Neuro - 20. Blood Supply PDF

BLOOD SUPPLY TO THE NERVOUS SYSTEM  20% of cardiac output & lung oxygen is for the brain Intricately controlled delivery – Monitoring of pressure changes in internal carotids – Monitoring respiratory gas levels 1min - loose consciousness 5 min - irreparable b...

BLOOD SUPPLY TO THE NERVOUS SYSTEM  20% of cardiac output & lung oxygen is for the brain Intricately controlled delivery – Monitoring of pressure changes in internal carotids – Monitoring respiratory gas levels 1min - loose consciousness 5 min - irreparable brain damage Blood   Internal carotids – anterior circulation  Vertebral arteries – posterior circulation  Linked by Circle of Willis – collateral supply  Posterior (vertebral) circulation is vital for life – supply brainstem and cerebellum  Vertebral arteries are at risk in the neck Anterior and posterior circulations Circle of Willis Circle of Willis  Vertebral arteries Basilar artery Anterior spinal artery Vertebro-basilar insufficiency (VBI) ‘Beauty parlour syndrome’ Circle of Willis  Give rise to: ◦ Ant. Spinal artery (most is via radicular ateries) ◦ Posterior inferior cerebellar (PICA) –lateral medullary infarct syndrome ( +posterior spinal artery) ◦ Ant inferior & superior cerebellar –ataxia/incoordination ◦ Pontine branches – paralysis/ V, VI, VII ◦ Post. Cerebral- supplies occipital lobe –cortical blindness Posterior circulation - Vertebral & basilar Posterior circulation – pons & cerebellum  Anterior cerebral – Contralateral spastic paralysis of leg. Expressive (Broca’s) aphasia if on left. Anterior circulation  Middle cerebral – contralateral spastic paralysis (leg spared), R = neglect of L side; L = expressive/receptive aphasia. Anterior circulation  No valves Veins drain into sinuses (dural walls) Sinuses drain into internal jugular vein Emissary veins link scalp & skull veins with dural sinuses –infection/thrombosis Some face /base of skull veins can drain into the cavernous sinus Veins  Spinal circulation – Posterior spinal artery – from PICA, forms plexus, supplies post 1/3 (dorsal column), rich collateral supply – Anterior spinal artery – from vertebral artery, supplies ant 2/3 – Radicular arteries – branch off aorta, most supply root only, 12 unpaired feed post spinal artery, 7-10 supply ant spinal artery spinal cord supply  Sudden onset (unless aortic atheroma) Radicular pain Para/quadriplegia Spinal shock flaccidity/arreflexia spasticity/hyperreflexia within days Pain/temp loss below (dorsal columns unaffected) Urinary retention Anterior spinal artery syndrome  T8 level – anterior spinal artery narrowest damage during hypertension Sacral arteries – sacral cord & cauda equina Posterior spinal artery syndrome rare – Loss of tendon reflexes/weakness, dorsal column loss Venous infarction rapid ‘total’ cord syndrome Spinal artery syndromes cont.  Syncope: Usually blood pressure regulation problem e.g ‘vasovagal’ Vasospasm: Migraine; Transient Ischaemic Attacks (resolve in 24 hours) Infarction (70% of strokes): atherosclerosis/ clots/ fat Haemorrhage (30% of strokes) Cerebrovascular disorders  ‘worst ever’, ‘like a hammer’, ‘new’ Stiff neck, SLR positive BP up, eyes red/bulging Decreased/loss of consciousness Papilloedema, fixed pupils, visual probs. Hx: head injury; PMHx/ Sx: risk factors There are more. Safe bet: REFER! Headaches & blood  Subarachnoid: Burst aneurysyms or congenital malformations that bleed Subdural: Torn, bleeding veins e.g. shaken baby syndrome Epidural: Usually bleeding middle meningeal artery e.g blow to side of head Pain, nausea, drowsiness etc etc. This can last for days & patients may visit a chiropractor! Heamorrhages   Hypertension  Diabetes melitus  Over 65 Check their BP  Heart disease  Get a decent  Oral contraceptives history  Cigarette smoking  TIAs  Symptoms – HA, neck pain, neuro signs(brain & cord), syncope Stroke risk factors