Differential Diagnosis for Left Shoulder, Neck, and Arm Pain

When a patient complains of left shoulder, neck, and arm pain, it's crucial to consider a broad range of potential causes, given the overlap in symptom presentation among various conditions. The differential diagnosis can be organized into the following categories:

• Single Most Likely Diagnosis:
  • Musculoskeletal (MSK) pain: This is often the most common cause of left shoulder, neck, and arm pain, given the prevalence of musculoskeletal issues such as strain, overuse, or degenerative conditions like arthritis. The pain is typically exacerbated by movement or specific positions.
• Other Likely Diagnoses:
  • Acid reflux: Gastroesophageal reflux disease (GERD) can cause chest pain that may radiate to the arm, neck, or shoulder, often worsened by lying down or eating certain foods.
  • Cervical radiculopathy: Compression or irritation of the cervical nerve roots can cause pain that radiates down the arm, potentially involving the shoulder and neck.
  • Thoracic outlet syndrome: Compression of the nerves or blood vessels that pass into the thoracic outlet (the space between your collarbone and first rib) can cause pain in the shoulders and arms.
• Do Not Miss Diagnoses:
  • Myocardial infarction (MI) / Heart Attack: Although less common, cardiac causes of chest pain, including MI, are critical to identify promptly due to their high morbidity and mortality. The pain is often described as a pressure or heaviness and may radiate to the arm, neck, or jaw.
  • Angina: Similar to MI, angina pectoris is a condition characterized by chest pain or discomfort due to transient myocardial ischemia. It's essential to distinguish from other causes of chest pain due to its implications for cardiac health.
  • Aortic dissection: A tear in the inner layer of the aorta can cause severe, tearing chest pain that may radiate to the back or arms, representing a medical emergency.
• Rare Diagnoses:
  • Pancoast tumor: A type of lung cancer located at the top of the lung that can cause shoulder and arm pain due to local invasion of nerves.
  • Esophageal spasm or rupture: Although less common, these conditions can cause severe chest pain that may radiate to the arm or shoulder.
  • Osteonecrosis or bone tumors: Rare conditions that could cause localized pain in the shoulder or arm, potentially radiating to the neck.

Each diagnosis has a distinct set of characteristics and risk factors. A thorough history, physical examination, and appropriate diagnostic tests (such as ECG, troponin levels, imaging studies) are essential for accurately diagnosing the cause of left shoulder, neck, and arm pain and initiating appropriate treatment.