Cryptogenic Stroke

Overview

• Acute ischemic stroke is an episode of acute neurological dysfunction caused by focal cerebral, spinal, or retinal infarction.
• Acute intracerebral hemorrhage is a stroke presenting with rapidly developing clinical signs of neurological dysfunction attributable to a focal collection of blood within the brain parenchyma or ventricular system that is not caused by trauma
• Acute subarachnoid hemorrhage is a stroke presenting with rapidly developing signs of neurological dysfunction and/or headache because of bleeding into the subarachnoid space (the space between the arachnoid membrane and the pia mater of the brain or spinal cord), which is not caused by trauma
• Strokes are generally classified as ischemic or hemorrhagic:
  • ischemic strokes (80%-87% of strokes) are caused by large artery atherosclerosis (embolus or thrombosis), small vessel occlusion (lacunar), cardioembolism (often from atrial fibrillation), hypercoagulability (antiphospholipid antibody syndrome), and arterial dissection among other causes
  • hemorrhagic stroke are typically due to intracerebral hemorrhage or subarachnoid hemorrhage
    • most common mechanism of intracerebral hemorrhage is hypertensive small-vessel disease, causing small lipohyalinotic Charcot-Bouchard microaneurysms that rupture
    • most subarachnoid hemorrhages are caused by rupture of saccular aneurysms
• Cryptogenic stroke, or ischemic stroke of unknown cause, after a thorough work-up is completed, is reported to occur in up to 30% of patients with ischemic stroke in United States.
• Implicated mechanisms in patients with cryptogenic stroke include
  • occult paroxysmal atrial fibrillation
  • substenotic atherosclerosis
  • hypercoagulability
  • paradoxical embolism through patent foramen ovale (PFO)
  • see Patent foramen ovale (PFO) topic for details
• To evaluate potential causes of ischemia in patients with unknown stroke mechanism after initial testing, consider:
  • magnetic resonance imaging (MRI)
  • vascular imaging, such as
    • magnetic resonance angiography (MRA) of head and neck
    • computed tomographic angiography (CTA)
  • cardiac evaluation, including
    • transesophageal echocardiography (TEE), cardiac magnetic resonance imaging (CMR), or other imaging
    • noninvasive monitoring, such as electrocardiography, Holter monitor, and telemetry (inpatient continuous and mobile continuous outpatient)
  • hematologic and serological evaluation to assess for hypercoagulability
• After exclusion of other potential causes of cryptogenic stroke, consider:
  • evaluation for malignancy
  • appropriate testing to evaluate for infectious, autoimmune, and inflammatory causes of stroke