ISCHEMIC STROKE / ETIOLOGY

Created 02/12/2022, last revision 04/09/2023

• lacunar stroke (lacunar cerebral infarct – LACI) is defined as a small subcortical lesion ≤ 1.5 cm in diameter that is caused by the occlusion of small penetrating arteries
  • penetrating arteries arise at sharp angles from larger vessels and are, therefore, anatomically prone to stenosis and occlusion
  • the term “lacune” was first described in the late 19th and early 20th centuries – it usually describes a small, chronic cavity that represents the healed phase of a lacunar infarct
  • etiology of the lacunar infarct is not necessarily of arteriolopathic origin ⇒ various mechanisms can cause occlusion!
  • the most frequently affected structures are:
    • basal ganglia (globus pallidus, putamen, thalamus, and caudate)
    • pons
    • subcortical white matter structures (internal capsule and corona radiata)
• lacunar stroke syndrome (LACS) is a clinical manifestation of lacunar stroke; the most common are:
  • pure motor hemiparesis
  • pure sensory stroke
  • sensorimotor stroke
  • ataxic hemiparesis
  • dysarthria-clumsy hand syndrome

• lacunar infarcts usually cause symptoms within minutes but may also exhibit a more gradual progression
• symptoms usually do not include cortical signs ( agnosia, aphasia, neglect, apraxia, or hemianopsia)
  • cortical functions must be tested to differentiate the MCA stroke and the subcortical stroke (thalamus, internal capsule)
• most common syndromes are:
  • pure motor hemiparesis
  • pure sensory stroke (unilateral numbness of the face, arm, and leg; affecting all sensory modalities)
  • ataxic hemiparesis (unilateral limb ataxia that is disproportionate to the strength/motor deficit)
  • sensorimotor stroke (unilateral weakness and numbness)
  • dysarthria-clumsy hand syndrome (unilateral facial weakness, dysarthria, dysphagia, and dysmetria/clumsiness in one upper extremity)

• brain imaging (CT/MRI)
  • excludes hemorrhage
  • DWI is more sensitive in detecting acute infarcts compared to other MRI sequences or CT scans
  • in the acute phase, CT or even MRI may be negative; later, a small noncortical infarct may be visible
• vascular imaging (CTA/MRA)
  • excludes large vessel occlusion/stenosis
  • small perforating arteries are difficult to visualize effectively with CTA and MRA
  • high-resolution MRI can detect the ostial microatheroma in penetrating artery; larger lesions are found in such cases (Sun, 2018)
• the definitive diagnosis is established by a combination of a typical lacunar syndrome + negative findings on CTA/MRA + small, noncortical infarct visible on CT/MRI
  • history of longstanding diabetes, hypertension, and hyperlipidemia is typical
    
  • such a stroke is classified as TOAST 3
• for young patients without traditional risk factors, further evaluation may be necessary to exclude an embolic source