Numbness in the left leg of men is considered to be a sign of lumbar spine disease, lower limb vascular disease, neurological disease and other diseases. 1. Lumbar spine diseases: such as lumbar disc herniation, lumbar spinal stenosis, etc., when these lesions for the nerve root caused by the compression, will cause the lower limbs of radioactive pain, numbness and weakness and other symptoms. 2. Lower extremity vascular diseases: for example, arteriosclerosis of the legs, varicose veins, etc. These diseases will cause insufficient blood supply to the legs, which will also cause numbness in the left leg. 3. Neurological diseases: for example, cerebral infarction, craniocerebral tumor, etc. These diseases can cause nerve function damage, which can also cause numbness of the left leg, and can be accompanied by slurred speech, limb weakness and other symptoms. The causes of numbness of the left leg are very many, such as the sudden onset of the disease or accompanied by symptoms such as limb weakness, you should consult a doctor in time for treatment.