If the left side of the back is numb, consider the following diseases: 1, back fasciitis, accompanied by back pain, pain aggravated by activity, light activity, heat application, local pressure with pain, consider the neck and back fasciitis caused by prolonged bending, low head. 2, if only simple numbness, consider intercostal neuralgia caused by local sensory abnormalities, is a manifestation of intercostal nerve damage, clinically is more common. 3, cervical spondylosis, if accompanied by neck pain and arm radiating pain, numbness, with prolonged head bowing habits, consider cervical spondylosis is more likely. 4, elderly patients who used to have cerebral pain and arm radiating pain, numbness, consider cervical spondylosis. If the patient has a history of cerebrovascular disease in the past, such as cerebral infarction or cerebral hemorrhage, it cannot be ruled out that it is caused by cerebrovascular disease.