Vasculature To The Brain And SC Flashcards
What is the primary blood supply to the brain?
ICA’s (80%) and vertebral arteries (20%)
What is the course of the ICA and vertebral arteries?
Pierce dura mater -> run in subarachnoid space and their branches penetrate into the brain parenchyma
Surrounded by perivascular (Virchow-Robin) space
What are the components of the BBB?
Endothelial cell layer, basement membrane, pericyte, perivascular processes of astrocytes and oligodendrocytes
Which arteries form the circle of Willis?
Anterior communicating, posterior communicating, anterior cerebral, posterior cerebral and ICA
What is the clinical significance of the variation seen in the circle of Willis?
The ability of the unaffected portion of the circulation to hyper-perfuse the affected circulation is problematic -> may result in hypo-perfusion with associated ischemia or cerebral edema -> serious manifestations of diminished cerebral blood flow and may result in ischemic stroke or death
Describe regional or focal ischemia
Seen in strokes where there is occlusion of a large nutrient artery
Results in ischemic penumbra (the tissue surrounded the ischemic territory which is too ischemic to function but critically viable)
Describe treatments for regional/focal ischemia and the ischemic penumbra that results
Stroke therapy is directed at rescuing the penumbra by improving tissue acidosis and O2 delivery
Ca channel and NMDA receptor blocking drugs may prevent further neuronal damage
Autoregulation dysfunction and edema due to ischemic tissue acidosis and resultant luxury perfusion or adjacent normal tissue
What occurs in global ischemia?
Distal areas of cerebral arterial circulation are hypoperfused and vulnerable to watershed infarction
Which areas of the brain are consistently damaged in severe ischemic injury?
Certain areas of the brain (distal branches of the cerebral arteries) and particular neuronal populations (pyramidal cells of the hippocampus especially the CA1 or Sommer’s sector)
Ischemia of the arterial supply of the SC most commonly occurs adjacent to what?
The enlargements at C2-3, T1-4 and L1
What are watershed regions in the cerebrum?
Border zone regions supplied by major cerebral arteries where blood supply is decreased (due to infarctions)
The farthest regions supplied by arterial blood supply
Ligation of which artery is being used for treatment of Parkinson’s?
AChA
Infarction of the AChA is characterized by what?
Triad of hemiplegia, hemianesthesia and contralateral hemianopia
May also be associated with left neglect syndrome (right sided lesions) and speech disorders
What does the PCoA supply?
Internal capsule and basal ganglia
Which CNs is the ACA located near and what does it supply?
Located next to olfactory and optic nerves
Supplies anteromedial frontal cortex, anterior cingulate gyrus and paracentral lobe
What is the clinical significance of the anterior cerebral A?
Occlusion of the ACA or superior sagittal sinus may result in sensory and/or motor deficits in the contralateral leg and foot
Highest incidence of cerebal aneurysm (35%)
What does the middle cerebral A supply?
Internal capsule, corpus striatum, thalamus, primary auditory cortex, association cortex primary motor and primary somesthetic cortices, premotor and prefrontal cortices, Broca’s area, supramarginal and angular regions, Wernicke’s region
What does a thrombosis in the central artery (of the MCA) cause?
Contralateral spastic paralysis and/or paresthesia of the face and upper 1/2 of body
What causes Wernicke’s aphasia?
Caused by damage to the angular A (of the MCA)/obstruction of the MCA in the dominant hemisphere
What is Wernicke’s aphasia?
A receptive language disorder in which pts are talkative/fluent but lack content or meaning in spoken and written language
Language pattern tends to have numerous inappropriate word choices and neologisms (new word creations)
Occlusions in the MCA may result in what?
Sensory and/or motor deficits in the contralateral upper limb and head
A thrombosis in the MCA results in what?
Expressive or Broca’s aphasia
A motor language disorder in which pts have a frustrating problem in initiating speech motor patterns
Certain automatic sometimes profane speech patterns may persist
Which arteries are of the anterior circulation?
Branches of the ICA including AChA, PCoA, ACA and MCA
Which arteries are of the posterior circulation?
Vertebral A, PICA and basilar A
What does the anterior spinal A supply?
Central gray matter and anteromedial portion of white matter of the SC
Which artery can be compromised during AAA repair or secondary to thoracolumbar fracture?
Greater anterior A of Adamkiewicz
What does the posterior spinal A supply?
Dorsal roots, posterior 1/3 of spinal cord (most of the posterior column)
An angiogram showing PICA displacement may indicate what?
A tumor
What does the posterior inferior cerebellar A supply?
Posteroinferior portion of cerebellum, some medulla, choroid plexus of 4th ventricle
Thrombosis of the posterior inferior cerebellar A may result in what?
Lateral medullary (Wallenberg) syndrome
What does the posterior cerebral A supply?
Internal capsule, thalamus, choroid plexus of lateral ventricle and upper midbrain
Also supplies the inferior temporal cortex, visual association cortex and primary visual cortex
All veins of the SC drain into what?
The internal venous plexus of Bateson (located in the epidural surface)
Describe the superficial venous drainage of cerebral hemispheres
Drains most of the cortex of the lateral cerebral hemispheres
Empties into the cavernous sinus, superior sagittal sinus, transverse sinus via the superior and inferior anastomotic veins
Thrombosis of the superior sagittal or right transverse sinus results in what?
Cortical ischemia and/or necrosis
Thrombosis of the straight sinus or left transverse sinus results in what?
Ischemia/necrosis of deep cerebrum
Usually fatal
