Epidemiology of Stroke

Stroke Epidemiology

• Stroke is the second most common cause of morbidity worldwide, after myocardial infarction.
• It is the leading cause of acquired disability.
• Risk factors for ischemic stroke largely mirror those for atherosclerosis and include:
  • Age
  • Gender
  • Family history
  • Smoking
  • Hypertension
  • Hypercholesterolemia
  • Diabetes mellitus

Clinical Presentation

• An ischemic stroke typically presents with rapid onset neurological deficit, determined by the area of the brain involved.
• Symptoms evolve over hours and may worsen or improve depending on the fate of the ischemic penumbra.
• The vascular territory affected will determine the exact symptoms and clinical behavior of the lesion.

Pathology

• Interruption of blood flow through an intracranial artery leads to deprivation of oxygen and glucose in the supplied vascular territory.
• This initiates a cascade of events at a cellular level, which, if circulation is not re-established in time, will lead to cell death, mostly through liquefactive necrosis.
• The mechanism of vessel obstruction is important in addressing therapeutic maneuvers to both attempt to reverse or minimize the effects and to prevent future infarcts.

Mechanisms of Vessel Obstruction

• Embolism
  • Cardiac embolism
  • Paradoxical embolism
  • Atherosclerotic embolism
  • Fat embolism
  • Air embolism
• Thrombosis
  • Perforator thrombosis: lacunar infarct
  • Acute plaque rupture with overlying thrombosis
• Arterial dissection
• Global cerebral hypoxia (as seen in drowning or asphyxiation)

Radiographic Features

• Non-contrast CT of the brain remains the mainstay of imaging in the setting of an acute stroke.
• It is fast, inexpensive, and readily available.
• Its main limitation is the limited sensitivity in the acute setting.

CT Signs

• Hyperdense segment of a vessel, representing direct visualization of the intravascular thrombus/embolus.
• Hypoattenuation and swelling become more marked with time, resulting in a significant mass effect.
• CT fogging phenomenon: elevation of the attenuation of the cortex due to small amounts of cortical petechial hemorrhages.
• Later, the residual swelling passes, and gliosis sets in, eventually appearing as a region of low density with a negative mass effect.
• Cortical mineralization can also sometimes be seen, appearing hyperdense.

CT Perfusion

• Allows both the core of the infarct and the surrounding penumbra to be identified.
• it identifies the core of the infarct (that part destined to never recover regardless of reperfusion) and the surrounding penumbra (the region which although ischemic has yet to go on to infarct and can be potentially salvaged).
• It demonstrates early evidence of associated crossed cerebellar diaschisis.

CT Angiography

• May identify thrombus within an intracranial vessel, and may guide intra-arterial thrombolysis or clot retrieval.
• Evaluates the carotid and vertebral arteries in the neck.
• maybe necessary prior to thrombolysis in pediatric stroke cases.
• Assesses collateral vessels using single-phase CTA.