Numbness of the thumb may be caused by upper extremity nerve entrapment, peripheral neuritis, cervical spondylosis and other reasons. 1. Upper limb nerve compression: the upper arm is compressed when sleeping, the median nerve is compressed in carpal tunnel syndrome, the radial nerve is damaged and other reasons can lead to upper limb nerve sensory impairment and numbness of the thumb. 2. Peripheral neuritis: thumb exposure to toxic substances, vitamin B deficiency, thumb local blood circulation disorders can lead to peripheral neuritis, causing demyelination of peripheral nerves, thumb numbness. 3. Cervical spondylosis: cervical spondylosis such as cervical disc herniation, vertebral small joint osteophytes and other cervical spondylosis oppresses the neighboring cervical nerve roots, and the patient will experience numbness of the thumb, accompanied by radiating pain in the upper limbs and other symptoms. If the numbness of the thumb can not be relieved in time, you should consult a doctor for examination, under the guidance of the doctor to clarify the diagnosis, targeted treatment.