The main causes of numbness on one side of the arm in the elderly are seen in cervical spondylosis, cerebrovascular disease, peripheral nerve disease, etc., as follows: First, cervical spondylosis: cervical spondylosis, due to cervical spine osteophytes, compresses the nerves and causes numbness on one side of the patient’s hand. Second, cerebrovascular disease: many elderly people are often accompanied by small strokes, such as cerebral infarction, lacunar cerebral infarction, which can lead to the destruction of the sensory nerve center on one side of the cerebral hemisphere, so there can be numbness in the other side of the limb, including the arm. Third, peripheral nerve disease: for example, due to trauma and other reasons resulting in damage to the radial nerve and ulnar nerve on one side, the patient can appear the phenomenon of numbness in the arm. Fourth, other factors: there are also some diseases, such as multiple sclerosis, intracranial tumors, etc., patients can also appear the phenomenon of limb numbness.