The causes of sudden leg numbness are very many, commonly in the lumbar spine, cervical spine, brain problems, as follows: 1, lumbar spine problems, such as lumbar disc herniation, lumbar spine slippage, lumbar spinal stenosis may cause spinal nerve compression, appear sudden leg numbness; 2, cervical spine problems, cervical spondylosis caused by spinal nerve compression will also appear sudden leg numbness; 3, brain problems, such as cerebral infarction, cerebral hemorrhage can cause Central nerve pressure, there will be a sudden numbness of the legs. Specific causes need to cooperate with the auxiliary examination to clarify the diagnosis, and then actively carry out symptomatic treatment.