blood supply to the brain and spinal cord and vascular lesions

blood supply to the brain

arises from the Aortic notch, divides into common Cortaid arteries and subclavian arteries

common carotid arteries bifurcate into

internal and external carotid arteries

internal carotid arteries

supplies most of the telencephalon and much of the dicencephalon

the vertebral arteries

supplies the brainstem and cerebellum

parts of the diencephalon, spinal cord and occipital and temporal lobes

branches of the internal carotids

enter the brain through the petrous portion of the temporal brain

• enter subarachnoid space

further divides into the: anterior cerebral arteries and the middle cerebral arteries

supply most of the cerebrum

vertebral basilar system

arise from the subclavian arteries

at the junction between medulla and pons, fuse and from the basilar arteries

bifurcates into two posterior cerebral arteries (PCA)

Branches of the vertebral arteries

posterior inferior cerebellar arteries (PICA)

anterior inferior cerebellar arteries (AICA)

sup cerebellar arteries

pontine arteries

internal auditory arteries

PICA

arises from: vertebral artery

supplies inf surface of cerebellum

also supply lateral medulla

AICA

arise from basilar artery just rostral to the origin

supplies ant portions of the inf surface of cerebellum and caudal pons

sup cerebellar arteries

arises from basilar artery

supplies sup surface of the cerebellum, caudal midbrain and rostral pons

pontine arteries

supplies pons

internal auditory arteries

supplies inner ear

occlusion can lead to vertigo and ipsilateral HL

Circle of Willis

mechanism that joins the subclavian artery system with the carotid artery system

at base of the brain, surrounding the optic chiasm

connects the: ant cerebral, internal carotid, post arteries of both sides

connected by 1 ant communicating artery: Right and left ACAs

paired post communicating arteries: internal carotids and PCAs

Hemispheric blood supply: ACA

ant cerebral artery (ACA)

runs medially, supplies the medial aspect of the frontal and parietal lobes

some extend onto the dorsolateral surface of the hemisphere

occlusion impacts portions of the precentral and post central gyri

causes restricted and contralateral motor esp lower extremities and somatosensory deficits

Hemispheric blood supply: MCA

emerges from the lateral sulcus

supplies most of the lateral surface of the cerebral hemisphere

supplies most of the precentral and postcentral gyri

causes major motor and somatosensory deficits

left mca lesion most likely results in aphasia

important branches of mca

lenticulostriate arteries:

supply deep structures of the diencephalon and telencephalon

• basal ganglia, internal capsule and insula

Strokes

lesion results in devastation in the internal capsule

hemispheric blood supply: PCA

supplies the medial and inf surfaces of the occipital and temporal lobes

rostral midbrain

post parts of the diencephalon

splenium of corpus callosum

occlusion can result in visual field losses

lesion involding pica or aica

ataxia

lesion involcving pca

hemianopsia

alexia without agraphia

amnesia

lesion involving mca

aphasia

heminplegia, hemiparesis, hemianaesthesia

lesion involving aca

hemiplegia and hemianaesthesia

venous system

cerebral veins are divided into: superficial veins

drain the blood from the skin

empties into the sup sagittal sinus

deep veins:

drains internal structures

empty into the straight sinus

blood flow control to the cns

autoregulation: Allows blood vessels to constrict in response to
increased blood pressure & relax in response to
decreased pressure

metabolic mechanism: vessels dilate with increased co2 levels and constrict with decreased co2 lvls

neural control is minor importance

perfusion pressure

normal blood pressure in brain

difference bt the arterial, intracranial, venous pressure allows blood to circulate

hypoperfusion pressure

no pressure between the 3 systems

causes decrease in the circulation of blood

distal branches of the cerebral arteries are affected

water shed lesions occur

causes diffuse sign behaviorally

cerebrovascular accidents cva

ischemic strokes caused by sudden vascular insuffiency

thrombosis: gen caused by occlusion of blood vessels at the site

typically caused by atherosclerosis

embolism: caused by heart disease

embolus is moved to the distant part of the body and gets lodged

behavioral signs are similar to the thrombosis

cerebrovascular accidents

transient ischemic attacks TIA: temp occlusion of blood vessels

deficits persist for mins to hours

followed by complete recovery

caused by minute emboli which become broken down

intracerebral hemorrhage:

bleeding in brain

commonly result from the rupture of small perforating arteries bc of hypertension

aneurysm

balloon like swelling of arterial walls

occur most at or near the bifurcation of arteries

cause neuro deficits by compressing brain structures and rupturing and causing subarachnoid hemorrhage

arterial venous malformation avm

abnormal coupling of the arterial and venous systems - congenital malformation

hemorrhage my occur