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Scenario aims

  • Describe the structure and function of cells of the central nervous system (CNS)
  • Describe the blood supply to the brain and explain the effects of occlusion of each of the major arteries
  • Explain the causes, consequences and likely outcomes of cerebrovascular diseases
  • Describe the functions of individual cranial nerves and explain the consequences of cranial nerve dysfunction
  • Evaluate scientific and ethical issues surrounding brain death and withdrawal of life support


Cerebrovascular Disease – “Stroke”

  • Definition:
    • An abnormality of the brain of acute onset caused by a pathological process affecting blood vessels
  • Causes:
    • Cerebral infarction resulting from impairment of blood supply and oxygenation of the CNS – 85%
    • Haemorrhage resulting from rupture of CNS vessels – 15%

Ischaemia and the CNS

  • Cerebral neurons rely on aerobic metabolism
  • Normal blood flow to CNS: 50 mL/100 g/min (i.e. 15% of cardiac output)
  • Auto regulation by cerebral vessels maintains blood flow across a wide range of blood pressure (so that with MAP = 60mmHg, you can still perfuse CNS)
  • Cerebral infarction is likely if:
    • blood flow falls to zero for 4‐10 minutes
    • blood flow falls below 16 mL/ 100 g/min for > 1 hour

Stroke - epidemiology

  • 7 % of all deaths in Australia (3rd ranked)
  • Incidence: approx. 100 per 100,000 population per year
  • Mortality: 20% in 1st 28 days; 37% in 1st yr
  • Morbidity: By the end of the first year, the majority of stroke survivors remain disabled
  • Recurrence: 17% in the first 5 years

Stroke ‐ Costs

  • Approx. 2% of total cost of disease in Australia (~$2 billion/yr)
  • Average cost of care (lifetime) per stroke survivor: $54,000‐$64,0001
    • Includes:
      • direct service use
      • care‐giver time
      • out‐of‐pocket payments
      • production losses
  • Total cost: approx. $555 million in the first year ($1.3 billion lifetime)
    • Includes:
      • acute hospital care ($154 million / yr)
      • rehabilitation ($156 million / yr)
      • nursing home care ($63 million / yr)

Cerebral infarction - risk factors

  • Atherosclerosis
    • Age, Hypertension, Tobacco smoking, Diabetes mellitus, Hypercholesterolaemia
    • Previous transient ischaemic attack or stroke (TIA is a warning sign that they're at very high risk of a stroke)
    • Narrowing of the carotid arteries (carotid stenosis; listen for turbulent flow over carotid arteries - angiography or ultrasound can confirm this)
  • Heart disease (increases risk of embolic stroke)
    • Atrial fibrillation (mural thrombus in LA)
    • Previous myocardial infarction (mural thrombus in LV)
    • Valvular disease (vegetations)

Cerebral Arterial Supply

  • Note anterior and posterior divisions of the blood supply
  • Circle of Willis - important in providing collateral flow if there is occlusion proximal to the circle of Willis

Stroke – Common Neurological Deficits

  • Hemiparesis: weakness in an arm and leg on one side of the body (contralateral to lesion)
  • Aphasia: difficulty in comprehending and/or formulating speech
  • Hemianopia: loss of the visual field on one side (contralateral to lesion)
  • Hemianaesthesia: loss of sensation on one side of the body (contralateral to lesion)
  • Sensory neglect: inattention to one side of the body (contralateral to lesion) - difficult for rehab
  • Carotid stenosis – narrowing of the internal carotid artery due to athero
  • Haematoma – accumulation of blood outsides the blood vessel (in tissue)
  • Haemorrhage – bleeding
  • Haemorrhagic transformation – reperfusion following an embolic cerebral infarction causing secondary haemorrhage in the infracted area
  • Hemiplegia – paralysis of muscles on one side of the body
  • Hydronephrosis – dilation of the renal pelvis and calyces caused by urine flow obstruction
  • Ischaemic stroke (cerebral) – necrosis of brain tissue due to inadequate blood supply caused typically by thrombotic or embolic arterial blockage
  • PEG tube – percutaneous endoscopic gastrostomy tube that is inserted into the stomach through the abdominal wall to enable direct feeding
  • Diplopia - double vision

Investigation

Non contrast CT brain

  • Woman had all of the above signs
  • Cerebral CT allows us to distinguish a hemorrhage. This person had a clot in the middle cerebral artery (secondary to atrial fibrillation)
  • CT angiogram shows the loss of perfusion of distal middle cerebral artery
  • Red area shows the part of the brain that is most at risk
  • Give the patient a clotbuster (thrombolysis) drug
    • Carries a great risk in that you can cause haemorrhage somewhere else
  • Mechanical embolectomy - using catheter, you remove the clot
  • Diffusion MRI of brain shows the parts of the brain that are ischaemic/necrotic - she has long term speech disturbance.
  • There was a lot more of the brain at risk, but thankfully it wasn't as bad as that. Deficit results
    • Embolectomy has less risk than thrombolysis
  • Reperfusion injury most common with coronary artery stenosis that is opened up (chronic low flow followed by opening), not as common with thrombectomy in stroke

Stroke unit meeting

Case 1

  • 80 years old, left sided ischaemic stroke
    • Atrial fibrillation - major risk factor for embolic stroke
    • HF, ischaemic cardiomyopathy
    • Implanted cardiac defibrillator, AF
    • Conscious, poorly responsive/drowsy
    • CT showed recent infarct, likely embolic from heart
    • Not on anticoagulation (Warfarin), if haemorrhagic anticoagulation could make it worse
      • Warfarin significantly decreases risk of coagulation in AF
  • Complications
    • Pneumonia
    • RHS hemiparesis and aphasia
    • Function previously was reasonable, future is unclear
    • Cannot swallow safely – fed by nasogastric tube to prevent aspiration --> poor prognosis
    • No improvement
  • Family aware that he is unwell and may not survive
    • Agree to conservative management (NFR: not for resuscitation); family conference to decide what you think that patient wants and what the patient wants
  • Many end of life/palliative care issues

Assist swallowing screening tool

  • Dysphagia = problem swallowing (different to dysphasia)
  • Swallow Screening reduces risk of Aspiration Pneumonia - big deal

Case 2

  • 73 woman, fractured neck of femur, surgery
    • post-operative, RHS weakness from left cerebral haemorrhagic stroke
    • planning for PEG tube since her current oral intake is not enough to sustain her
      • nasogastric tube is unpleasant
    • Speech pathologist raised quality of life issues with a PEG tissue
      • never swallow again, never taste again

Case 3

  • 95 man, LHS hemiparesis, alert and responsive
    • no cerebral changes, echocardiogram normal
    • carotids, 15% left stenosis, 15-49% on the right sinus rhythm
    • accepted for rehabilitation



Case 4

  • 78 male, aphasia and confusion, with no weakness
    • unable to describe as confused since difficulty speaking (remember this - the difference is important)
  • Prosthetic metal aortic valve + warfarin
    • coagulation test was low - showed potential for clots on the valve
      • probably not taking Warfarin reliably
  • Treatment
    • Warfarin restarted
  • INR became too high and abdominal pain developed
    • Anaemia (low haemoglobin)
    • Left sided psoas haematoma with kidney obstruction and hydronephrosis
    • Reversal of anticoagulation causes risk of clots, inadequate reversal means continued haemorrhage into abdomen (competing needs: haemorrhage and stroke)
  • Expressive dysphasia, repetitive speech, other issues, however

Case 5

Females have increased risk of stroke postpartum

  • 30, 2 weeks post-partum right hemiparesis and dysphasia
    • right hemianopia
    • can understand
    • ischaemic stroke, haemorrhagic transformation
  • surgery
    • insertion of a ventricular drain – subarachnoid haemorrhage (stroke of the young)
    • currently septic, infection complications
    • prognosis not so good

NB: stroke death rate is 20% normally, or 30% with AF.

Other terms

  • Quadrantanopia means a loss of a quadrant of vision
  • Ischaemia may become a haemorrhagic stroke due to vessel wall weakening
  • Dysphasia – language disorder, not as severe as aphasia
  • Dysarthria (speech articulation problems) and difficulty swallowing are mechanical problems to do with the facial muscles

Stroke and function

  • Motor function affected
  • Sensory and coordination may affect gait and function
  • Speech
    • Language problems – comprehension (receptive dysphasia), word output (expressive dys/aphasia)
    • Mechanical – slurred speech (dysarthria), swallowing impairment
  • Visual changes – hemianopia, diplopia
  • Cognitive disturbance – confusion, delirium

Immobility complications

  • Bed/chair bound, reduced mobility
    • Contractures (muscle tightening)/muscle wasting
    • Skin breakdown and pressure wounds
    • Thromboembolic disease (DVT, pulmonary embolism)
    • Aspiration pneumonia
    • Malnutrition
    • Depression, grief, pain



Psychosocial

  • Terrified of impairment (anatomical/physiological)
    • Impact is mostly due to disability (clinical)
  • Social isolation with reduced participation in social/family networks
  • Often can require long-term care

Rehabilitation

  • Definition: the process of recovering function through multidisciplinary therapy programmes
    • Adaptation to loss of function not recovered
  • Aims to improve residual ability and adaptations to function more independently in spite of disability
    • Helps prevent complications
  • A functional review should be conducted of daily activities: shower, dressing, toilet, food, shop, clean, medications, bills

Prevention

  • Prevent stroke from AF and prosthetic metallic valves with warfarin
    • Warfarin has risks with the elderly, however, causing more falls/bleeding
  • Secondary prevention of ischaemic stroke with Aspirin or Clopidogrel (platelet inhibitors)
  • Stroke reduction with carotid surgery for severe carotid stenosis
  • Hypertension/diabetes, cigarettes control [risk factors]
  • Cardioembolic stroke: from atrial fibrillation/ prosthetic metallic valve – very significant stroke risk, reduced with Warfarin.
  • Risks of Warfarin in frail elderly (falls)
  • Ischaemic stroke secondary prevention with Aspirin or Clopidogrel (platelet inhibitors)
  • Stroke reduction with carotid surgery (0.1% surgical risk vs 10% stroke risk per annum) for 90% carotid stenosis
    • Carotid stenting
  • Hypertension, Diabetes, cigarettes control