Cerebrovascular Event (Stroke)

Clinical syndrome caused by disruption of blood supply to the brain, characterised by rapidly developing signs of focal or global disturbance of cerebral functions, lasting for more than 24 hours or leading to death

Aetiology

  • 85% of strokes are ischaemic - occur when blood supply in a cerebral vascular territory is reduced secondary to stenosis or complete occlusion of a cerebral artery
    • 25% of ischaemic strokes are caused by intracranial small vessel atherosclerosis
    • 50% of ischaemic strokes are caused by large vessel atherosclerosis e.g. carotid artery stenosis
    • 20% of ischaemic strokes are cardio-embolic e.g. in atrial fibrillation there is stasis of blood flow in the left atrium, predisposing to thrombus formation in the left atrium, and subsequent embolisation to the brain
    • Rare causes of ischaemic stroke include primary vascular causes (such as vasculitis and arterial dissection) and haematological causes (prothrombotic states)
  • 15% of strokes are haemorrhagic - occur when there is rupture of a cerebrospinal artery
    • Primary haemorrhage accounts for about 10%
    • Subarachnoid haemorrhage accounts for approximately 5%
    • The remainder are of uncertain type

Risk factors

  • Strong risk factors for ischaemic stroke include: age, male sex, family history of ischaemic stroke, hypertension, smoking, diabetes mellitus, and atrial fibrillation
  • Weaker risk factors for ischaemic stroke include: hypercholesterolaemia, obesity, poor diet, oestrogen-containing therapy, and migraine

Pathophysiology

Laterality

  • Important in prognosis/management
  • Dominant hemisphere (left) cortical events often affect language - major implications for rehabilitation
  • Non-dominant hemisphere (right) cortical events affect spatial awareness

Symptoms depend on which brain region is affected

  • Anterior or middle cerebral artery stroke → numbness, sudden muscle weakness
  • Broca’s area (left frontal lobe) → slurred speech
  • Wenicke’s area (left temporal lobe) → difficulty understanding speech
  • Posterior cerebral artery stroke → affects vision

Clinical presentation

Stroke symptoms are typically asymmetrical:
  • Sudden weakness of limbs
  • Sudden facial weakness
  • Sudden onset dysphasia (speech disturbance)
  • Sudden onset visual or sensory loss

Total anterior circulation syndrome (TACS)

  • Involves the anterior AND middle cerebral arteries on the affected side
  • Defined by:
    • Contralateral hemiplegia or hemiparesis, AND
    • Contralateral homonymous hemianopia, AND
    • Higher cerebral dysfunction (e.g. aphasia, neglect)
  • Most severe type of stroke with only 5% of patients being alive and independent at 1 year

Partial anterior circulation syndome (PACS)

  • Involves the anterior OR middle cerebral artery on the affected side
  • Defined by:
    • 2 out of the 3 features present in a TACS OR
    • Higher cerebral dysfunction alone e.g. dysphagia

Posterior circulation syndrome (POCS)

  • Involves the vertebrobasilar arteries and associated branches (supplying the cerebellum, brainstem, and occipital lobe)
  • Defined by:
    • Cerebellar dysfunction, OR
    • Conjugate eye movement disorder, OR
    • Bilateral motor/sensory deficit, OR
    • Ipsilateral cranial nerve palsy with contralateral motor/sensory deficit, OR
    • Cortical blidness/isolated hemianopia

Lacunar infarcts (LACI)

  • Small infarcts around the deeper parts of the brain (basal ganglia, internal capsule, thalamus and pons) caused by occlusion of a single deep single penetrating artery
  • Defined as: a pure motor stroke, pure sensory stroke, sensorimotor stroke, or ataxic hemiparesis
  • There should be NO: visual field defect, higher cerebral dysfunction, or brainstem dysfunction
  • Best prognosis of all the strokes with 60% of patients alive and independent at 1 year

Investigations

  • ROSIER is a clinical scoring tool based on clinical features and duration - used to recognise stroke in the ER
  • CT head should be performed on arrival to the emergency department to distinguish ischaemic from haemorrhagic stroke
  • CT contrast angiography should also be performed if thrombectomy might be indicated

Management

Acute

Ischaemic stroke
  • Thrombolysis/thrombectomy
    • Alteplase (tissue plasminogen activator) is indicated in patients presenting within 4.5 hours of symptom onset and with no contraindications to thrombolysis
    • Mechanical thrombectomy can be performed in patients with anterior circulation strokes within 6 hours of symptom onset, provided that they have a good baseline functional status and lack of significant early infarction on initial CT scan
    • Mechanical thrombectomy can also be performed in posterior circulation strokes up to 12 hours after onset
  • Aspirin
    • If hyper-acute treatments are not offered, patients should receive aspirin 300 mg orally once daily for two weeks
    • If hyper-acute treatments are offered, aspirin is usually started 24 hours after the treatment following a repeat CT Head that excludes any new haemorrhagic stroke
Haemorrhagic stroke
  • Treatment essentially supportive
Decompressive craniectomy
  • Perform within 48 hours in MCA strokes causing infarction of more than 50% of the MCA territory

Stroke rehabilitation

  • Physiotherapy to help prevent spasticity and contractures, and teach patients how to cope with their current level of function
  • Speech therapy to help with dysphagia
  • Occupational therapist

Secondary prevention interventions

  • Antithrombotic therapy - antiplatelet, anticoagulant
    • Patients should be administered clopidogrel for long-term antiplatelet therapy
    • In patients with ischaemic stroke secondary to atrial fibrillation, however, warfarin or a DOAC is initiated 2 weeks post-stroke
  • Blood pressure control - antihypertensives
  • Cholesterol control - statins
  • Diabetic control
  • Don’t smoke