BLOOD SUPPLY OF BRAIN

BYPROF. DR. ANSARI

(BDS-II SEMESTER RAKCODS)

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A 78 year old man was admitted from a residential home having collapsed

suddenly. He was known to have been hypertensive and had been a smoker.

• On examination he had dysphagia, right sided hemiplegia, brisk right sided reflexes and a right up going plantar response. A clinical diagnosis of a cerebral ischemia was made.

• CT of the brain was performed after 12 hours of admission &shown below:-

Areas of infarction

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Circle of Willis At the base of brain

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The objectives are

• Formation of circle of Willis/ Circulus Arteriosus

• Areas of cerebrum and cerebellum supplied by each branch from vertebrobasilar arterial arcade.

• Venous drainage from cerebrum and cerebellum.

• Applied anatomy of vertebrobasilar insufficiency.

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The circle of Willis/Circulus arteriosus

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The circulus arteriosus is formed• Between branches of internal carotid arteries and

vertebral arteries.• It is placed in the cisterna interpeduncularis, at the

base of the brain.• The internal carotid arteries, right and left enters

the cranium passing through the internal carotid foramina.

• The two vertebral arteries enter the cranium through the foramen magnum.

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The right sided arteries communicate with the left sided

• By means of one anterior and two posterior communicating arteries.

• The members of circle are:-• (a) anterior cerebral• (b) anterior communicating • © Posterior communicating &• (d) posterior cerebral• There are two types of branches arising from the

circle.

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The cortical branches

• Are superficial branches visible on the surfaces of the brain and they supply the cortical gray matter.

• The deep branches are central branches that perforates the substance of brain and supply the deep nuclei.

• These deep branches are end arteries, they never form anatomosis with their neighbours.

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The brain needs glucose and oxygen

• For its proper functioning. The astrocytes form the blood brain barrier along with the endothelium of the capillaries.

• Brain cannot sustain anoxia for more than few minutes, there will be permanent damage to the neurons, if the blood supply is not restored after few minutes & brain death will occur.

• The medial surface of the cerebral hemisphere is supplied by anterior cerebral artery, the branches cross over the superior border and supply a fingers breadth area on the superiolateral surface of hemisphere.

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ACA

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Obstruction of anterior cerebral artery leads to paraplegia

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Personality dysfunction occur due to infarction of both anterior cerebral arteries • If both anterior cerebral arteries arise from one

stem major disturbances occur with infarction occurring at the medial aspects of both cerebral hemispheres resulting in aphasia, paraplegia,

incontinence and frontal lobe/personality dysfunction.

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Occlusion of one anterior cerebral artery distal to anterior communicating artery results in

– Contra lateral weakness and sensory loss, affecting mainly distal contra lateral leg (foot/leg more affected than thigh).

– Mild or no involvement of upper extremity.– Head and eyes may be deviated toward side of lesion

acutely.– Urinary incontinence with contra lateral grasp reflex and

paratonic rigidity may be present.– May produce transcortical motor aphasia if left side is

affected.– Disturbances in gait and stance = gait apraxia.

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MIDDLE CEREBRAL ARTERY (MCA):

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• Sensory and motor deficits on contralateral face and arm > leg

• Head and eyes deviated toward side of infarct• With left-side lesion (dominant hemisphere)—

global aphasia initially, then turns into Broca's aphasia (motor speech disorder)

• Right side lesion (nondominant hemisphere)—deficits on spatial perception, hemi-neglect, constructional apraxia, dressing apraxia

• Muscle tone usually decreased initially and gradually increases over days or weeks to spasticity

• Transient loss of consciousness is uncommon

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Wallenberg's syndrome also known as lateral medullary syndrome, PICA syndrome, and vertebral artery syndrome.

– Ipsilateral side • Horner's syndrome (ptosis, anhydrosis, and miosis)• decrease in pain and temperature sensation on the

ipsilateral face• cerebellar signs such as ataxia on ipsilateral extremities

(patient falls to side of lesion)– Contralateral side • Decreased pain and temperature on contralateral body

– Dysphagia, dysarthria, hoarseness, paralysis of vocal cord– Vertigo; nausea and vomiting– Hiccups

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Medial Medullary Syndrome• Typical syndrome: – Ipsilateral hypoglossal palsy (with deviation toward the

side of the lesion)

– Contralateral hemiparesis.

– Contralateral lemniscal sensory loss

– (proprioception and position sense)

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Occlusion of Posterior cerebral artery• Visual field cuts (including cortical blindness when bilateral)• May have prosopagnosia (can't read faces)• palinopsia (abnormal recurring visual imagery)• alexia (can't read)• transcortical sensory aphasia (loss of power to comprehend

written or spoken words; patient can repeat)• Structures supplied by the interpeduncular branches of the

PCA include the oculomotor cranial nerve (CN 3) and trochlear (CN 4) nuclei and nerves

• Clinical syndromes caused by the occlusion of these branches include oculomotor palsy with contralateral hemiplegia = Weber's syndrome and palsies of vertical gaze (trochlear nerve palsy)

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The superiolateral surface of cerebral hemisphere is supplied by MCA

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The posterior cerebral artery

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The cerebellum is supplied by three cerebellar arteries-AICA/PICA/SCA

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The central /straited branches

• These are central Branches /

that dips inside the substance of brain

&supply the deep Nuclei.

They arise fromCircle of Willis.

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• By apoplexy is meant the rupture of a blood-vessel with consequent extravasations of blood, either in or on the brain.

• It may occur in any portion of the brain, and either from the arteries of the base, or from the smaller arteries of the cortex.

• The former is the more frequent. The arteries that most often rupture are the branches of the middle cerebral which enter the anterior perforated space, especially its outer portion.

• One of the largest of these anterolateral arteries, as has already been mentioned, known as the lenticulostriate, has been called by Charcot the artery of cerebral hemorrhage

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HYPERTENSIVE HEMORRAGE IN THE BASAL GANGLIA & THALAMUS

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Berry aneurysm

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Large aneurysm at the cerebello-pontine angle

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Pontine hemorrhage

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Pontine hemorrhage• Patients with a large central hemorrhage present with a progressive

decrease in the level of consciousness rapidly leading to coma.• Bilateral bulbar muscle weakness, "pinpoint" pupils, hyperthermia,

and hyperventilation are common associated findings.• This presentation is seen most often in patients with uncontrolled

hypertension .• . Contralateral hyperhidrosis in the subacute or late phase after

pontine hemorrhage may be seen. • This is thought to be secondary to disruption of contralateral

inhibitory sweating pathway .• Up to one third of patients may develop a severe headache before

the onset of focal signs .• Vomiting may be seen in 20% of patients, and seizures (mostly flexor

spasms and not true convulsions) have been reported in 30% of patients

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The venous drainage of brain• Cerebral veins drain the surfaces of brain, they run

in the sulci and gyri and drains into near by dural venous sinuses.

• Deep cerebral veins drain in to the straight sinus.• The cerebellum is drained by cerebellar veins which

ends up into the near by dural venous sinuses.• All dural sinuses emerges from the internal jugular

foramen and comes out as internal jugular vein.

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Cavernous sinus

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The dangerous area of face

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Cavernous sinus thrombosis

• Clinical manifestations include dysfunction of cranial nerves III, IV, V, and VI, marked periorbital swelling, chemosis, fever, and visual loss.

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The dural venous sinuses

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