deck_3166997 Flashcards
What are the main blood vessels that supply the brain?
Internal carotidsVertebral arteries
Give the branches of the internal carotid arteries
Anterior cerebralMiddle cerebral (continuation)OpthalmicPosterior communicating
What does the anterior cerebral artery supply?
Medial surfaces of frontal and parietal lobes
What does the middle cerebral artery supply?
Lateral surfaces of the cerebral cortex
Give the branches of the vertebral arteries
Join to form the basilar arteryPosterior cerebral arteries
What does the basilar artery supply?
Medulla Brainstem
What does the posterior cerebral artery supply?
Inferior surface of brainOccipital lobe
Where do the internal carotid arteries enter the skull?
Carotid canal
Where do the vertebral arteries enter the skull?
Foramen magnum
Why is the circle of willis important?
Provides collateral circulation if there is a blockage to one part of a blood vessel- usually inadequate after a sudden occlusion
Describe autoregulation
Cerebral blood vessels will constrict and dilate in response to changes in cerebral perfusion pressure so that it can maintain a sufficient perfusion.
Decreased CPP?
Vasodilation
Increased CPP?
Vasoconstriction
Define cerebral perfusion pressure
The net pressure gradient causing cerebral blood flow to the brainMean arterial pressure minus intracranial pressure
Define stroke
A clinical syndrome of abrupt loss of focal brain function lasting over 24 hours or causing death
What causes a stroke?
- Spontaneous haemorrhage into brain tissue2. Inadequate blood supply
What are the different types of stroke?
IschaemicHaemorrhagic
Describe ischaemic stroke
80-85% of strokesDue to blockage of blood supply- large vessel atheroma or embolism80% = atheroma20% = AF
Describe haemorrhagic stroke
15% of strokesRupture of cerebral blood vessels Primary = no structural lesionSecondary - structural lesion is present
What are the main causes of haemorrhagic stroke?
Hypertensive causes (40%)- microaneurysmsLarge aneurysms (15%)Anticoagulant/thrombolytic causesDrugs e.g. cocaine, amphetaminesTumour
Define a TIA
Sudden onset focal disturbance of brain function which resolves completely within 24 hours Most within 20 mins to 2 hours
Give some symptoms that occur if the site of the stroke is in the frontal lobe
- Speech impairment- personality changes- Movement impairment (motor control area)
Give some symptoms that occur if the site of the stroke is in the Parietal lobe
Eye sight problems- superior optic radiation- inferior homonymous hemianopia
Give some symptoms that occur if the site of the stroke is in the occipital lobe
Homonymous hemianopia
Give some symptoms that occur if the site of the stroke is in the cerebellum
Cerebellum contains: cardiac and respiratory control centresMotor and sensory tractsCranial nerve nuclei- Can have damage associated with all of these
Give some symptoms that occur if the site of the stroke is in the temporal lobe
Taste and smell changesWernickes area Inferior optic radiation- superior homonymous hemianopia Auditory and vestibular function
What happens when you get damage to wernicke’s area?
Receptive aphasia- Pt is unable to understand language in the written or spoken form- Will be able to speak with normal syntax and intonation but the words will not make any sense
What are the different classifications of strokes?
Total anterior circulation strokePartial anterior circulation strokeLacunar strokePosterior circulation stroke
Give the cause and presentation of a total anterior circulation stroke
Proximal occlusion of internal carotid or prox middle cerebral artery. Causes: contralateral hemiparesiscontralateral hemianopiahigher cerebral dysfunction e.g. dysphasia and dyspraxia
Give the cause and presentation of a partial anterior circulation stroke
Occlusion of a branch of the MCSASymptoms - Two of:- contralateral hemiparesis- contralateral hemianopia- higher cerebral dysfunctionIn face of arm or leg only Or have isolated cortical signs
Give the cause and presentation of a lacunar stroke
Occlusion of a single perforating artery, affects deeps trcutires of the brain e.g, basal ganglia, pons, thalamusSymptoms:Pure motorPure sensorySensorimotorHemiparesis
Give the cause and presentation of a posterior circulation stroke
Occlusion of a vessel found in the posterior circulation of the brainSymptoms:Affects brainstem, cerebellum of occipital lobe
Give some risk factors for stroke
AgeGenderFamily historyPrevious stroke/TIASmokingSedentary lifestyleHeavy alcohol intakePoor dietHypertension HypercholesterolaemiaDiabetes mellitusArrhythmia - AF
What are some differentials for stroke?
Hypoglycaemia and metabolic disturbancesMigraine auraEpilepsySpace occupying lesionDemyelination - MS
What will a CT scan show in a stroke?
Will show haemorrhage instantlyCan visualise an infarct (rarer to see)
What will an MRI scan show?
Will be able to visualise an infarct
Why is raised ICP a problem?
Skull is a rigid structure with a fixed volumeVolume is determined by brain, CSF and bloodChange in vol of one must be accompanied by an equal an opposite change in the other two
What is normal ICP?
0-10mmHg
Where are the three main areas where compression and herniation can take place?
Cingulate gyrusUncusCerebellar tonsils
Describe a cingulate gyrus hermiation
Brain is pushed away from lesion and herniates under the falx cerebri to the opposite hemisphere. This is a subflacine herniation.
Describe a central herniation
Brain herniates down between the tentorium cerebelli
Describe an uncal herniation
Brain herniates around the tentorium cerebelli, from one side
Describe a tonsillar herniation
Brain is forced downwards and herniates through the cerebellar tonsils through the foramen magnum.
Give some clinical signs of ICP
Loss of function (motor and sensory)Change in behaviourDrop in level of consciousnessChange in pupil reactionChanges in BP, pulse and breathing
How does the brain get injured?
Direct injury due to the brain being shaken inside the skull Direct injury leads to oedema and haemorrhage due to rupture of arteries or veins. Extra or subdural haematoma, causing increase ICP
What are the arteries that supply the spinal cord?
Anterior spinal artery Two paired posterior spinal arteries Anterior and posterior medullary arteries
What areas do each of the spinal arteries supply?
Ant = anterior two thirdsPost = posterior third
What gives rise to the anterior spinal artery?
Union of branches of the vertebral arteries- runs in the anterior median fissue
What gives rise to the posterior spinal arteries?
Branch of:- vertebral artery- posteroinferior cerebellar artery
Describe the ant and post medullary arteries
Branch from the aorta- main circulation to the spinal cord
Describe the artery of adamkiewicz
Greater anterior segmental medullary artery- arises in lower thoracic or upper lumbar segment, usually on the left- reinforces circulation to the lower spinal cord - branches from the segemental spinal artery
Describe spinal artery sydrome
Occlusion of the anterior spinal artery. Causing ischaemia and infarction.
What symptoms arise as a result of anterior spinal artery syndrome?
Get spinal shock initially- flaccid weakness, areflexia and anaesthesia Followed by complete motor paralysis - corticospinal tractLoss of pain and temperature- ant and lat spinothalamic tractsGet UMN signs and muscle atrophy
Give some causes of anterior spinal artery symdrome
Diseases of the aorta- aneurysm, trauma, dissection, atherosclerosisAortic surgeryVasculitisSCDHypotensionCardiac emboliDisc herniation which compresses vessels
What are some signs that can be seen in brainstem infarctions?
Lateral medullary syndromeLocked-in syndrome
Describe lateral medullary syndrome
Due to occlusion of posterior inferior cerebellar artery. Causes acute vertigo as well as cerebellar signs.
Describe vascular dementia
Multiple large infarcts can lead to a generalised loss seen with advanced cerebrovascular disease. Each infarct causes a progression of the condition leading to dementia, pseudobulbar palsy and shuffling gait.
What causes intracerebral haemmorrhages?
Degeneration of small deep penetrating arteries leading to a massive bleed. Usually due to chronic hypertension and occur at certain sites (basal gangli, pons, cerebellum, subcortical white matter)
Describe a decorticate response
Severe head injury or after a large infarct- destroy connections between thalamus and cortex- isolates cortex from lower brain and spinal cord- arms are flexed, legs are extended - damage to corticospinal and rubrospinal tracts
Describe a decerebrate response
Damage to lower parts of brain or brainstem- complete loss of descending inhibition on descending motor tracts - complete extension of lower limbs, upper limbs and headBrainstem damage
What can be indicated by a progression from a decorticate to decerebrate response?
Indicates uncal or tonsillar brain herniation
