Numbness and pain in the arm may be a sign of cervical spondylosis, brachial plexus nerve injury and cerebrovascular disease. 1. Cervical spondylosis: It is mainly seen in cervical radiculopathy, because cervical intervertebral disc herniation can cause numbness and pain in the arm and stiffness in the neck and shoulder by compressing the neighboring nerve roots. 2. Brachial plexus nerve injury: if the head or shoulder is moved in the opposite direction and separated due to violence, it can lead to injury of the upper trunk of the brachial plexus and involve the middle trunk, which can cause numbness, pain and weakness of the arm. 3. Cerebrovascular disease: ischemia of small blood vessels in the cranium, causing degeneration and necrosis of brain cells, which will cause numbness, pain and weakness in the limbs of the corresponding innervated areas of the brain nerves. Numbness and pain in the arm may also have other reasons, it is recommended to improve the relevant examination in time to clarify the cause, so as not to delay the condition.