Numerous conditions can cause pain, numbness and tingling in the left arm. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, or NIAMS, pain, numbness and tingling in the left shoulder and arm may indicate a myocardial infarction, or heart attack. However, other conditions may be more likely to cause left-sided arm pain, numbness and tingling. In most cases, conditions causing these symptoms are not a medical emergency and respond well to conservative care methods.
Thoracic Outlet Syndrome
Thoracic outlet syndrome is a musculoskeletal condition that can cause pain, numbness and tingling in the left arm. According to the National Institute of Neurological Disorders and Stroke, or NINDS, thoracic outlet syndrome is caused by the compression of nerves or blood vessels as they course through the narrow passageway leading from the lower neck to the axilla or armpit. Possible signs and symptoms associated with thoracic outlet syndrome include pain in the neck, shoulder and arm on the affected side, arm numbness and tingling, aching pain in the arm and hand, decreased grip strength, skin discoloration in the hand and arm swelling. The Mayo Clinic states that possible causes of thoracic outlet syndrome include anatomical defects such as a cervical rib, poor posture, traumatic injuries, repetitive activity, obesity, increased joint pressure and pregnancy.
Cervical Disc Herniation
A cervical disc herniation can compress nerve roots in the neck and cause pain, numbness and tingling in the left arm. The Mayfield Clinic--one of the world's largest neurosurgical practices--states that a cervical disc herniation is a spine condition in which the center of a spinal disc--the nucleus pulposus--ruptures through a weak spot in the disc's fibrous outer ring. In some cases, the herniated disc material protrudes into the spinal column or the hole through which the spinal nerve roots-- offshoots of the spinal cord--exit the spinal column, compressing or irritating the nerve roots and causing arm pain, numbness and tingling on one side of the body. Cervical disc herniation symptoms largely depend on the specific disc that ruptures, although common signs and symptoms include pain that radiates down the neck and arm and into the hand, arm numbness and tingling, muscles spasms, arm muscle weakness and decreased grip strength.
Brachial Plexus Injuries
Brachial plexus injuries involve nerve damage that can cause pain, numbness and tingling in the left arm. According to the American Society for Surgery of the Hand, or ASSH, brachial plexus injuries, also known as Erb's palsy, are characterized by damage to the network of nerves that travel from the neck to the arm via the axilla or armpit. The most common cause of brachial plexus injuries is an overstretching of the neck. In most cases, the head and neck are violently forced away from the affected shoulder while the shoulder is depressed or forced downward. Motorcycle accidents and contact sports injuries are common sources of brachial plexus injuries. Possible signs and symptoms associated with brachial plexus injuries include an electrical shock-like sensation down the arm, numbness and tingling in the arm and, in more severe cases, the inability to use the arm or fingers.