Numbness of the thumb may be caused by cerebral infarction, radicular cervical spondylosis, carpal tunnel syndrome, diabetic peripheral neuropathy and other reasons, as follows: 1. Cerebral infarction: patients with cerebral ischemia and cerebral infarction may have symptoms of limb sensory and motor dysfunction due to brain parenchyma and brain nerve damage. It may lead to numbness of the thumb. 2. Neurogenic cervical spondylosis: patients with neurogenic cervical spondylosis may experience numbness of the thumb because of the compression of the cervical nerve roots by the protruding intervertebral discs. 3. Carpal Tunnel Syndrome: Carpal Tunnel Syndrome can cause compression of the median nerve, and patients can experience numbness in their thumbs, index fingers, and middle fingers. 4. Diabetic peripheral neuropathy: diabetic patients can be due to peripheral neuropathy and thumb, the back of the hand symmetrical, sock-like sensory impairment. There are many other reasons that can cause numbness of the thumb, and it is recommended that patients consult a regular hospital in time to identify the specific causes of the symptoms and receive treatment as soon as possible.