Pain and numbness in the left arm, common causes are as follows: 1, vascular diseases: including limb artery thrombosis, thromboembolism, ischemic changes caused by vascular entrapment, can appear similar damage. In thoracic outlet syndrome, vascular compression can also occur, while manifesting as transient numbness and numbness pain symptoms; 2, neurological diseases: commonly cervical spondylosis, which can be accompanied by posterior occipital, neck and shoulder soreness, stiffness, pain and numbness from the arm down, and also weakness of the limb. Other nerve-related problems, too, need to be differentiated from intracranial disease, but in the case of acute cerebrovascular disease, there is usually numbness in the limbs and relatively few painful symptoms. There are also peripheral nerve injuries, such as elbow canal syndrome, which can also present with painful numbness in the arms. For some other peripheral nerve diseases, such as alcoholic and diabetic, most will show generalized nerve involvement, and unilateral involvement is relatively uncommon. In addition, local nerve tumor compression will also present with corresponding symptoms.