What are the differential diagnoses for a patient presenting with severe right-sided neck pain radiating to the arm?

Differential Diagnosis of Right-Sided Severe Neck Pain Radiating to Arm

The most likely diagnosis is cervical radiculopathy from nerve root compression, typically caused by disc herniation or degenerative spondylosis, but you must systematically rule out serious "red flag" conditions including infection, malignancy, myelopathy, and vascular causes before attributing symptoms to mechanical causes. 1, 2

Primary Mechanical Causes (Most Common)

Cervical Radiculopathy

• Nerve root compression from herniated disc or osteophytes is the primary cause, presenting with unilateral neck pain radiating to the arm in a dermatomal distribution with sensory or motor deficits 3, 4
• Annual incidence is approximately 83 per 100,000 persons, most commonly affecting C5-C6 and C7 nerve roots 1, 2
• Compression occurs from soft disc herniation, hard disc (facet or uncovertebral joint spondylarthrosis), or combination of both 3, 4
• Patients describe "electric" quality neuropathic pain with specific dermatomal distribution, accompanied by reflex changes 2
• 75-90% of cases resolve with conservative management, making this the most favorable prognosis 3, 5

Cervical Spondylosis and Degenerative Disc Disease

• Extremely common, affecting 53.9% of individuals aged 18-97, with prevalence increasing with age 3
• Facet joint arthropathy causes localized mechanical pain that may be unilateral and radiate to the arm 3
• Osteophyte formation and foraminal narrowing compress nerve roots 1, 4

Critical "Red Flag" Conditions Requiring Urgent Evaluation

You must screen every patient with the following red flags checklist to identify life-threatening conditions: 1, 3

Infection

• Vertebral osteomyelitis or discitis: Look for fever, elevated inflammatory markers (ESR, CRP, WBC), history of IV drug use, immunosuppression 1, 3
• Constitutional symptoms including weight loss, night sweats 1, 3
• Vertebral body tenderness on palpation 3

Malignancy

• Metastatic disease to cervical vertebrae or primary spinal tumors: History of cancer, unexplained weight loss, age >50, intractable pain unrelieved by rest 1, 3
• Constitutional symptoms and elevated inflammatory markers 3

Cervical Myelopathy (Spinal Cord Compression)

• Bilateral symptoms, upper AND lower extremity involvement, long tract signs 2
• Progressive neurological deficits, gait disturbance, hand clumsiness 2, 6
• New bladder or bowel dysfunction, loss of perineal sensation 2
• This requires urgent surgical evaluation as it indicates cord compression rather than simple radiculopathy 2, 6

Inflammatory Arthritis

• Rheumatoid arthritis, ankylosing spondylitis with atlantoaxial instability 3
• Morning stiffness, systemic inflammatory symptoms 1

Vascular Causes

• Vertebral artery dissection: Sudden severe neck pain, posterior circulation stroke symptoms, history of neck trauma or manipulation 1, 3
• This is a neurosurgical emergency requiring immediate vascular imaging 1

Peripheral Nerve and Musculoskeletal Mimics

Peripheral Nerve Entrapment Syndromes

• Distinguish from radiculopathy by distribution pattern: Peripheral nerve entrapments do not follow dermatomal distributions 2, 7
• Carpal tunnel syndrome (median nerve), cubital tunnel syndrome (ulnar nerve), radial tunnel syndrome 7
• Physical examination with nerve-specific provocative tests helps differentiate 7

Brachial Plexopathy

• Consider when symptoms don't fit typical dermatomal pattern or involve multiple nerve roots 2
• May result from trauma, tumor infiltration (Pancoast tumor), radiation, or idiopathic causes 2

Shoulder Pathology

• Rotator cuff disease, adhesive capsulitis, glenohumeral arthritis can refer pain to neck 7
• Differentiate by shoulder-specific examination maneuvers and lack of neurological deficits 7

Diagnostic Algorithm

Initial Assessment Without Red Flags

• Do NOT order imaging initially if no red flags present, as most acute cervical pain resolves spontaneously 3
• Nearly 50% of patients have residual or recurrent pain up to 1 year, but this does not change initial conservative management 1
• Factors associated with poor prognosis: female gender, older age, coexisting psychosocial pathology, radicular symptoms 1

When to Image

If red flags present: Order MRI cervical spine without contrast immediately 3

• MRI is the most sensitive modality for detecting disc herniation, nerve root impingement, infection, tumor, and inflammatory processes 3, 5
• Positive Spurling's test is highly specific for nerve root compression from herniated disc 3

If no red flags but symptoms persist beyond 6-8 weeks of conservative therapy: Consider MRI cervical spine without contrast 3

Imaging Modality Selection

• MRI cervical spine without contrast is the preferred initial imaging for suspected radiculopathy 2, 5
• CT is superior for cortical bone, facet disease, and osteophytes but less sensitive for soft tissue pathology 1
• Plain radiographs have limited value in acute radiculopathy and rarely alter therapy in absence of red flags 1
• CT myelography reserved for patients who cannot undergo MRI 1

Common Pitfalls to Avoid

• Do not assume mechanical cause without screening for red flags - missing infection, malignancy, or myelopathy has devastating consequences 1, 3
• Bilateral symptoms or leg involvement suggests myelopathy, not radiculopathy - this requires urgent evaluation for cord compression 2
• High rate of MRI abnormalities in asymptomatic individuals (up to 50%) means imaging findings must correlate with clinical presentation 1
• Do not order MRI for acute uncomplicated neck pain without red flags - this leads to overdiagnosis and unnecessary interventions 1
• Progressive neurological deficits warrant urgent surgical consultation regardless of symptom duration 2, 6