Unilateral arm numbness, may be related to mechanical compression, may also be due to cervical spondylosis, cerebrovascular disease, ulnar tube syndrome and other reasons. 1. Mechanical compression: commonly found in sleeping on the side for a long time, resulting in unilateral arm pressure for a long time, resulting in poor blood circulation of the arm on the side of the pressure, which may cause unilateral arm numbness. 2. Cervical spondylosis: commonly seen in vertebral artery-type cervical spondylosis, which can easily lead to brachial plexus nerve root compression, which may cause unilateral arm numbness, and may also be accompanied by upper limb weakness, neck and shoulder pain, dizziness and other symptoms. 3. Cerebrovascular disease: commonly seen in acute cerebral hemorrhage or acute cerebral infarction, due to ischemia or hemorrhage in the local brain tissue, resulting in damage to the cerebral nerves in the area, causing cerebral dysfunction, which may show unilateral numbness of the arm, and may be accompanied by numbness of the lower limbs, speech disadvantage and other symptoms. 4. Elbow tube syndrome: it is caused by trauma or inflammation caused by the injury resulting in congestion, edema, adhesion, or tendon sheath cysts and other occupying lesions resulting in ulnar nerve compression and caused by the symptoms of unilateral arm numbness. Unilateral arm numbness, may also be caused by other reasons, if the symptoms continue to be unable to relieve, or there are other obvious discomfort, you should seek medical attention as soon as possible, after clarifying the causes, to give targeted treatment.