Stroke Overview and Risk Factors

Stroke Overview

• Stroke is a sudden neurological event of vascular origin.
• Stroke is classified into different types:
  • Acute Ischemic Stroke (65%+):
    • Infarction (thrombo-embolic)
  • Haemorrhage (12%):
    • Subarachnoid haemorrhage (6.6%)
    • Intracerebral haemorrhage (5.1%)
  • Transient Ischemic Attack (21%)

Learning Objectives

• Define "stroke."
• Describe the Circle of Willis and extracranial cerebral circulation.
• Understand Transient Ischaemic Attack (TIA).
• Know causes and types of stroke in different age groups.
• Understand stroke prevention, including risk factors.
• Understand principles of acute stroke investigation and management.
• Understand the natural history of acute stroke.

Stroke Risk Factors

• Vessel Wall:
  • Hypertension
  • Smoking
  • Atherosclerosis
  • Hyperlipidaemia
  • Diabetes
• Vessel Lumen:
  • Embolism (Heart disease, impaired cardiac function, CHD, AFib, LVH by ECG, valvular disease)
  • Thrombosis (Haematococrit, Fibrinogen)
  • Other (Race, family history, oral contraceptives, obesity)

Young Stroke (<50)

• All above factors apply
• Additional factors include:
  • Vessel Wall Disease:
    • Large vessel: fibromuscular dysplasia, dissection
    • Small vessel: migraine, vasculitis, drug-induced conditions, sickle cell anaemia, anti-phospholipid syndrome
  • Heart: Congenital heart disease and complications (valve prolapse, patent foramen ovale)

Cerebral Autoregulation

• Cerebral blood flow (CBF): Ischemia thresholds
• Vasodilation occurs.
• CBV in metabolically active tissue = isodense swelling.

Blood Supply to Brain

• Middle cerebral artery (MCA)
• Anterior cerebral artery
• Posterior cerebral artery
• Anterior choroidal artery
• Posterior communicating artery

Collateral Blood Supply

• Good collateral: silent occlusion, infarct extent reduced
• No collateral: massive infarction
• Collateral blocked: propagating thrombus (massive infarction)

Thrombolysis & Clot Retrieval

• Time is brain:
  • < 1.5 hours: 1:4 patients
  • 1.5 – 3.0 hours: 1:7 patients
  • 3.0 – 4.5 hours: 1:14 patients

Endovascular Treatment

• Techniques and procedures used to deal with strokes.
• Rapid endovascular treatment assessment of ischemic stroke.

Small Vessel Disease

• Perforating vessels: end arteries, no collateral, no pressure reduction
• Critical areas: present brain stem(s), design fault. Conditions like Charcot-Bouchard aneurysm
• Lacunar infarction: small infarct but devastating consequences by location

Intracerebral Haemorrhage

• Causes:
  • Hypertension
  • Amyloid
  • Coagulation deficits
  • Aneurysm (AVM)
  • Cavernoma
  • Tumour
  • Drugs (therapeutic & recreational)
  • Trauma
  • Unknown (family history)
• Special Considerations:
  • Cerebellum and Neurosurgeon
  • Venous sinuses
• Summary
  • Hypertension
  • Small vascular malformation (AVM)
  • Sympathomimetic drugs (cocaine/amphetamines)
  • Cerebral amyloid angiopathy (see lecture)
  • Anticoagulants + other bleeding disorders

Subarachnoid Haemorrhage

• Association: Polycystic kidneys
• Causes:
  • Berry (saccular) aneurysm (congenital defect, progressive enlargement)
  • Risk factors: cigarettes, hypertension
• Outcome:
  • Death
  • Coma or alert
  • Survival - rebleed (4-8 days)
  • Death
• Diagnosis:
  • Worst headache in life
  • Neck stiffness
  • Xanthochromia (yellowing of CSF)