain ruptures and bleeds)

CT good for this as they can easily and quickly detect bleeding inside the brain

Can also reveal ischemic stroke (blood clot block vessel) but only 6-12 hours after onset

Stroke treatments

Aspirin 160 to 300mg given asap and daily for suspected acute ischaemic stroke

Thrombectomy - endovascular thombectomy is removal of thrombus (blood clot). Catheter goes in artery