1. CEREBRAL CIRCULATION

2. FACTS ABOUT BLOOD SUPPLY
OF BRAIN
 Brain – 2% of body weight
 Receives 17% of cardiac output
 Consumes 20% of entire Oxygen used by the body
 10 seconds of interruption in blood flow leads to
unconsciousness
 Most neurologic disorders are due to vascular
lesions

3. ANTERIOR AND POSTERIOR
CIRCULATIONS
Anterior – Internal carotid arteries
Posterior – Vertebral arteries

5. INTERNAL CAROTID ARTERY
Course
 Entry – carotid canal
 Middle cranial fossa- beside dorsum sellae
 Enters cavernous sinus
 Approaches medial side of anterior clinoid
process

6.  Pierces dura and arachnoid maters
 Moves lateral to optic chiasma
 Divides into Anterior and Middle cerebral
arteries

8. BRANCHES OF INTERNAL CAROTID
ARTERY[PRIOR TO BIFURCATION]

9.  Occasionally, Anterior choroidal artery supplies
2. Rostral midbrain
3. Ventral thalamus
4. Subthalamus

10. ARTERIAL
‘CIRCLE’/’CIRCLE’ OF
WILLIS

11. “CIRCLE” OF WILLIS
 Looks more like a polygon
 Connects anterior and posterior circulations

12. COMPONENTS
 From anterior
2. Anterior communicating artery
3. Anterior cerebral artery
4. Posterior communicating artery
5. Posterior cerebral artery

13.  Alternate route – inadequate, especially in the
elderly [atherosclerosis]
 Variations
3. In approximately 33% persons Posterior cerebral
artery arises from Internal carotid artery
4. One Anterior cerebral artery may be small-
anterior communicating artery is wider

15. TERRITORIES OF
CEREBRAL ARTERIES

18. ANTERIOR CEREBRAL ARTERY
 Midline proximity [longitudinal horizontal
fissure]
 Joined together by anterior communicating
artery
Branches
4. Medial striate/recurrent artery of
Heubner→ventral part of head of caudate
nucleus, putamen, anterior limb and genu of
internal capsule

20. AREA SUPPLIED
 Medial part of orbital surface of frontal lobe
[includes olfactory bulb and tract]
 Medial surfaces of frontal and parietal lobes
 Corpus callosum
 A strip on lateral surface

21. FUNCTIONAL AREAS SUPPLIED
 Supplementary and cingulate motor areas
 Dorsal parts of primary motor and sensorimotor
areas

22. OTHER ASSOCIATED DEFICITS IN
ACA BLOCK
 Mental confusion and dysphasia[functional loss
in prefrontal cortex, cingulate gyrus,
supplementary motor area]

23. EFFECTS OF OCCLUSION
 Paralysis and sensory deficits in contralateral
leg, perineum
 Urinary incontinence [inadequate perineal
sensation, defective cortical control of pelvic floor
muscles]
If obstruction is proximal to anterior
communicating artery [blocked medial striate
artery]
 UMN weakness of face, tongue and upper limb
[lesion in or near genu]
 Ipsilateral anosmia [maybe]

24. POSTERIOR CEREBRAL
ARTERY

26. BRANCHES
 Central branches supply
2. Midbrain
3. Pineal gland
4. Lateral geniculate body
5. Lentiform nucleus [partly]
6. Thalamus [partly]

27.  Temporal branches→ inferolateral and medial
surfaces of temporal lobe, much of
parahippocampal gyrus
 Calcarine and parieto-occipital branches→
peripheral strip on lateral surface
 Calcarine branch supplies all of primary
visual cortex and some of Visual association
cortex

28.  Posterior choroidal artery supplies
d Choroid plexus of inferior horn of lateral
ventricle
f Choroid plexus of 3rd ventricle
f Thalamus
f Fornix
f Tectum of midbrain
anastomoses with Anterior choroidal artery

29. EFFECTS OF OCCLUSION
 Blindness in contralateral visual fields of both
eyes – homonymous hemianopia
 Disturbance of memory – transient
 In case of dominant hemisphere being affected,
the infarct extends into corpus callosum→
disconnection of contralateral visual area from
language area of dominant hemisphere→ alexia
in addition to homonymous hemianopia

30. SPECIAL CIRCUMSTANCES
 Expanding space-occupying lesion in
supratentorial compartment→ herniation of
uncus and midbrain→ compression of one or both
PCA→ necrosis of areas supplied [even after
surgical correction of cause]→ cortical
blindness+inability to form new memories
 Traumatic Intracranial hemorrhage can lead to
the same consequences

31. MIDDLE CEREBRAL
ARTERY

32.  Larger, more direct continuation of ICA
 Occupies lateral sulcus
 Central branches →Head of caudate
nucleus,Putamen, Lateral pallidum, Internal
capsule [anterior limb, genu, posterior limb],
External capsule, Claustrum, Lateral
hypothalamus

33. FUNCTIONAL AREAS SUPPLIED
 Most of primary motor and premotor areas
 Frontal eye field
 Primary somatosensory area
 Geniculocalcarine tract
EXCEPT motor and sensory cortex for
lower limb and perineum
In most persons, left MCA supplies all
cortical areas concerned with language
[Wernicke’s,Broca’s]

34. EFFECTS OF OCCLUSION
 Contralateral paralysis of lower face, upper limb
 General somatosensory deficits in the same areas
 Astereognosis
 Hemianopia in contralateral visual fields of both
eyes
 Global aphasia if dominant hemisphere involved
 Aprosodia if non-dominant hemisphere involved

35.  Cortical neglect, if right hemisphere involved
 Conjugate eye movements affected[ at rest, eyes
turn towards the side of lesion]
 Hearing unaffected [bilateral representation]
 Obstruction to central branches- contralateral
hemiplegia without aphasia