What is causing the heaviness in a patient's arm, given their history of improved wrist function and residual weakness, fatigue, or nerve damage?

Differential Diagnosis of Whole Arm Heaviness

The most likely cause of whole arm heaviness in a patient with improved wrist function but residual weakness and fatigue is peripheral nerve injury with incomplete recovery, specifically affecting the brachial plexus or a major nerve trunk (median, ulnar, or radial nerve), resulting in both motor weakness and central activation failure. 1, 2

Primary Diagnostic Considerations

Nerve Injury with Incomplete Recovery

• Residual weakness and fatigue following nerve injury commonly persist even after partial functional recovery, with patients experiencing a sensation of heaviness due to both peripheral nerve dysfunction and reduced central motor activation 1, 2
• Nerve compression or injury causes a 23-42% reduction in strength and associated fatigue that correlates directly with the degree of nerve damage 3
• Central activation failure occurs in 36-41% of neuromuscular patients even at rest, compared to only 12% in healthy controls, contributing significantly to the sensation of heaviness and weakness 2

Specific Nerve Pathologies to Consider

Median Nerve Compression:

• Compression at the wrist from glycogen deposition in the carpal tunnel can cause progressive weakness and heaviness 1
• Direct compression from repetitive activities (weight-bearing, lifting) can cause recurrent median neuropathy with thenar atrophy and localized weakness 4
• Wrist splints during sleep may prevent excessive flexion that exacerbates compression 1

Ulnar Nerve Entrapment:

• Conduction block at the elbow produces 42% reduction in strength and 23% reduction in fatigue resistance 3
• The degree of weakness and fatigue correlates strongly (r=0.74 for strength, r=0.60 for fatigue) with the extent of conduction block 3

Musculocutaneous Nerve Injury:

• Entrapment or stretching where the nerve passes through coracobrachialis causes weakness and loss of biceps contour 5
• Related to heavy physical activity or strenuous exercise 5
• May leave residual weakness even after partial recovery 5

Brachial Plexus Dysfunction:

• Provokes both local symptoms (arm fatigue, heaviness, paresthesias) and systemic symptoms (generalized fatigue, lightheadedness) in 97% of patients within 20 seconds of arms-overhead positioning 6
• Particularly common in patients with chronic fatigue conditions and orthostatic intolerance 6
• Associated with joint hypermobility in 58% of cases 6

Critical Diagnostic Workup

Initial Evaluation

• Obtain plain radiographs of the elbow first to identify intra-articular bodies, heterotopic ossification, osteochondral lesions, or post-traumatic changes 7
• Perform electrodiagnostic studies (EMG/nerve conduction studies) to confirm diagnosis and localize compression site 7
• Reserve MRI without contrast (including T2-weighted MR neurography) for cases where initial workup is nondiagnostic or surgical planning is needed 7

Physical Examination Findings

• Assess for focal weakness with decreased range of motion during abduction with external or internal rotation 1
• Check for sensory deficits: decreased pain perception and temperature sensation in painful areas 1
• Evaluate for autonomic involvement: postural hypotension, bladder disturbances, constipation 1
• Test for central activation failure by assessing effort-dependent weakness that improves with encouragement 2

Red Flags Requiring Urgent Evaluation

• Night pain or pain at rest suggests inflammatory or neoplastic processes rather than simple compression 7
• Acute onset with warm hand and palpable pulses in dialysis patients suggests monomelic ischemic neuropathy requiring immediate AVF closure 1, 7
• Progressive weakness with muscle atrophy indicates ongoing nerve damage 4

Management Approach

Conservative Management

• Complete rest from aggravating activities until asymptomatic 1
• Rehabilitation emphasizing rotator cuff and scapular stabilizer strengthening, proper mechanics, and range of motion restoration 1
• Graded, supervised exercise programs reduce fatigue in 60-80% of patients with residual neurological complaints 1
• Wrist splinting at night for median nerve compression 1

Monitoring for Complications

• Avoid overwork during exercise as it can cause increased fatigue 1
• Monitor for progression of weakness or development of muscle atrophy 4
• Serial strength and endurance assessments to guide individualized exercise programs 1

When to Escalate Care

• Refer to vascular surgeon immediately if ischemic manifestations threaten limb viability 1
• Consider neurologist consultation if asymmetric pattern of symptoms or normal clinical examination despite complaints 1
• Surgical evaluation if conservative management fails after 1-3 months 1

Common Pitfalls to Avoid

• Do not assume weakness is purely peripheral—central activation failure contributes significantly to perceived heaviness and fatigue 2
• Do not delay electrodiagnostic studies when clinical suspicion is high, as early diagnosis prevents permanent disability 4
• Do not overlook autonomic symptoms (constipation, postural hypotension) that indicate small fiber involvement 1
• Fear of physical activity or fear of damaging tissue may contribute to reduced central activation and should be addressed through patient education 2