The numbness of the left thumb is not necessarily a sign of disease, it may be caused by physiological, but also cervical spondylosis, peripheral neuropathy and cerebrovascular disease signs. 1. Physiological factors: numbness of the left thumb is not necessarily a sign of disease, it may be in daily life, sleeping posture is not correct, long time compression of the left thumb, resulting in the blood does not flow, this is a normal physiological phenomenon, adjusting the work and rest will be able to recover. 2. Cervical spondylosis: numbness of the left thumb is a sign of cervical spondylosis. If the patient suffers from cervical disc herniation, cervical myelopathy and other cervical spine disease, the nerve roots of the upper limbs of the human body suffered compression and thus damage, there will be numbness of the left thumb. 3. Peripheral neuropathy: numbness of the left thumb may also be a sign of peripheral neuropathy. Due to the presence of peripheral neuritis, diabetic peripheral nerves and other diseases originating in the peripheral nervous system structure and function of the damage to the disease, there will be numbness of the left thumb symptoms. 4. Cerebrovascular disease: numbness of the left thumb may also be a sign of cerebrovascular disease. Due to cerebral hemorrhage, cerebral infarction, cerebral arteriosclerosis, cerebral vascular malformation and other lesions affecting the sensory conduction pathway, thus causing numbness. Therefore, if the symptoms of numbness of the left thumb, after excluding physiological causes, should consult a doctor in time, under the guidance of the doctor to treat the cause.