Causes of pain and numbness in the left hand are potentially serious, such as in a heart attack, but more likely, are related to imbalances and/or problems in the musculoskeletal system of the upper back and neck or the shoulder and arm that creates the sensations. Modern conservative treatment is effective and ergonomic changes as well as strengthening and stretching exercises can help to prevent recurrences.
Pain and numbness in the left hand, and usually felt in the entire arm and shoulder as well, could be the result of a myocardial infarction (heart attack). Shortness of breath, pain into the throat, deep pain or pressure sensation underneath the breastbone, accompanied by pain in the hand and arm should be determined by a physician if the heart is the cause. However, the pain doesn't necessarily have to be severe; it can be more on the mild side and therefore not provoke one to seek medical help. Upon exam, these patients are usually restless and pale; their skin is cool to the touch and there may be a blue tinge around their lips due to lack of oxygen, according to The Merck Manual.
The nerves that originate in the neck and descend to the arm may be a culprit in causing pain and numbness. If the point at which they exit the spine in the neck has become compromised somehow, the nerve becomes impinged and can lead to symptoms in the hand and arm. During an exam, the health care provider determines which fingers are affected in the hand, because this correlates directly to which nerve has become problematic. It is helpful if the patient can recall if it is the back and/or front of the hand and whether the tips of the fingers are involved because this gives further clues. The most common cause is degenerative joint disease in the cervical spine (neck). According to Yochum and Rowe, it is the fifth and sixth vertebral levels that are the most common to undergo degenerative change and can cause pain and numbness of the thumb and index and middle fingers of the hand as well as on the outside of the shoulder, arm and forearm.
Numbness and pain in the hand can be due to problems in the arm and hand. The median nerve lies underneath the pronator muscle in the forearm. If this muscle is too tight, it can put pressure on the nerve and create sensations in the hand. Similarly, if the carpal tunnel at the wrist has inflamed tendons or swelling within it, one can get the same symptoms. Deep tissue therapy and some physical therapy modalities, even splinting of the wrist can remedy this and help to prevent surgery.