Can instability while walking in an adult or elderly patient with vascular risk factors be indicative of a Partial Anterior Circulation Infarct (PACI) or Lacunar Infarct (LACI) stroke?

Instability While Walking: Stroke Classification

Instability while walking alone is insufficient to classify a stroke as PACI or LACI—this symptom requires urgent neuroimaging and comprehensive clinical assessment to determine stroke subtype, as isolated gait instability can occur with lacunar infarcts (particularly ataxic hemiparesis syndrome), posterior circulation infarcts, or cortical strokes depending on associated neurological deficits. 1, 2, 3

Clinical Approach to Classification

Key Distinguishing Features

Lacunar Infarct (LACI) Presentation:

• Gait instability in LACI typically manifests as one of five classical lacunar syndromes, most commonly ataxic hemiparesis (combination of weakness and incoordination on the same side) 4, 2
• Pure motor hemiparesis, pure sensory syndrome, sensorimotor stroke, or dysarthria-clumsy hand syndrome without cortical signs 1, 2
• Lesions are subcortical, <1.5 cm, located in basal ganglia, brainstem, or deep white matter 1, 2, 3
• Critically, LACI should NOT have: cortical signs (aphasia, neglect, visual field defects, higher cortical dysfunction) 1, 2

Partial Anterior Circulation Infarct (PACI) Presentation:

• Requires at least 2 of 3 features: motor/sensory deficit, higher cortical dysfunction (aphasia, neglect), or homonymous hemianopia 5, 6
• Gait instability would be accompanied by cortical signs such as facial numbness with facial weakness, which indicates cortical involvement 1
• Middle cerebral artery velocity abnormalities present in 29% of PACI cases 5

Posterior Circulation Infarct (POCI) Considerations:

• Ataxia is present in 68-86% of patients with brainstem stroke 4
• Basilar or vertebral artery abnormalities on vascular imaging 5
• May present with isolated gait ataxia, vertigo, diplopia, or crossed sensory/motor findings 4

Critical Diagnostic Algorithm

Step 1: Assess for Cortical Signs

• If cortical signs present (aphasia, neglect, visual field defects, facial numbness with weakness): NOT lacunar—consider PACI or total anterior circulation infarct 1, 6
• If pure motor/sensory syndrome without cortical signs: Consider LACI but imaging confirmation mandatory 2, 3

Step 2: Mandatory Imaging Workup

• Non-contrast CT head immediately to exclude hemorrhage 1, 3
• Vascular imaging (CTA or MRA) urgently to exclude large vessel occlusion, even when LACI suspected clinically 3
• MRI superior to CT for detecting acute cortical infarcts and distinguishing from lacunar infarcts 1
• Confirm infarct size <1.5 cm and subcortical location for LACI diagnosis 2, 3

Step 3: Exclude Alternative Etiologies

• Transthoracic echocardiography and extended cardiac monitoring to exclude cardioembolic source 1, 3
• Carotid imaging within 48 hours to exclude >50% stenosis of ipsilateral large artery 1, 3
• A patient with atrial fibrillation and small subcortical infarct requires anticoagulation, not just antiplatelet therapy—misclassification has direct therapeutic consequences 3

Common Pitfalls and Caveats

Misclassification Risks

• Only 58% of clinical LACI diagnoses are confirmed as small-artery disease on comprehensive workup; 29% are actually due to large-artery atherosclerosis 6
• Only 68% of patients with clinical LACI syndrome have small subcortical infarction on imaging—the remainder have alternative pathology 6
• Clinical syndrome alone has sensitivity of only 33% for LACI when compared to CT classification 7

Ataxia-Specific Considerations

• Ataxia typically improves during acute rehabilitation and has better prognosis without concurrent hemiparesis 4
• Postural training and task-oriented therapy should be initiated for rehabilitation of ataxia 4
• Balance training programs are Class I recommendation for stroke patients with poor balance and fall risk 4

Fall Risk Assessment

• Stroke patients have fall rates as high as 50% in community-dwelling survivors 4
• Gait instability and trunk instability significantly increase fall risk 4
• All stroke patients should be evaluated for balance, balance confidence, and fall risk (Class I recommendation) 4
• Assistive devices (cane, walker) improve ambulatory function and should be prescribed when appropriate 4

Prognostic Implications

If confirmed LACI:

• Highest survival rate among stroke subtypes (85% at 2 years) 2, 3
• Lowest 90-day mortality (3.3%) 2
• However, long-term risk of stroke recurrence and dementia remains elevated 2

If PACI:

• 13% recurrence rate within 2 years, with one-third progressing to more severe total anterior circulation infarct 8
• Etiology equally divided between cardioembolism and large-artery atherosclerosis 6