What Is Involved in Chiari Malformation Surgery?

1. Hydrodynamics says hydrocephalus in the fetus is due to secondary deformities due to pressure differences in the cranial and spinal canals.

Amold-Chiari deformity

Arnold-Chiari deformity (basal impression syndrome), also known as Arnold-Chiari syndrome. This disease refers to the deformity of the lower cerebellum or both the lower part of the brainstem and the fourth ventricle, which protrudes downwards and is inserted into the spinal canal across the foramen magnum. The etiology of this disease is unknown, and there are three opinions.

Pathogenesis of Amold-Chiari deformity

1. Hydrodynamics says hydrocephalus in the fetus is due to secondary deformities due to pressure differences in the cranial and spinal canals.

2. The doctrine of spinal cord is fixed at the site of spinal meningocele and is pulled down as it develops.

3 The deformity theory has too much hindbrain development and hypoplasia.

Clinical manifestations of Amold-Chiari deformity

Headache and optic disc edema such as increased cranial pressure, ataxia (represented by cerebellar or spinal ataxia), pyramidal tract sign, posterior cranial nerve and upper cervical spinal nerve paralysis.

Brainstem and cerebellar MRI examinations can reveal changes in the cerebellar subtonsillar hernia.

Diagnosis of Amold-Chiari deformity

Chronic intracranial hypertension, ataxia, pyramidal tract sign, high cervical spinal cord and bulbar syndrome, combined with MRI findings, the disease is not difficult to diagnose.

Differential diagnosis of Amold-Chiari deformity

(1) Identification of congenital malformations at the junction with other cranial vertebrae

1. Skull base invagination is a deformity of the skull base bone with the occipital foramen as the center. The main changes are flattening of the occipital bone, distortion of the occipital foramen and reduction of the anterior and posterior diameter, often accompanied by atlanto-occipital fusion.

2. Occipitalization Occipitalization: Partial or complete fusion of the atlanto-occipital, occipital bone offset, accompanied by rotation, makes the atlanto-occipital fusion on both sides of different heights. The rise of the dentate process of the vertebra can cause compression of the medullary or cervical spinal cord.

3 Atlantoaxial dislocation A common cause of congenital atlantoaxial dislocation is dysplasia or absence of dentate processes. Atlantoaxial dislocation often results in compression of the medulla oblongata and superior cervical spinal cord.

The above-mentioned congenital malformations can cause symptoms of compression of the medullary and upper cervical spinal cords, and generally have no symptoms of increased cerebellar and cranial pressure. Clinically, it is sometimes difficult to distinguish Amld-Chiari malformations, and it is not difficult to diagnose with the help of x-rays and other imaging tests.

(B) tumors in the posterior cranial fossa and foramen magnum

There may be symptoms of increased intracranial pressure, cranial nerve palsy and cerebellum, which is difficult to distinguish from this syndrome based on clinical manifestations only. CT examination showed substantial occupying of posterior cranial fossa, shift of midline, and signs of hydrocephalus on the curtain. No abnormality was found on cervical X-ray.

Surgical procedure

In the early stage, simple posterior cranial fossa decompression and hollow spinal subarachnoid shunt surgery were mainly used.In the later treatment group, posterior cranial fossa small bone window decompression + subchondral cerebellar tonsillectomy + duraplasty alone posterior cranial fossa Decompression (PFD) The posterior fossa is craniotomy, the occipital scale bone window is about 5 cm × 5 cm, and the width of the occipital foramen is 1.5 to 210 cm. Then according to the degree of the cerebellar tonsil hernia, the extent of the cervical laminectomy is determined so that the cerebellar tonsil can be exposed accurately. Open the dura mater, support the cerebellar tonsil inferior pole, open the median foramen of the fourth ventricle, open the dura mater, suture the neck muscles intermittently, and close the skull.

Decompression of the posterior cranial fossa window + subchondral cerebellar tonsillectomy + duraplasty The posterior cranial fossa bone decompression is smaller than the PFD method, about 3 cm × 3 cm. After opening the dura mater, focus on cobwebs Membrane adhesion bands, sufficient decompression, and partially removed the cerebellar tonsils of the hernia under the pia mater, retracted upwards, explored and dredged the lateral crypts and median foramen to avoid vascular and nerve damage. Finally, a piece of cervical fascia tissue of about 3 cm × 3 cm was taken before closing the skull, and it was closely sutured with the posterior cranial fossa dura mater.

Efficacy criteria were assessed using the Tator result assessment criteria, which were divided into significant improvement, stability, and worsening based on the extent to which patients felt their symptoms and signs improved.

Surgery is the main method to treat this deformity. There are many surgical methods, and there are a lot of arguments about their surgical methods and effects. The prognosis of the open dura mater group is better than that of the unopened dura mater group, which has significant statistical significance (P <0.05) .The postoperative complication rate in the dural repair group is lower than that of the undural group, which has significant statistical significance P <0.05). Therefore, among the many surgical treatments for Arnold-Chiari malformation, posterior cranial fossa decompression + dural sac enlargement and reconstruction is an ideal method.