What is causing the sensation of heaviness in my whole arm after a recent needle stick injury?

Arm Heaviness After Needle Stick Injury

The sensation of whole arm heaviness following a needle stick injury most likely represents radial nerve injury, which causes weakness of wrist and finger extensors that patients often describe as "heaviness" rather than recognizing it as true weakness. 1, 2, 3

Immediate Clinical Assessment

The key distinction is whether you're experiencing true motor weakness versus subjective heaviness:

• Check for wrist drop: Can you actively extend your wrist against gravity? Inability to do so confirms radial nerve palsy rather than just subjective heaviness 1, 3
• Test finger extension: Attempt to extend your fingers at the knuckles (metacarpophalangeal joints) - radial nerve injury prevents this movement 3, 4
• Assess sensation: Reduced sensation over the dorsum (back) of the hand between thumb and index finger indicates radial nerve involvement 5, 4
• Examine the injection site: Tenderness, swelling, or visible hematoma at the injection site suggests direct nerve trauma or compression from bleeding 2, 5

Why Radial Nerve Injury Causes "Heaviness"

Patients with radial neuropathy frequently describe their arm as "heavy" because:

• The loss of wrist and finger extensor function creates difficulty lifting the hand, which feels subjectively heavy 3, 4
• Denervated muscles lose tone, and the limb feels weighted down during attempted movement 1
• This is distinct from true limb heaviness seen with vascular compromise or stroke 6

Diagnostic Imaging Protocol

Obtain high-resolution ultrasound of the radial nerve from the spiral groove through the forearm to identify the exact site and nature of injury. 1

• Ultrasound should trace the nerve's course to locate compression, hematoma, or direct nerve damage 1, 3
• If ultrasound is equivocal, proceed to MRI with dedicated neurography sequences (diffusion-weighted imaging) for superior soft-tissue detail 1
• Standard imaging is not needed if clinical examination clearly demonstrates isolated radial nerve palsy with obvious injection site trauma 3, 4

Critical Differential Diagnoses to Exclude

Before attributing symptoms solely to radial nerve injury, rule out:

Vascular Compromise

• Unilateral arm swelling with visible venous distension indicates deep vein thrombosis or central venous obstruction, not simple nerve injury 7
• Obtain urgent duplex ultrasound if swelling is present, as upper extremity DVT accounts for 10% of all DVTs and can cause pulmonary embolism 7
• Absent radial pulse or pallor suggests arterial injury requiring immediate CT angiography 6

Central Nervous System Pathology

• Central cord syndrome causes bilateral hand weakness with lower extremity sparing - the presence of isolated unilateral wrist drop without upper motor neuron signs confirms peripheral nerve injury 1
• Stroke would present with upper motor neuron signs (increased tone, hyperreflexia) rather than the flaccid weakness of peripheral nerve injury 6

Immediate Management Strategy

Initiate aggressive physical therapy immediately focusing on wrist and finger extension exercises, with wrist splinting in neutral position (20-30 degrees extension) to prevent contractures and avoid overstretching denervated muscles. 1

Pain Management

• Use topical NSAIDs as first-line treatment for localized pain and inflammation at the injection site 1
• Avoid systemic NSAIDs initially given their inferior safety profile for localized injury 7

Rehabilitation Protocol

• Begin active range of motion exercises immediately to encourage nerve gliding and prevent joint stiffness 8
• Maintain wrist splint continuously except during therapy sessions to prevent overstretching of paralyzed extensors 1, 5
• Continue rehabilitation for at least 3 months, as recovery typically occurs within this timeframe for traumatic radial neuropathy 5, 4

Prognosis and Follow-Up

• Most traumatic radial nerve injuries recover with conservative management within 3-4 months 5, 4
• Reassess at 6-8 weeks: if no improvement in wrist extension strength, consider surgical exploration for nerve decompression 8
• Weakness that persists beyond several months despite splinting and therapy warrants surgical intervention to reduce permanent deficit 8
• Results after surgical decompression are less favorable than carpal tunnel release, with worst outcomes in patients with chronic pain and poor symptom localization 8

Common Pitfalls to Avoid

• Do not dismiss subjective "heaviness" as psychosomatic - patients often cannot articulate motor weakness and describe it as heaviness instead 3, 4
• Do not delay splinting - failure to maintain wrist extension leads to contractures that impair recovery even after nerve regeneration 1, 5
• Do not attribute unilateral arm swelling to nerve injury alone - this indicates venous obstruction requiring urgent evaluation 7
• Do not assume all injection-related nerve injuries are self-limited - space-occupying lesions (hematomas, pseudoaneurysms) may require surgical decompression 2, 8