First of all, spinal cord cavity is a disease caused by a variety of reasons, some are related to submicrocephalic tonsillar herniation deformity, and some are related to tension pulling at the lower end of the spinal cord (end filament tension and tethering), and the problem of the end filament is often overlooked. In order to make a comprehensive and systematic evaluation without missing important etiologies, MRI of the lumbar spine should be checked. Secondly, fine cavities, those with less severe submicrocephalic tonsillar herniation, those with spinal cord atrophy, cavity atrophy, and If the spinal cord cavity exceeds the upper thoracic segment, if there is scoliosis, if there is low back pain and distension, if there is soreness and weakness in legs and feet, if there is frequent urination, urgent urination, urinary leakage and dry stool, it is more likely that there is tension in the lower end of the spinal cord (end filament tension), so MRI of the lumbar spine is very important and must be checked, and it is necessary to check the whole area thin layer scan of the lumbosacral region. Third, to clarify the presence of sacral cysts and spina bifida and other related conditions, lumbar spine MRI examination is necessary.