Submicrocephalic herniation malformation, also known as Chiari malformation, Arnold-Chiari malformation (Arnold-Chiarimalformation), Arnold-Chiari syndrome, A-Ki malformation, basal pressure tracing syndrome, etc. I. Overview: Chiari malformation (subhypophyseal herniation malformation) refers to a congenital malformation in which the inferior cerebellar earthworm or both the lower part of the brainstem and the fourth ventricle protrude downward in a lingual or wedge shape and cross the foramen magnum to embed into the spinal canal. Type I: Downward displacement (herniation) of the cerebellar tonsils to below the level of the foramen magnum. Type II: Herniation of the cerebellar earthworm, the fourth ventricle, and the inferior brainstem below the level of the foramen magnum, usually accompanied by spinal cord hypoplasia. Type III: Herniation of the cerebellum and brainstem into the upper cervical segment within a spinal bulge. Type IV: cerebellar hypoplasia without subcerebellar herniation. Etiology 1.Developmental disorder theory. 2, the theory of pulling. 3, medical factors. Clinical manifestations 1.More common in females than males, type I in adults, type II in infants, type III in newborns, type IV in infants. Adults with Chiari type I malformation present with spinal cord hollow-like sensory disorder, nystagmus, headache, burning sensation in the neck, shoulder or deep arm, muscle atrophy of upper limbs and hands, spastic paraplegia, bulbar palsy, tongue muscle fiber tremor and tongue muscle atrophy, dysphagia and respiratory distress, scoliosis; adolescents present with spastic weakness of upper or (and) lower limbs, spinal cord hollow-like sensory disorder, hand and (or) upper limb muscle atrophy, and scoliosis. The adolescents show spastic weakness of upper or (and) lower extremities, spinal cavity-like sensory impairment, hand and/or upper extremity muscle atrophy, trunk ataxia, Ⅻ pair of cerebral nerve palsy, and scoliosis. 3, Chair II malformation is common in children with combined spinal bulge, wheezing and hypoxia at birth or within 2 weeks after birth represents brainstem involvement, followed by dysphagia, feeding reflux from the nose and quadriplegia, which should be rapidly decompressed; children and adolescents with insidious onset may have syncope, nystagmus, vibratory hallucinations, posterior group cerebral nerve palsy, and often spinal fluid, limb weakness and tonicity. Infants with Chiari II malformation show inhalation wheezing, intermittent hypoxia, loss of gag reflex, nystagmus, receding neck, weak or absent cry, spastic paralysis of upper limbs, hyperactive deep reflexes, increased muscle tone, peripheral facial nerve palsy or mild paralysis; children show nystagmus, spastic quadriplegia or weak upper limbs, hyperactive muscle tone, hyperactive tendon reflexes, trunk ataxia, recurrent The children showed nystagmus, spastic quadriplegia or upper limb weakness, hypertonia, hyperactive tendon reflex, truncal ataxia, recurrent aspiration pneumonia, and reduced or absent cough reflex. Diagnosis: The diagnosis can be confirmed based on the above typical clinical manifestations, combined with the following imaging examinations. 1.X-ray in intermediate, forward-flexed and backward-supinated positions can show enlarged spinal canal and bony deformities in the atlanto-occipital region, and positive contrast contrast imaging of the spinal cord or pneumoencephalography can show subungual herniation of the cerebellar tonsils. 2.CT can show enlarged fourth ventricle, hydrocephalus and bone abnormalities, etc. Thin layer CT is more likely to find cervical spine, occipital foramen and slope of atlanto-occipital region bone deformity. 3. MRI can clearly show the subungual herniation of cerebellum and its degree, the location of the fourth ventricle, the size of the ventricle, the presence of hydrocephalus, and the presence of spinal cavity or hydrocele. Specific surgical methods include simple posterior cranial fossa decompression, cavernous spinal subarachnoid shunt, posterior cranial fossa small bone window decompression + subchondral cerebellar tonsil electrocautery/partial resection + duralplasty, etc., of which posterior cranial fossa small bone window decompression + subchondral cerebellar tonsil electrocautery/partial resection + duralplasty is the main treatment. For hydrocephalus, long-term relief can also be obtained by ventriculo-abdominal shunt.