What is cerebellar tonsillar hernia deformity

The cerebellar tonsillar hernia is a congenital developmental anomaly caused by various factors affecting embryonic development. The lower part of the cerebellar tonsil appears to descend below the foramen magnum and even into the cervical canal. In severe patients, part of the lower medulla oblongata and the lower part of the fourth ventricle may also protrude into the cervical canal. Patients with cerebellar tonsillar hernia are often associated with other craniocervical malformations, such as myelomeningocele, syringomyelia, spina bifida, etc., which can cause hydrocephalus due to obstruction of cerebrospinal fluid circulation. The common clinical manifestations are headache, nausea, vomiting, poor limb strength, hypothermia, dysphagia, ataxia, etc.