What are the appropriate evaluation and treatment steps for a patient with sudden or severe limb weakness, considering their age, medical history, and potential underlying conditions such as diabetes, vascular disease, or neurological disorders?

Evaluation and Management of Limb Weakness

For sudden or severe limb weakness, immediately assess for acute limb ischemia by checking for the "6 Ps" (pain, paralysis, paresthesias, pulselessness, pallor, and poikilothermia), and if present with neurological deficits, initiate anticoagulation and proceed directly to emergency revascularization within 4-6 hours without delaying for imaging. 1, 2

Immediate Clinical Assessment

Distinguish vascular emergency from other causes:

• Acute limb ischemia presents with sudden onset of pain, coolness, pallor, absent pulses, sensory loss, and motor weakness—this is a vascular emergency requiring intervention within 4-6 hours to prevent permanent tissue damage and limb loss 1, 2
• The presence of motor deficits or profound sensory loss indicates Rutherford Class IIb (immediately threatened limb) or Class III (irreversible damage), requiring emergency revascularization 1, 2, 3
• Risk factors pointing toward vascular etiology include age ≥65 years, age ≥50 with smoking or diabetes, known atherosclerotic disease (coronary, carotid, renal), atrial fibrillation, chronic kidney disease, or history of claudication 1, 2

Emergency Management for Acute Limb Ischemia

If acute limb ischemia is suspected:

1. Start anticoagulation immediately with intravenous unfractionated heparin (bolus 5000 IU or 70-100 IU/kg, then continuous infusion adjusted by aPTT) to prevent thrombus propagation 1, 3

2. Provide adequate analgesia 1

3. Obtain vascular surgery consultation immediately, even before imaging is complete 2, 4

4. For patients with motor weakness or paralysis: Proceed directly to emergency revascularization within 4-6 hours—imaging should not delay intervention 1, 3

5. For patients without neurological deficits: Obtain CT angiography (CTA) as the preferred initial imaging modality, as it provides rapid, comprehensive anatomic detail of the entire lower extremity arterial circulation including the level of occlusion, degree of atherosclerotic disease, and below-knee vessel patency—all critical for revascularization planning 2, 4

Diagnostic Imaging Strategy

CT angiography is the gold standard initial test for acute limb ischemia because it reveals both the thrombosis and underlying atherosclerotic plaque to plan treatment strategy in a single rapid study 2, 4

Do NOT use these tests as initial evaluation in acute limb ischemia:

• Ankle-brachial index (ABI) only confirms arterial occlusion but provides no information about location, cause, or treatment planning—it is indicated for screening chronic peripheral arterial disease, not acute presentations 2, 4
• Doppler ultrasound is too time-consuming, operator-dependent, limited by heavy calcification, and cannot provide comprehensive anatomic mapping needed for emergency revascularization planning 2, 4
• Echocardiography should not delay revascularization and is not part of the acute workup 2

Revascularization Strategy

Choice of intervention depends on neurological status and imaging findings:

• With neurological deficits: Emergency surgical thrombectomy, mechanical thrombus extraction, or thrombo-aspiration is indicated 1
• Without neurological deficits and symptom duration <14 days: Catheter-directed thrombolysis is the Class I recommendation, with modern combination of intra-arterial thrombolysis and catheter-based clot removal achieving 6-month amputation rates <10% 1, 3
• Endovascular therapy is preferred over open surgery due to reduced morbidity and mortality, especially in patients with severe comorbidities 1, 3
• Systemic (intravenous) thrombolysis has no role in acute limb ischemia treatment 1, 3

Post-Revascularization Management

After successful revascularization:

• Treat the underlying arterial lesion with endovascular therapy or open surgery 1
• Perform four-compartment fasciotomies in patients with long-lasting ischemia to prevent post-reperfusion compartment syndrome 1
• Initiate dual antiplatelet therapy or rivaroxaban 2.5 mg twice daily plus aspirin 100 mg daily to reduce major adverse limb events 2, 3
• Optimize cardiovascular risk factors: high-dose statin for LDL-C target <55 mg/dL, blood pressure control to <130/80 mmHg, and HbA1c <7% in diabetic patients 1, 2

Chronic Limb-Threatening Ischemia

For chronic presentations (>2 weeks duration) with rest pain, ulcers, or gangrene:

• Early recognition and referral to vascular team is mandatory to improve limb salvage 1
• Infra-popliteal revascularization is indicated for limb salvage, with bypass using great saphenous vein as the preferred method 1
• In patients with below-the-knee lesions, angiography including foot runoff should be considered prior to revascularization 1
• In diabetic patients, optimal glycemic control is recommended 1

Non-Vascular Causes of Limb Weakness

If vascular etiology is excluded, consider:

• Functional limb weakness: Characterized by internal inconsistency, positive Hoover's sign, hip abductor sign, drift without pronation, dragging gait, give-way weakness, and co-contraction 5
• Associated with higher rates of childhood sexual abuse (15% vs 5%) and physical abuse (18% vs 7%), medical comorbidity including irritable bowel syndrome (36% vs 18%) and chronic back pain (40% vs 16%), and personality traits of higher neuroticism and lower openness 6
• Misdiagnosis is rare (1%) after long-term follow-up, but symptoms are persistent with complete remission in only 20% at 14-year follow-up 7

Critical Pitfalls to Avoid

• Never delay revascularization for imaging in patients with motor weakness, paralysis, or profound sensory loss—skeletal muscle tolerates ischemia for only 4-6 hours before permanent damage occurs 1, 2, 3
• Do not assume worsening claudication in patients with chronic peripheral arterial disease—acute presentation with diminished pulses represents a vascular emergency requiring immediate intervention 2, 4
• Do not order ABI as the primary investigation in acute limb ischemia—it delays definitive diagnosis and treatment planning 2, 4
• Never use systemic thrombolysis for acute limb ischemia due to poor efficacy and increased adverse events 1, 3