Left leg numbness is mainly seen as a precursor to the following diseases: 1, if the left leg numbness is persistent, related to the activity or position, consider that the patient may have lumbar disc herniation, this time need to do lumbar spine magnetic resonance examination. 2, if the left leg numbness is localized, such as numbness or discomfort in the left lateral thigh, consider whether the patient has lateral femoral dermatomal neuritis, give vitamin B1, B12, etc. after the nerve nutrition treatment can be relieved. If the numbness of the left leg is persistent with the loss of strength of the left leg, or with numbness, weakness and speech dysfunction of the left upper limb, consider whether the patient has acute cerebrovascular disease, and perform a cranial MRI to clarify.