What is brain herniation? Brain herniation is caused by a continuous increase in intracranial pressure that displaces part of the brain tissue in the direction of least resistance and squeezes it into some narrow fissures, causing pressure on the brain tissue, nerves and blood vessels there and producing the corresponding symptoms. The location of the foramen magnum, medulla oblongata and cerebellar tonsils is called the foramen magnum where the cranial cavity is connected to the crista medullaris, and the medulla oblongata is connected to the crista medullaris at this foramen, and the cerebellar tonsils are located dorsal to the lower end of the medulla oblongata. What is cerebellar tonsillar herniation? Herniation of the cerebellar tonsils, also known as herniation of the foramen magnum, mostly occurs when a hematoma or an occupying lesion in the posterior cranial fossa directly causes a severe increase in pressure in the subcranial cavity, causing the cerebellar tonsils to be squeezed and herniated downward; the volume of the posterior cranial fossa is small, so its buffer volume is also small. The foramen magnum herniation is formed. Severity and clinical manifestations of cerebellar tonsillar herniation The medulla oblongata is an important afferent and efferent pathway of the central nervous system, where the 5th to 12th pairs of cerebral nuclei are concentrated, and is an important functional hub for the physiological activities of whistling, circulation and internal organs. When local intracranial pressure is increased by an occupying lesion in the posterior cranial fossa, or when an occupying lesion in other parts of the skull causes a continuous increase in intracranial pressure in the upper curtain, cerebral crest fluid flows into the spinal canal through the foramen magnum. The volume of the subarachnoid space, including the cerebellar medullary pool, gradually decreases, and the cerebellar tonsils and adjacent cerebellar tissues on both sides may herniate downward into the spinal canal through the foramen magnum. Although the medulla oblongata is more fixed than the cerebellar tonsils, it also has different degrees of downward axial displacement. If the lesion in the posterior cranial fossa is biased to one side, the downward displacement of the cerebellar tonsils is also biased to that side. In addition to axial displacement, the medulla oblongata may also have a deviated displacement. The subluxed brain tissue is pressed against the hard bone edge of the foramen magnum to form a clear circular indentation. In severe cases, this can cause blood supply disorders and lead to sudden death of the patient. In patients with foramen magnum herniation, if there is axial subluxation of the medulla oblongata, the cervical nerve roots are stretched, causing pain and forced head position in the occipitocervical region. Dysfunction of various cerebral nuclei in the medulla oblongata can cause bradycardia, increased blood pressure, and slow inspiration. Irritation of the base of the fourth ventricle causes symptoms such as recurrent vomiting, dysphagia, and numbness and dissimilarity of the face. The vestibular nucleus is affected, and some patients develop nystagmus and balance disorders. However, the patient’s state of consciousness often remains awake and the pupils are rarely altered. If there is a trigger that suddenly increases ICP or disrupts the pressure balance of cerebral crest fluid, such as coughing, vomiting, struggling, poor whistling, or performing lumbar puncture, neck compression test, or intracerebroventricular injection of drugs or gas, the brain herniation can suddenly increase and lead to whistling arrest, coma, and then circulatory collapse and death. Treatment of cerebellar tonsillar herniation First, because of the obstructive hydrocephalus, ventricular puncture and drainage and dehydrating drugs should be performed promptly to lower the intracranial pressure, and then the primary posterior cranial fossa lesion should be treated. The posterior border of the foramen magnum and the posterior arch of the first cervical vertebra are removed during surgery, and the dura is opened to release the compression of the cerebellar tonsillar herniation. In cases of whistling arrest, assisted whistling and simultaneous ventricular puncture and drainage should be performed immediately, and intravenous dehydrating drugs should be given.