I. Pathogenesis In 1873 Oliven first proposed the disease, in 1891 ArnoldChiari through autopsy found that congenital malformation of the foramen magnum area, most of them have spinal cord cavity, therefore, often called ArnoldChiari malformation. With the development of embryology and the widespread use of MRI in recent years, the following theories of pathogenesis have been developed: 1, liquid power theory (water hammer effect): This is the theory of cerebrospinal fluid pressure wave transmission proposed by Dyste in 1989. It is believed that the cerebrospinal fluid circulation is obstructed due to occipital foramen magnum malformation and subhypothalamic herniation compression, and when the cerebrospinal fluid pulses, it cannot pass smoothly in the subarachnoid space, and the cerebrospinal fluid injected within the four ventricles has a water hammer-like effect, which impacts the latch of the lower part of the four ventricles that has been occluded in the embryo during each pulsation, causing the CSF to be injected into the central canal of the spinal cord, causing the CSF to accumulate in the central canal and form a cavity. 2, cranial-spinal subarachnoid cerebrospinal fluid pressure separation theory (splash effect): William believes that when the occipital foramen magnum malformation causes the separation of cerebrospinal fluid between the occipital pool and the subarachnoid space in the spinal canal, the cerebrospinal fluid in the heart contraction and diastole pulsation, its flow is blocked in the prograde, retrograde and longitudinal direction, especially when sitting up, holding the breath or puffing, etc. to increase the pressure of the superior vena cava, intracranial subarachnoid cerebrospinal fluid accumulation The spinal fluid accumulates in the subarachnoid space when it is aspirated and enters the central canal, becoming spinal fluid. Due to the dilatation of the central canal of the spinal cord can cause an increase in venous pressure around the spinal vessels and in the interstitial space of the spinal cord tissue, with the beating of the heart, eccentric flow and accumulation of fluid can occur, forming an eccentric spinal cavity-like fluid, also known as the splash effect. 3, other: some people believe that the formation of eccentric cavity is not entirely due to the splash effect, there may be some uncertain causes: such as spinal cord adhesions and other anatomical factors and poor closure of the central canal of the spinal cord. Second, the surgical treatment of spinal cord cavitation General conservative treatment is not able to slow down the further development of the disease. Due to the loss of cerebrospinal fluid cushioning at the cervico-occipital junction, inadvertent injury to the neck may result in serious consequences, such as limb paralysis, respiratory arrest or even death. Surgery is therefore an important tool for the treatment of spinal cord cavitation. In the United States, a survey of neurosurgeons’ opinions on surgical treatment was conducted in 1991 and 1993, and the vast majority of physicians considered life-threatening respiratory impairment as an absolute indication for surgery. More than 80% of physicians believe that posterior cranial fossa decompression is beneficial for spinal cord cavity and recovery of cranial nerve and brainstem function. There is a consensus that surgical treatment should be performed for spinal cord subarachnoid space obstruction complicated by spinal cord cavity with clinical symptoms, such as occipital foramen magnum malformation and submicrocephalic tonsillar herniation malformation, cervical vertebral subsegmental malformation, spinal cord spinal membrane bulge, neural tube closure insufficiency, and intramedullary tumor. The cavity shunt is a further solution to the patient’s disorder. 1, posterior cranial fossa and cervical decompression: Sahuquillo et al. and Bindal et al. proposed the theory of posterior cranial fossa reconstruction, which has certain clinical reference significance. (1) Expand the suboccipital craniotomy, open the foramen magnum and remove the cervical 1-3 vertebral plates as far as possible, reaching down to the lower tonsils; (2) Cut the dura, but keep the arachnoid membrane intact; (3) Fourth ventricular outlet correction; (4) Repair with artificial dural sutures to reconstruct the occipital pool; (5) Place 3-4 silk sutures on the dura through the muscle and fix it to the fascia to prevent dural adhesions. The current surgical concept of “minimally invasive, limited, and adequate decompression” and individualized treatment can maximize the relief of patients’ disorders. Minimally invasive small incisions (about 4-6 cm long), minimally invasive instruments and small bony windows (2X3 cm in size) have been used to treat subungual hernias with spinal cord cavities, and good results have been achieved. Minimally invasive surgery is completely different from conventional major surgery in that it is performed with the assistance of a microscope to perform various operations within the dura mater, such as separating the adhesions between the cerebellar tonsils and the brainstem and relieving the obstruction of the middle foramen of the fourth ventricle, with minimal possibility of damaging the surrounding important structures during surgery. After Oldfield et al. used the surgery of decompression of occipital foramen, resection of posterior arch of cervical vertebra 1-3, dural repair, and keeping the arachnoid membrane intact to treat the subungual herniation malformation of cerebellar tonsils, the subungual herniation was found to disappear and the spinal cord cavity was relieved on MRI 1-4 months after surgery, and the CSF flow rate in the region of occipital foramen increased to 2-3 times of that before surgery. 2.Cavity drainage: It is a further solution to solve the patient’s disease. Nicholas et al. removed half of the lamina or the whole lamina at the widest plane of the cavity, made a small incision at the thinnest point where the posterior spinal nerve root enters the spinal cord using an operating microscope, placed a T-shaped silicone tube, a perforated silicone tube or a Teflon sheet downward into the cavity, drained it into the subarachnoid space, and fixed it with a thin This shunt can maintain a certain potential energy gradient of cerebrospinal fluid, which can better complete the cavity shunt and avoid the adhesion obstruction caused by the cavity-subarachnoid shunt, thus significantly improving the success rate of the operation. In other cases, Logue et al. cut the sensory roots of the spinal nerve on the side near the cavity and placed the distal free in the cavity to drain the subarachnoid space. In some typical cases, good results have been achieved after decompression of the foramen magnum or drainage of the spinal cavity. Of course, for some patients with small and insignificant spinal cord cavities, medical treatment can be performed without surgery.