What could be causing arm heaviness and weakness in a patient?

Arm Heaviness and Weakness: Differential Diagnosis and Urgent Evaluation

Immediate Life-Threatening Causes to Exclude First

Arm heaviness and weakness requires immediate evaluation for acute coronary syndrome (ACS), stroke/TIA, and vascular access steal syndrome, as these conditions can rapidly progress to permanent disability or death if not recognized within minutes to hours.

Acute Coronary Syndrome (Cardiac Ischemia)

• Arm pain, heaviness, and weakness are recognized presenting symptoms of ACS, particularly in women, who present with atypical symptoms more frequently than men 1, 2, 3.
• Bilateral arm symptoms with associated nausea, diaphoresis, or chest pressure represent high-risk ACS presentation requiring immediate ECG within 10 minutes and cardiac troponin measurement 2, 4.
• Left arm pain with radiation pattern is a cardinal feature of unstable angina or NSTEMI, with women experiencing arm symptoms in 61.9% of MI cases versus 54.8% in men 3, 4.
• Obtain 12-lead ECG within 10 minutes of presentation and measure high-sensitivity cardiac troponin immediately in any patient with arm heaviness plus cardiovascular risk factors (age >50, diabetes, hypertension, hyperlipidemia, smoking, family history) 2, 3.

Stroke or Transient Ischemic Attack (TIA)

• Unilateral arm weakness (with or without face/leg involvement) represents VERY HIGH risk for stroke, requiring immediate emergency department evaluation within 48 hours of symptom onset 1.
• Transient, fluctuating, or persistent unilateral weakness places patients at highest risk for first or recurrent stroke, with 7-day stroke risk as high as 36% in patients with multiple risk factors 1.
• Urgent brain imaging (CT or MRI) and noninvasive vascular imaging (CTA or MRA from aortic arch to vertex) must be completed within 24 hours 1.
• Patients presenting between 48 hours and 2 weeks with unilateral arm weakness require comprehensive evaluation by stroke specialist within 24 hours 1.

Vascular Access Steal Syndrome (Dialysis Patients)

• Arm heaviness, coldness, pain, and weakness in dialysis patients with arteriovenous fistula (AVF) or graft indicates steal syndrome requiring emergent vascular surgery referral 1.
• Symptomatic peripheral ischemia occurs in 1-4% of AVF patients, with milder symptoms (coldness, pain during dialysis) occurring in up to 10% 1.
• Monomelic ischemic neuropathy presents with acute global muscle pain, weakness, and warm hand with palpable pulses starting within first hour after AVF creation—immediate closure of AVF is mandatory 1.
• Staging system: Stage I (pale/blue/cold hand without pain), Stage II (pain during exercise/dialysis), Stage III (pain at rest), Stage IV (ulcers/necrosis/gangrene) 1.

Neuromuscular Causes Requiring Urgent Evaluation

Cervical Spinal Cord Injury Without Fracture/Dislocation

• Central cord syndrome presents with arm weakness and heaviness greater than leg weakness, often following ground-level falls in patients with pre-existing cervical stenosis 1.
• Patients may experience numbness and burning dysesthesias in arms with decreased hand strength (finger flexors/abductors most affected) 1.
• MRI showing spinal cord signal change from C3-C7 with congenital or degenerative canal narrowing confirms diagnosis 1.
• Early surgical decompression within 48 hours may worsen neurologic outcomes in spinal cord injury without fracture/dislocation—conservative management often preferred initially 1.

Brachial Plexus Compression (Thoracic Outlet Syndrome)

• Neurological dominant thoracic outlet syndrome (nTOS) causes chronic arm and hand paresthesia, numbness, or weakness from brachial plexus compression 1.
• Compression occurs at three spaces: costoclavicular triangle (venous symptoms dominant), interscalene triangle (neurological/arterial symptoms), or pectoralis minor space 1, 5.
• Symptoms include shoulder, neck, chest, and arm pain with paresthesia and weakness in arm and hand, often related to repetitive overhead activities 1, 5.
• Diagnosis requires detailed occupational/activity history, physical examination with provocative maneuvers, and imaging (CT/MRI in neutral and stressed positions) to identify anatomic compression 1, 5.

Peripheral Nerve or Neuromuscular Junction Disorders

• Acute onset bilateral arm and leg weakness requires immediate evaluation for Guillain-Barré syndrome, myasthenia gravis, or thyrotoxic periodic paralysis 6, 7, 8.
• Thyrotoxic hypokalemic periodic paralysis presents with sudden-onset severe lower extremity weakness progressing to trunk and arms, with hypokalemia (K+ <2.5 mEq/L) and hyperthyroidism 8.
• Check serum potassium, thyroid function tests, and creatine kinase in patients with acute bilateral weakness 8.

Musculoskeletal and Inflammatory Causes

Rotator Cuff Dysfunction and Shoulder Impingement

• Rotator cuff injury in overhead athletes causes pain during throwing at release/deceleration phases, with decreased velocity, precision, and focal weakness during abduction with rotation 1.
• Secondary shoulder impingement from rotator cuff weakness and ligamentous laxity causes anterolateral shoulder pain with arm heaviness during overhead activities 1.
• Scapular dyskinesis (poor coordination of scapular upward rotation and posterior tilting) contributes to rotator cuff injury and arm weakness 1.

Immune Checkpoint Inhibitor-Related Myositis

• Patients on immune checkpoint inhibitors (anti-PD-1/PD-L1, anti-CTLA-4) can develop severe myositis with proximal arm and leg weakness, myalgia, and elevated creatine kinase 1.
• Polymyalgia-like syndrome causes severe myalgia in proximal upper/lower extremities with severe fatigue but without true weakness (normal CK, elevated inflammatory markers) 1.
• Myositis presents with weakness (not just pain) in proximal extremities, elevated CK, and requires EMG and MRI for diagnosis—can be fatal if myocarditis develops 1.

Diagnostic Algorithm for Arm Heaviness and Weakness

Step 1: Immediate Triage (Within 10 Minutes)

1. Obtain vital signs and 12-lead ECG immediately 2, 4.
2. Assess for unilateral versus bilateral symptoms 1.
3. Check for associated symptoms: chest pain/pressure, jaw pain, nausea, diaphoresis (suggests ACS) 2, 3, 4; facial weakness, speech disturbance (suggests stroke) 1; dialysis access present (suggests steal syndrome) 1.

Step 2: Risk Stratification and Initial Testing

• If cardiovascular risk factors present OR associated cardiac symptoms: Measure cardiac troponin immediately, repeat at 6 hours if initial negative 2, 4.
• If unilateral arm weakness within 48 hours: Immediate CT/MRI brain and CTA/MRA aortic arch to vertex 1.
• If dialysis patient with AVF/AVG: Measure digital blood pressure, perform Doppler ultrasound, assess for hand ischemia staging 1.
• If acute bilateral weakness: Check serum potassium, thyroid function, creatine kinase, consider EMG/nerve conduction studies 6, 7, 8.

Step 3: Disposition Based on Findings

• STEMI on ECG: Activate catheterization lab for primary PCI (door-to-balloon <90 minutes) or thrombolytics if PCI unavailable 2, 4.
• Stroke/TIA confirmed: Admit to stroke unit, initiate antiplatelet therapy, consider thrombolysis if within window 1.
• Steal syndrome Stage III-IV: Emergent vascular surgery consultation for possible AVF ligation 1.
• Spinal cord injury without fracture: Conservative management preferred initially; avoid early decompression unless progressive neurologic decline 1.

Critical Pitfalls to Avoid

• Never dismiss bilateral arm heaviness as musculoskeletal without excluding cardiac causes first, especially in women over 50, diabetics, and patients with cardiovascular risk factors 2, 3, 4.
• Do not assume normal vital signs exclude ACS—patients with unstable angina or NSTEMI frequently maintain normal blood pressure and pulse 4.
• Avoid relying on nitroglycerin response as diagnostic for ACS, as esophageal spasm and other conditions may also respond 2, 3.
• Do not delay emergency evaluation for cost concerns—EMTALA requires stabilizing treatment regardless of ability to pay, and cost of delayed ACS/stroke diagnosis far exceeds evaluation cost 2.
• Never perform early surgical decompression (<48 hours) in spinal cord injury without fracture/dislocation, as this may worsen neurologic outcomes 1.
• In dialysis patients, do not delay vascular surgery referral for fingertip necrosis or Stage III-IV steal syndrome, as progression to gangrene and amputation can occur rapidly 1.