Decompression of the posterior fossa for Chiari type I malformation

The occipital macropore area refers to the area formed by the occipital macropores and the first to second cervical vertebrae and their ligaments. Congenital malformations occurred in this department: 1 flat skull base; 2 skull base sag; 3 sacral occlusion fusion; 4 cervical vertebra segmentation insufficiency (Klippel-Feil syndrome); 5 atlantoaxial dislocation; 6 cerebellar tonsil mandibular deformity ( Chiari malformation). These malformations can occur alone or in two or three malformations. When the flat skull base, the atlas fusion, and the cervical spine insufficiency occur alone, most of the symptoms without nerve compression can be treated by non-surgical methods; in the early stage of atlantoaxial dislocation, most of the head traction, manual reduction or head and neck thoracic plaster fixation, or The occipital and cervical fusion can be corrected. If the anterior dislocation of the atlas is difficult to reset, the odontoid process of the vertebral vertebral can be removed by the oral cavity. However, the more treatment is the type I malformation of the cerebellar tonsil. Milhorat et al (1999) reported 364 cases of cerebellar tonsillar sacral type I malformation, 64% with syringomyelia, 12% with skull base. Clinical symptoms are more, although the progress is slow, but once the medullary or cervical spinal cord compression occurs, quadriplegia, muscle atrophy, sensory disturbance and cerebellar symptoms often occur. In severe cases, there may be increased intracranial pressure, or even occipital foramen magnum, leading to consciousness. The obstacle, or the sudden stop of breathing and death. Therefore, for these two types of patients, regular follow-up observation should be performed immediately. Once the symptoms are aggravated, surgery should be performed immediately. The surgical method is decompression of the posterior cranial fossa to relieve the compression of the medulla and upper cervical spinal cord, restore the smooth circulation of the cerebrospinal fluid, and fix the unstable atlantoaxial vertebra if necessary. Treatment of diseases: increased intracranial pressure in the elderly, cerebellar tonsillar malformation Indication Chiari type I malformation of the posterior fossa is applied to: 1. X-ray or MRI examination confirmed the cerebellar tonsil mandibular deformity. 2. There are symptoms of medullary and upper cervical spinal cord compression. 3. The posterior group of cranial nerves are affected by hoarseness, difficulty swallowing, unclear language or atrophy of the tongue muscle, and progressive aggravation. 4. Pillow pain, strong or difficult neck activity, and signs of cerebellar tonsil sputum such as respiratory disorders. 5. There are cerebrospinal fluid circulation disorders, and those with increased intracranial pressure. Contraindications 1. Cerebellar tonsil sputum type I malformation, but no symptoms or symptoms are mild, no significant progress, can not temporarily surgery. 2. Inflammation of the occipital and neck skin. Preoperative preparation 1. Detailed X-ray examination of the cranial neck to determine the type of deformity, it is best to do MRI examination, to understand the plane of the cerebellar tonsil squat; to understand whether there is hydrocephalus or syringomyelia, in order to develop a surgical plan. 2. Understand the stability of the occipital joint and the upper cervical vertebra; remove the atlantoaxial dislocation. 3. Other craniotomy of the same cranial fossa. Surgical procedure Incision The median incision of the occipital region begins at 3 cm from the occipital trochanter, and reaches the plane of the fifth cervical vertebrae. The muscles are cut along the midline, including the suboccipital muscles and the paravertebral muscles of the first to third cervical vertebrae, exposing the occipital bone and the first to third Cervical lamina. 2. Bone window craniotomy According to the method of suboccipital decompression under the cranial fossa, the occipital bone is removed and the posterior margin of the foramen magnum is carefully bitten. For patients with skull base stagnation, the edge of the foramen magnum is sunken to the skull. The posterior arch of the atlas can be close to or fused with the occipital foramen. Therefore, it is more difficult to cut the posterior margin of the occipital foramen. It can be ground with a high speed micro drill. Because of the small volume of the posterior cranial fossa of patients with this disease, the occipital squamous resection should be extensive, with the posterior margin of the mastoid on both sides, from the top to the lower edge of the transverse sinus, and the posterior margin of the foramen magnum. At the same time, the posterior arch of the atlas and the second cervical vertebrae should be removed. 3. Excision of thickened soft tissue After the cranial and upper cervical laminectomy, the fascia near the large hole of the occipital bone should be carefully and patiently removed, and some of them are banded and thickened. In severe cases, the dura mater at the posterior margin of the foramen magnum and the posterior arch of the atlas has obvious impression, indicating that the deformed bone compresses the nerve tissue. 4. Cut the dura mater Due to deformity of the bone, the dura is tight, the occipital large pool disappears or the upper cervical spinal canal is narrowed, and the nerve tissue is still compressed after the bone compression is relieved, so the dura mater must be cut. Starting from the normal cerebellum, the "Y" shape cuts the dura mater. After the incision passes over the occipital foramen, the dura mater is cut along the midline. In the cranial fossa of the baby, there are often malformed veins in the dura mater. The parts are extremely irregular. Sometimes the occipital sinus and sinus are enlarged, and the position of the transverse sinus or sigmoid sinus also varies. Therefore, attention should be paid when cutting the dura mater. In addition, the dura mater often adheres to nerve tissue near the large hole of the occipital bone and should be carefully separated. In patients with a light, simple skull base, the symptoms of compression can be relieved after removal of bone and banded soft tissue. Therefore, some people advocate that it is not necessary to cut the dura mater. This can prevent blood from entering the subarachnoid space and cause adhesions in the future. It is not necessary to perform lumbar puncture after surgery. 5. Separation of intracranial adhesions After the dural incision, it is best to operate under the operating microscope, carefully separate the arachnoid near the large pool of the pillow, and cut off all the band-like fiber strands. The adhesion of the dura mater to the tonsils, medulla, and cervical spinal cord underneath should be separated as much as possible. The subarachnoid space in the large occipital region should be cut open to remove part of the thickened arachnoid membrane. 6. relieve cerebrospinal fluid obstruction For patients with cerebellar tonsillar malformation, the cerebrospinal fluid obstruction should be removed as much as possible. The cerebellar tonsils are tongue-shaped and have large holes in the occipital bone. Some can reach the plane of the third cervical vertebra. If the lower edge of the tonsil is not seen, it should continue to expand downward until the tonsils are completely exposed. After loosening the adhesion around the tonsils under the microscope, the tonsils can be gently separated, the mesopore in the fourth ventricle is explored, and the adhesion near the mesopores is separated. If the obstruction has been lifted, the cerebrospinal fluid flows out of the mesopores. For patients with severe adhesions, Bertrand advocates the removal of the middle and lower part of the cerebellar tonsil: bipolar electrocoagulation of the small blood vessels in the dorsal tonsil, after the pia mater is removed, the tonsils are removed with a suction device and the bleeding is completely stopped, but many people do not advocate this. Large branches of the inferior cerebellar artery near the tonsils should be preserved to ensure blood supply to the cerebellum and medulla. If the large hole of the occipital bone is tightly attached, hindering the dissection of the tonsil and not opening the middle hole, the lower part of the cerebellum is opened, and the fourth ventricle is opened to release the obstruction. If there is difficulty in cutting the ankle, the obstructive hydrocephalus is not relieved, and the shunt can be performed according to the hydrocephalus treatment method. 7. Dura mater treatment Most authors believe that the dura mater is not sutured after surgery, but Bertrand emphasizes that the dura mater should be sutured to prevent blood from entering the cerebrospinal fluid. He believes that postoperative muscle oozing, after entering the subarachnoid space, stimulate the meninges, traffic hydrocephalus can occur, so the dura mater should be sutured. In order to prevent compression after dural suture, it can be repaired by dry frozen dura mater, which is the most ideal meningeal repair material. After the dural repair and suture, the extradural vacuum drainage should be performed. 8. Close the incision The muscles and skin are tightly sutured in layers. complication Respiratory failure The main reason is excessive head and neck flexion and extension and intraoperative medulla damage. 2. Cerebrospinal leak Mainly the muscle suture is not tight enough, especially at the upper end of the muscle. In order to prevent this complication, 0.5 cm should be left in the muscle cutting of the occipital trochanter below the occipital trochanter for suturing. It is forbidden to peel all the attachment parts of the muscle from the occipital bone. For the weak area to be reinforced and sutured, if it is not possible to strengthen, a pedicled myofascial flap can be made in the vicinity, and the suture is overlapped. If cerebrospinal fluid leakage occurs, the suture should be debrided early, the drainage should be placed under the skin, and another incision should be made from the healthy skin, and then the original incision is healed and then removed. If a wound infection occurs and can not be sutured, lateral ventricle drainage can be performed to strengthen anti-infective treatment and promote wound healing.