Subacute Lacunar Infarct: Definition and Clinical Implications
A subacute lacunar infarct is a small subcortical stroke measuring less than 1.5 cm in diameter that occurs due to occlusion of a single penetrating artery, typically in the subacute phase of evolution (between 24 hours and several weeks after onset). 1
Characteristics of Lacunar Infarcts
- Lacunar infarcts are subcortical strokes measuring <1.5 cm in diameter on CT or MRI without evidence of a concomitant cortical infarct 1
- They account for approximately 25% of all ischemic strokes 2
- Most lacunar infarcts are due to small vessel disease affecting penetrating arteries deep in the brain or brain stem 1
- They are strongly associated with hypertension and diabetes mellitus as major risk factors 2
Clinical Presentation
- Patients typically present with one of the classical lacunar syndromes 2:
- Pure motor hemiparesis
- Pure sensory syndrome
- Sensorimotor stroke
- Ataxic hemiparesis
- Dysarthria-clumsy hand syndrome
- Less commonly, patients may present with atypical lacunar syndromes 2
Pathophysiology
- The primary mechanism is occlusion of a single penetrating artery 2
- Unlike other stroke subtypes, lacunar infarcts are generally not caused by atherosclerosis but rather by a distinct arteriopathy of small vessels 1
- While traditionally attributed to small vessel disease, some lacunar infarcts may have embolic origins in a small percentage of cases 3
Prognosis
- Lacunar infarcts show a paradoxical clinical course 2:
- Favorable short-term prognosis with low early mortality and reduced functional disability at hospital discharge
- Increased risk of death, stroke recurrence, and dementia in the mid and long term
- Among stroke subtypes, patients with small-artery occlusion have the highest survival rate (85% at 2 years) compared to other stroke subtypes 1
- Despite better survival rates, lacunar infarcts should not be considered benign due to their association with cognitive decline and dementia risk 4, 5
Management Considerations
- Acute treatment response to intravenous thrombolysis appears similar to other ischemic stroke subtypes 4
- Secondary prevention strategies include 2, 4:
- Antiplatelet therapy (single agent)
- Careful blood pressure control
- Statin therapy
- Modification of lifestyle risk factors
- Escalation of antithrombotic therapy beyond single antiplatelet agents has not shown benefit and increases bleeding risk 6
Clinical Implications
- Asymptomatic progression of small vessel disease is a typical feature of lacunar infarcts 2
- Silent small vessel disease in the brain at the time of index stroke has significant prognostic implications 4
- Risk of recurrent stroke after lacunar infarct is similar to that of most other stroke subtypes, despite better initial survival 5
Diagnostic Considerations
- Diagnosis requires neuroimaging (CT or MRI) showing a small (<1.5 cm) subcortical infarct 1
- Potential sources of cardioembolism and ipsilateral large-artery stenosis should be excluded to confirm the diagnosis of lacunar stroke 1
- Up to one-third of apparent lacunar infarcts may have causes other than penetrating small vessel disease 4