II. Epidemiology

  1. Incidence: 1.64 per 100,000 (rare)
  2. Age: 30 to 70 years old

III. Etiology

  1. Post-Viral (reported in 25% of cases)
  2. Allergic Reaction
  3. Post-Trauma
    1. Postoperative
    2. Pitching
    3. Backpacker palsy
      1. Hikers or military carrying a heavy backpack for hours
      2. Results in compression and traction at the Brachial Plexus

IV. Symptoms

  1. Shoulder weakness follows pain within 1 to 30 days
  2. Hand Paresthesias may be present
  3. Acute severe Shoulder Pain or arm and Neck Pain for 1-2 weeks
    1. Sharp, intense pain
    2. Worse at night
    3. Pain of short duration

V. Signs

  1. Scapular Winging
  2. Weakness occurs in multiple ShoulderMuscle groups
    1. Deltoid Muscle
    2. Rotator cuff Muscles
    3. Biceps Muscle
    4. Triceps Muscle
  3. Non-dermatomal sensory loss typically develops
    1. Especially lateral antebrachial cutaneous (radial aspect of Forearm)

VI. Diagnostics

  1. Electromyogram shows neurogenic atrophy

VII. Differential Diagnosis

  1. Cervical Radiculopathy
    1. Dermatomal Distribution of deficits (non-dermatomal in Acute Brachial Neuritis)
    2. Spurling's Test typically positive (negative in Acute Brachial Neuritis)
  2. Rotator Cuff Syndrome
  3. Extremity Trauma
  4. Acute Shoulder Arthritis
  5. Adhesive Capsulitis

VIII. Management

  1. Symptomatic care
  2. Corticosteroids may be considered (but not consistently supported by literature)

IX. Prognosis

  1. Full recovery in 89% by 2-3 years
  2. Recurrence in up to 25%

X. References

  1. Delaney, Orman, Herbert in Herbert (2016) EM:Rap 16(12): 3-4
  2. Simon (2023) Am Fam Physician 107(5): 503-12 [PubMed]

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