What causes the feeling of heavy arms and legs?

Differential Diagnosis of Heavy Arms and Legs with Ascending Pattern

The sensation of heavy arms and legs that "works up" (ascends from legs to arms) is most concerning for Guillain-Barré syndrome (GBS), which requires urgent neurological evaluation including spine MRI, CSF analysis, and respiratory monitoring, as approximately 20% of patients develop respiratory failure requiring mechanical ventilation. 1

Immediate Red Flag Assessment

The ascending pattern of weakness with heaviness is the classic presentation of GBS, which typically progresses from legs to arms over hours to days 1. Critical features requiring emergency evaluation include:

• Areflexia or hyporeflexia on examination, which distinguishes GBS from most other causes 1
• Rapid progression of symptoms (reaching maximum disability within 2-4 weeks) 2
• Bilateral involvement affecting both proximal and distal muscle groups 2
• Preceding infection within 6 weeks (Campylobacter jejuni, CMV, Hepatitis E, Mycoplasma, EBV, or Zika) in approximately two-thirds of cases 1

If GBS is suspected, immediate actions include checking vital capacity and negative inspiratory force, monitoring for dysautonomia, and urgent neurology consultation 1. Treatment with IVIG 2 g/kg over 5 days or plasmapheresis should be initiated urgently if GBS is confirmed 1.

Secondary Vascular Considerations

If the heaviness is exertional (occurring with walking/activity) rather than constant and progressive, peripheral artery disease (PAD) must be considered:

• Vascular claudication presents as heaviness, aching, cramping, or tired/fatigued feeling in legs that occurs consistently during walking, does not start at rest, and is relieved within approximately 10 minutes of rest 3, 4
• Symptoms typically affect calf muscles but can involve buttocks, thighs, or feet depending on lesion location 3
• Measure resting ankle-brachial index (ABI) bilaterally - an ABI ≤0.90 confirms PAD diagnosis 4
• If resting ABI is normal but symptoms suggest PAD, perform exercise treadmill ABI test 4

Key distinction: PAD symptoms are induced by exercise and relieved by rest, whereas neurological causes like GBS produce constant or progressive symptoms unrelated to activity 3, 1.

Spinal Cord and Nerve Root Pathology

Bilateral hand involvement with unilateral foot weakness suggests a cervical cord lesion at C5-C7 level affecting both upper extremities and descending motor tracts 1. However, if symptoms are truly ascending from legs to arms, this pattern is less consistent with compressive myelopathy.

Spinal stenosis (neurogenic claudication) can cause bilateral leg heaviness but:

• Symptoms may improve with walking or lumbar spine flexion and worsen with standing upright or extension 4
• Relief can take a long time to recover, unlike vascular claudication 3
• Typically does not ascend to involve arms unless there is concurrent cervical stenosis 3

Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)

CIDP should be considered if symptoms have been progressive or relapsing over at least 2 months (unlike GBS which reaches maximum disability within 2-4 weeks) 2:

• Affects both proximal and distal regions symmetrically 2
• Distal paresthesias or sensory loss can progress proximally 2
• Progressive weakness typically starts in legs and potentially spreads to arms 2

Metabolic and Systemic Causes

Uremic neuropathy from renal insufficiency should be excluded with creatinine, eGFR, and urinalysis 1. This typically presents with length-dependent symptoms (feet before hands) rather than true ascending pattern.

Polymyalgia-like syndrome from immune checkpoint inhibitors can cause severe myalgia in proximal upper and lower extremities with severe fatigue, but patients have pain without true weakness and CK levels are normal 3.

Diagnostic Algorithm

1. Immediate assessment: Check reflexes, vital capacity, and negative inspiratory force 1
2. If areflexic with ascending weakness: Urgent MRI spine, CSF analysis, admit for respiratory monitoring 1
3. If exertional symptoms: Measure bilateral resting ABI; if ≤0.90, diagnose PAD 4
4. If normal ABI with exertional symptoms: Consider exercise ABI test or evaluate for spinal stenosis 4
5. If chronic progressive course (>2 months): Consider CIDP with nerve conduction studies 2
6. Check renal function in all patients to exclude uremic neuropathy 1

Critical Pitfalls to Avoid

• Do not dismiss ascending bilateral weakness as musculoskeletal - this pattern demands urgent neurological evaluation for GBS 1
• Do not confuse vascular claudication with neurogenic claudication - vascular symptoms resolve within 10 minutes of rest, neurogenic symptoms take much longer 3, 4
• Do not assume symmetric symptoms exclude serious pathology - both GBS and CIDP can present with relatively symmetric involvement 1, 2
• Do not delay respiratory monitoring in suspected GBS - respiratory failure can develop rapidly and is the leading cause of morbidity 1