What are the next steps for a patient experiencing bilateral lower extremity (BLE) weakness, leg heaviness, and dizziness for 2 weeks?

Immediate Diagnostic Workup for Bilateral Lower Extremity Weakness with Dizziness

This patient requires urgent hospitalization and immediate evaluation for potentially life-threatening neuromuscular conditions, particularly Guillain-Barré syndrome (GBS) or chronic inflammatory demyelinating polyneuropathy (CIDP), given the 2-week duration of progressive bilateral leg weakness. 1

Critical First Steps (Within Hours)

Neuromuscular Emergency Assessment

• Hospitalize immediately for close monitoring of respiratory function, as GBS can rapidly progress to respiratory failure requiring mechanical ventilation 1
• Assess respiratory capacity with bedside spirometry (forced vital capacity, negative inspiratory force) to detect early respiratory compromise 1
• Perform urgent cerebrospinal fluid (CSF) analysis looking for albuminocytologic dissociation (elevated protein with normal white blood cell count), which supports GBS or CIDP diagnosis 1
• Obtain nerve conduction studies and electromyography (NCS/EMG) to identify demyelinating patterns characteristic of GBS or CIDP 1

Metabolic Emergency Evaluation

• Obtain immediate serum potassium level and electrocardiogram (ECG), as bilateral lower extremity paralysis with weakness can indicate thyrotoxic hypokalemic periodic paralysis or other electrolyte emergencies 2, 3
• Check thyroid function tests (TSH, free T4, free T3) if hypokalemia is present, as thyrotoxic periodic paralysis presents with acute bilateral leg weakness and is reversible with treatment 3
• The ECG will show characteristic changes with hypokalemia (U waves, flattened T waves, prolonged QT) that immediately point to metabolic etiology 2

Vascular Assessment

Peripheral Arterial Disease Evaluation

• Obtain resting ankle-brachial index (ABI) with segmental pressures and pulse volume recordings as the initial noninvasive test 4, 1
• Interpret ABI results: ≤0.90 confirms PAD; 0.91-0.99 is borderline; 1.00-1.40 is normal; >1.40 indicates noncompressible vessels requiring toe-brachial index (TBI) 4, 1
• Perform comprehensive vascular examination including palpation of femoral, popliteal, dorsalis pedis, and posterior tibial pulses, auscultation for femoral bruits, and inspection of legs and feet 4

However, PAD typically presents with exertional leg symptoms (claudication) that improve with rest, not constant heaviness and weakness at rest. 4 The 2-week duration of constant symptoms makes acute limb ischemia unlikely, as ALI requires evaluation within 4-6 hours due to muscle ischemia tolerance 4

Orthostatic Hypotension Assessment

Autonomic Dysfunction Evaluation

• Measure orthostatic vital signs (blood pressure and heart rate supine, then at 1 and 3 minutes after standing) 1
• Orthostatic hypotension is defined as systolic BP drop ≥20 mmHg or diastolic drop ≥10 mmHg, which can cause dizziness and perceived leg weakness 1
• This is particularly important given the patient's complaint of dizziness accompanying the leg symptoms 1

Diabetic/Metabolic Neuropathy Assessment (If Applicable)

• Perform comprehensive foot and neurological examination if diabetes or other neuropathy risk factors are present 1
• Use 10-gram monofilament testing at multiple sites on both feet to assess for loss of protective sensation 1
• Check hemoglobin A1c, vitamin B12, and consider other metabolic causes of peripheral neuropathy 1

Diagnostic Algorithm Priority

The timing and pattern of symptoms guide the differential:

1. Progressive bilateral weakness over 2 weeks = neuromuscular emergency first (GBS/CIDP) 1
2. Acute onset with abnormal ECG = metabolic emergency (hypokalemia, thyrotoxicosis) 2, 3
3. Exertional leg heaviness with normal rest = vascular disease (PAD) 4
4. Dizziness with positional component = orthostatic hypotension 1

Critical Pitfalls to Avoid

• Do not discharge this patient without ruling out GBS, as respiratory failure can develop rapidly and is the leading cause of death in GBS 1
• Do not assume PAD based solely on "heavy legs" without confirming exertional pattern and obtaining ABI, as many conditions mimic PAD symptoms 4, 5
• Do not delay CSF analysis and NCS/EMG if neuromuscular disease is suspected, as early treatment with IVIG or plasma exchange improves outcomes in GBS/CIDP 1
• Do not miss hypokalemia by failing to check basic electrolytes and ECG, as this is immediately reversible and potentially fatal if untreated 2, 3