5. 2 Anatomy of Cerebral Blood Flow Flashcards
What is the course of the internal carotid arteries?
Bifurcation of common carotid arteries (C4) –> Within carotid sheath –> carotid canal –> pass anteriorly in the cavernous sinus
What are the branches of the ICA
- 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)
What is the course of the vertebral arteries?
1st part of subclavian artery –> transverse foramen (C1-C6) –> foramen magnum
What are the branches of the vertebral arteries?
- 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
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)
pituitary gland
What are the components of the circle of willis?
- Anterior cerebral arteries
- Internal carotid arteries
- Posterior cerebral arteries
- Anterior communicating
- Posterior communicating
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)
Sphenoidal air sinus and the sella turcica (pituitary fossa);
ICA, CN III, IV, VI
Where does the venous drainage of the brain occur?
cerebral veins, which empty into the dural venous sinuses (within the dura mater) then the IJV
where does the superior cerebral veins drain to?
Superior surface to superior sagittal sinus
where does the superficial middle cerebral vein drain to?
Lateral surface to cavernous or sphenopalatine sinuses
Where does the inferior cerebral veins drain to?
Inferior surface to cavernous or transverse sinuses
Where does the Superior anastomotic vein (of Trolard) drain to?
Superficial middle cerebral vein to superior sagittal sinus
Where does the Inferior anastomotic vein (of Labbé) drain to?
Superficial middle cerebral vein to transverse sinus
Where does the subependymal veins drain to?
Receive blood from medullary veins and carry it to the dural venous sinuses:
• Great cerebral vein (of Galen): to straight sinus
Where does the Medullary veins drain?
Deep areas of brain to subependymal veins
Where does superior sagittal sinus drain?
Runs towards back of head → confluence of sinuses (opening within the dura mater)
Where does inferior sagittal sinus drain?
Runs towards back of head → straight sinus → confluence of sinuses (opening within the dura mater)
Where does confluence sinuses drain?
Drains laterally via transverse sinus → sigmoid sinus → jugular foramen → IJV
which part of the brain does the anterior cerebral artery supply?
thin 1cm outer lateral aspect of the lateral brain, wide circulation medially and a large part of the anterior cerebral cortex
which part of the brain does the middle cerebral artery supply?
large part of lateral brain, small component of midline brain
which part of the brain does the posterior cerebral artery supply?
posterior brain (occipital lobes and inferior temporal lobes)
what is the clinical presentation of the anterior infarct of the brain?
- 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)
what is the clinical presentation of the middle (classic) infarct of the brain?
• 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
what is the clinical presentation of the posterior infarct of the brain?
• 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)
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)
chronic hypertension;
Treatment: tissue plasminogen activator (alteplase, streptokinase);
[lacunar strokes]
Pure motor stroke/ hemiparesis
- location: Posterior limb of internal capsule, basilar pons, corona radiata
- presentation: ???
Contralateral hemiplegia or hemiparesis (face, arm, leg):
• Dysarthria, dysphagia, transient sensory symptoms
[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???
Combination of ipsilateral cerebellar and motor symptoms (weakness, clumsiness):
• Affects legs more than arms
• Onset over hours or days
[lacunar stroke]
Dysarthria/ clumsy hand
- location: Basilar pons, anterior limb of internal capsule, corona radiata, basal ganglia, thalamus, cerebral peduncles
- presentation???
Dysarthria and clumsiness of the hand (most prominent when writing)
[lacunar stroke]
Pure sensory storke
- location: Contralateral thalamus, internal capsule, corona radiata, midbrain
- presentation???
Numbness on one side of body (may develop tingling, pain, burning etc.)
[lacunar stroke]
mixed sensorimotor stroke
- location: Thalamus and adjacent posterior internal capsule, lateral pons
- presentation???
Ipsilateral hemiparesis/hemiplegia with sensory impairment
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)
skull and dura mater;
middle meningeal artery
Subdural haemorrhage
Often due to trauma → delayed onset of symptoms (retain patient overnight for observation):
• Between the _______________ (due to venous bleed from _________)
dura mater and arachnoid mater;
bridging veins
Subarachanoid haemorrhage
Often due to ruptured aneurysms (congenital weakness in vessel walls):
• Between the arachnoid mater and pia mater (involving vessels at the _______________
base of the brain (Circle of Willis)
Intracerebral haemorrhage: ________________ occurring beneath the pia mater
Spontaneous hypertensive event
