What is the cause of shoulder pain radiating down the arm, accompanied by numbness and tingling in the lower arm and fingers, particularly when moving the arm in a certain way?

Differential Diagnosis for Shoulder Pain Radiating Down the Arm

Single Most Likely Diagnosis

• Cervical Radiculopathy: This condition, often resulting from a herniated disc or bone spur in the cervical spine, compresses or irritates a nerve root, leading to pain, numbness, and tingling in the arm and fingers. The symptoms described, especially the radiation of pain and the specific mention of numbness and tingling in the lower arm and fingers when moving the arm, are classic for cervical radiculopathy.

Other Likely Diagnoses

• Thoracic Outlet Syndrome (TOS): This condition involves compression, injury, or irritation of the nerves and/or blood vessels (arteries and veins) in the thoracic outlet area, which lies between your collarbone (clavicle) and first rib. It can cause pain in your shoulders and neck and numbness in your fingers.
• Subacromial Bursitis or Rotator Cuff Tendinitis: While these conditions primarily cause shoulder pain, they can sometimes radiate pain down the arm, especially if there is significant inflammation or if the rotator cuff tendons are severely affected.
• Brachial Plexus Injury: An injury to the brachial plexus, the network of nerves that conducts signals from the spinal cord to the shoulder, arm, and hand, can cause pain, numbness, and tingling in the arm and fingers.

Do Not Miss Diagnoses

• Cervical Spinal Cord Compression: Conditions such as cervical spondylotic myelopathy or a spinal tumor can compress the spinal cord, leading to serious neurological deficits if not promptly addressed. Symptoms can include pain, numbness, tingling, and weakness in the arms and legs.
• Acute Coronary Syndrome: Although less common, chest pain or discomfort that radiates to the arm can be a sign of a heart attack, especially if accompanied by other symptoms like shortness of breath, nausea, or sweating.
• Pancoast Tumor: A type of lung cancer located at the top of the lung, which can invade the brachial plexus and cause shoulder and arm pain, as well as numbness and tingling in the fingers.

Rare Diagnoses

• Multiple Sclerosis: An autoimmune disease that affects the brain and spinal cord, leading to a wide range of neurological symptoms, including numbness, tingling, and pain in various parts of the body, including the arms.
• Peripheral Neuropathy: Damage to the peripheral nerves can cause numbness, tingling, and pain, typically in a glove-and-stocking distribution but can sometimes affect the arm and fingers in a more localized manner.
• Complex Regional Pain Syndrome (CRPS): A chronic pain condition characterized by severe, burning pain at the site of an injury, which can sometimes occur in the arm and hand, accompanied by swelling, skin changes, and hypersensitivity.