Chiari malformation is an abnormality of embryonic development causing herniation of the cerebellar tonsils and part of the lower cerebellum into the foramen magnum, and may be associated with hydrocephalus and spinal cord cavitation. It can occur in both males and females, with a slight increase in females of any ethnicity. The onset of symptoms can occur at all ages (1-60 years), with a high incidence at age 35 years and a low incidence after age 65 years. The symptoms of Chiari malformation itself are mainly two symptom groups: first, headache, neck pain, numbness and weakness of upper limbs and/or shoulders, clumsiness and weakness of hands, muscle atrophy, hypesthesia, etc.; second, severe symptoms, which may be accompanied by unstable walking, weakness, nausea and vomiting, hoarseness, loss of gag reflex, tongue atrophy, choking and coughing, weakness of shrugging shoulders, tinnitus, facial pain or numbness, etc.; if accompanied by spinal cord cavity The main reason is that the normal cerebellar tissue herniated into the occipital foramen compresses the spinal cord/brainstem, and this congenital developmental abnormality also causes cerebrospinal fluid circulation abnormalities, resulting in hydrocephalus and spinal fluid (i.e., spinal cord cavity). Chiari malformation can have serious consequences: the patient can die of respiratory arrest during sleep or change of position, so it is important to take it seriously. Diagnosis The main diagnostic method for Chiari malformation is currently MRI of the skull and spinal cord. This malformation can be divided into 5 types, the most common being type 1 (herniation of the inferior tonsillar border into the greater occipital foramen by more than 5 mm). In general, the most common concomitant morbidity is spinal cord cavitation, with approximately 40-75% of chiari type I being associated with spinal cord cavitation, while 90% of spinal cord cavitations have Chiari malformation. A spinal cord cavity is a chronic lesion of the spinal cord that is dominated by several segmentally dilated canaliculi in the center of the spinal cord, which may be separated. The most common site of spinal cord cavitation is the cervical medulla, which may extend superiorly to the intracranial brainstem and caudally to the thoracic or lumbar segments of the spinal cord. Symptoms depend on the extent of involvement: the cervical cord may have pain, sensory and motor abnormalities in the upper extremities and shoulders; the thoracic cord may have pain and sensory abnormalities in the chest and abdomen; the lumbar region and conus may have low back and leg pain, abnormal sensation in the perineum, and abnormal bowel movements. The treatment of Chiari malformation is controversial, but there is a worldwide consensus that surgery is not required for asymptomatic cases and decompression is the best method for symptomatic cases. There is no uniform standard for the scope and criteria of decompression surgery, but the trend is toward minimally invasive. If there is hydrocephalus, especially spinal cord cavity, the symptoms caused by both of them sometimes will not improve after surgery, which is one of the main problems for clinicians. Some patients whose symptoms are relieved after surgery will relapse or worsen after a period of time for reasons that have not been clarified.