There are two common causes of arm numbness during sleep: First, due to a fixed sleeping position, so that the arms are in a fixed state for a long time, especially by the body will lead to arm numbness, after posture correction, will soon be corrected and alleviated. Second, the nerve root type cervical spondylosis, this is due to the nerve root itself has been stimulated by the protruding cervical disc or hyperplasia of the cervical spine bone spurs and lead to injury, but due to the correct posture during the day, no long time fixed, may not be heavy symptoms or symptoms disappear, when sleeping pillow posture improper or improper sleeping posture, will lead to arm numbness, nerve stimulation.