5. 2 Anatomy of Cerebral Blood Flow

Question 1

What is the course of the internal carotid arteries?

Answer 1

Bifurcation of common carotid arteries (C4) –> Within carotid sheath –> carotid canal –> pass anteriorly in the cavernous sinus

Question 2

What are the branches of the ICA

Answer 2

• Ophthalmic artery (orbit)
• Posterior communicating artery (anastomosis in circle of Willis)
• Anterior choroidal artery (structures in brain involved in motor control and vision)
• Anterior cerebral artery (runs in longitudinal fissure between cerebral hemispheres; connected by anterior communicating artery)
• Middle cerebral artery (runs laterally)

Question 3

What is the course of the vertebral arteries?

Answer 3

1st part of subclavian artery –> transverse foramen (C1-C6) –> foramen magnum

Question 4

What are the branches of the vertebral arteries?

Answer 4

• Meningeal branch (falx cerebelli)
• Anterior and posterior spinal arteries
• Posterior inferior cerebellar artery (PICA)
• Basilar artery (splits into posterior cerebral arteries)
• Anterior inferior cerebellar artery
• Superior cerebellar artery
• Pontine arteries

Question 5

The Circle of Willis is a circular blood vessel (around the _______________) formed by the anastomosis of the terminal branches of the vertebral and internal carotid arteries:
• Allows for compensatory flow if one of the arteries is blocked (e.g. atherosclerosis)
• Limited compensatory flow between the anterior and posterior arteries (due to the smaller diameter of the posterior arteries)

Answer 5

pituitary gland

Question 6

What are the components of the circle of willis?

Answer 6

• Anterior cerebral arteries
• Internal carotid arteries
• Posterior cerebral arteries
• Anterior communicating
• Posterior communicating

Question 7

Structures surrounding the pituitary gland: Circle of Willis surrounds the pituitary gland

• _______________________ lies inferior to the gland (route for transsphenoidal hypophysectomy –> avoids the vessels lying lateral to gland)
• Cavernous sinus (lined by dura mater) lies lateral to the gland (with ___________ passing through it –> ICA bifurcates after passing through the cavernous sinus)

Answer 7

Sphenoidal air sinus and the sella turcica (pituitary fossa);

ICA, CN III, IV, VI

Question 8

Where does the venous drainage of the brain occur?

Answer 8

cerebral veins, which empty into the dural venous sinuses (within the dura mater) then the IJV

Question 9

where does the superior cerebral veins drain to?

Answer 9

Superior surface to superior sagittal sinus

Question 10

where does the superficial middle cerebral vein drain to?

Answer 10

Lateral surface to cavernous or sphenopalatine sinuses

Question 11

Where does the inferior cerebral veins drain to?

Answer 11

Inferior surface to cavernous or transverse sinuses

Question 12

Where does the Superior anastomotic vein (of Trolard) drain to?

Answer 12

Superficial middle cerebral vein to superior sagittal sinus

Question 13

Where does the Inferior anastomotic vein (of Labbé) drain to?

Answer 13

Superficial middle cerebral vein to transverse sinus

Question 14

Where does the subependymal veins drain to?

Answer 14

Receive blood from medullary veins and carry it to the dural venous sinuses:
• Great cerebral vein (of Galen): to straight sinus

Question 15

Where does the Medullary veins drain?

Answer 15

Deep areas of brain to subependymal veins

Question 16

Where does superior sagittal sinus drain?

Answer 16

Runs towards back of head → confluence of sinuses (opening within the dura mater)

Question 17

Where does inferior sagittal sinus drain?

Answer 17

Runs towards back of head → straight sinus → confluence of sinuses (opening within the dura mater)

Question 18

Where does confluence sinuses drain?

Answer 18

Drains laterally via transverse sinus → sigmoid sinus → jugular foramen → IJV

Question 19

which part of the brain does the anterior cerebral artery supply?

Answer 19

thin 1cm outer lateral aspect of the lateral brain, wide circulation medially and a large part of the anterior cerebral cortex

Question 20

which part of the brain does the middle cerebral artery supply?

Answer 20

large part of lateral brain, small component of midline brain

Question 21

which part of the brain does the posterior cerebral artery supply?

Answer 21

posterior brain (occipital lobes and inferior temporal lobes)

Question 22

what is the clinical presentation of the anterior infarct of the brain?

Answer 22

• Contralateral hemiplegia: leg > arm, face (primary motor cortex)
• Abulia: disturbance of intellect, executive function, judgement (frontal lobes)
• Loss of appropriate social behaviour (disinhibition) (frontal lobes)

Question 23

what is the clinical presentation of the middle (classic) infarct of the brain?

Answer 23

• Contralateral hemiplegia: arm > leg (primary motor cortex)
• Contralateral hemisensory deficits (sensory cortex)
• Homonymous hemianopia (loss of half of visual field)
• Aphasia (left-sided lesions): disrupt speech (language centres)
o Receptive aphasia: cannot understand but can speak (but lack content/meaning) → Wernicke’s area affected
o Expressive aphasia: can understand but not express the correct words → Broca’s area affected
o Conduction aphasia: difficulty in repeating phrases (disconnection between Wernicke’s and Broca’s area

Question 24

what is the clinical presentation of the posterior infarct of the brain?

Answer 24

• Visual deficits (affecting occipital lobe and visual cortex):
o Homonymous hemianopia (loss of half of visual field on same side or both eyes)
o Visual agnosia: inability to recognise things based on vision (e.g. prosopagnosia: inability to recognise faces and people)

Question 25

Lacunar strokes/infarcts (LACI) are the most common type of ischaemic stroke resulting from the occlusion of small penetrating vessels supplying the deep structures of the brain: • Risk factors: ____________, advanced age, smoking, diabetes mellitus • _________________- within 3 – 4 hours, correction of underlying risk factors (prevention of recurrence), rehabilitation • Can be classified into one of five lacunar syndromes (presentation depends on the location of the lesion)

Answer 25

chronic hypertension; Treatment: tissue plasminogen activator (alteplase, streptokinase);

Question 26

[lacunar strokes] Pure motor stroke/ hemiparesis - location: Posterior limb of internal capsule, basilar pons, corona radiata - presentation: ???

Answer 26

Contralateral hemiplegia or hemiparesis (face, arm, leg): | • Dysarthria, dysphagia, transient sensory symptoms

Question 27

[lacunar stroke] Ataxic hemiparesis - location: Posterior limb of internal capsule, basilar pons, corona radiata, red nucleus, lentiform nucleus, superior cerebellar artery or anterior cerebral artery infarcts - presentation???

Answer 27

Combination of ipsilateral cerebellar and motor symptoms (weakness, clumsiness): • Affects legs more than arms • Onset over hours or days

Question 28

[lacunar stroke] Dysarthria/ clumsy hand - location: Basilar pons, anterior limb of internal capsule, corona radiata, basal ganglia, thalamus, cerebral peduncles - presentation???

Answer 28

Dysarthria and clumsiness of the hand (most prominent when writing)

Question 29

[lacunar stroke] Pure sensory storke - location: Contralateral thalamus, internal capsule, corona radiata, midbrain - presentation???

Answer 29

Numbness on one side of body (may develop tingling, pain, burning etc.)

Question 30

[lacunar stroke] mixed sensorimotor stroke - location: Thalamus and adjacent posterior internal capsule, lateral pons - presentation???

Answer 30

Ipsilateral hemiparesis/hemiplegia with sensory impairment

Question 31

Extradural (epidural haemorrhage) Often due to trauma → rapid onset of symptoms (medical emergency → refer to neurosurgeon for craniotomy): • Between the _____________ (due to arterial bleed from _____________) • Strips the dura away from the skull and builds pressure in the cranial cavity (may cause herniation around the tentorial notch resulting in death)

Answer 31

skull and dura mater; middle meningeal artery

Question 32

Subdural haemorrhage Often due to trauma → delayed onset of symptoms (retain patient overnight for observation): • Between the _______________ (due to venous bleed from _________)

Answer 32

dura mater and arachnoid mater; bridging veins

Question 33

Subarachanoid haemorrhage Often due to ruptured aneurysms (congenital weakness in vessel walls): • Between the arachnoid mater and pia mater (involving vessels at the _______________

Answer 33

base of the brain (Circle of Willis)

Question 34

Intracerebral haemorrhage: ________________ occurring beneath the pia mater

Answer 34

Spontaneous hypertensive event