Surgical treatment of intramedullary spinal cord tumors Intramedullary spinal cord tumors account for about 20% of intradural tumors and are one of the common tumors in the central nervous system. Among them, ventricular meningioma and astrocytoma account for about 40% each, hemangioblastoma accounts for about 10%, and nerve sheath tumor, lipoma, cavernous hemangioma, epidermoid cyst, cortical cyst and other tumors also account for about 10%. As early as 1911, successful resection of intramedullary spinal cord tumors was reported, but until the 1950s, only palliative laminectomy and decompression were advocated for intramedullary spinal cord tumors. after the 1960s, the application of microsurgery and ultrasound suction, and after the 1970s, the application of laser and laser microsurgery made great progress in the surgical treatment of intramedullary spinal cord tumors. In the past 20 years, the application of MRI and the rapid development of microsurgery have led to more accurate localization and qualitative diagnosis of spinal cord intramedullary tumors and significantly improved surgical efficacy. At present, most authors believe that it is appropriate to take an active surgical treatment attitude towards spinal cord intramedullary tumors. The authors have calculated the results of surgical treatment of 100 cases of cervical intramedullary tumors, and the total tumor resection rate reached 84.0%, and the postoperative improvement rate reached 76.0%, which also suggests that active surgical treatment for intramedullary tumors of the spinal cord, even for cervical intramedullary tumors, is advisable. Surgery should be performed when the patient has moderate neurological deficits. For low malignant glioma, benign intramedullary tumors such as hemangioblastoma and nerve sheath tumor, total tumor resection should be strived for; for lipoma, subtotal or majority resection is recommended; for high malignant glioma, the aim of surgery is to reduce spinal cord pressure and improve spinal cord function, so tumor resection should be strictly limited to “intracapsular”. The most important surgical technique for spinal cord intramedullary tumor is to separate and remove the tumor strictly along the correct interface after disconnecting the main blood supply of the tumor. The specific surgical method varies with different pathological types: ① Glioma is mostly located in the central posterior part of the spinal cord, when cutting the tumor, the soft spinal membrane is cut along the posterior middle of the spinal cord to reveal the tumor, and after separating slightly to both sides, the soft spinal membrane is suspended with non-invasive sutures; the posterior cords are drawn on both sides and the tumor is resected intracapsularly, at the junction of the tumor and the cavity, one pole of the tumor is freed first, and then the ventral tumor is separated from top to bottom or bottom to top until the whole tumor is removed. If the tumor is free of secondary cavity formation, the tumor will be removed. If the tumor has no secondary cavity formation, or if the tumor is thin and deep at both ends and the cavity wall is thicker, it is difficult to distinguish the tumor-marrow interface, the tumor should be separated and resected in the middle of the tumor until the ideal ventral interface of the tumor is found, and then the ventral tumor should be separated from the upper and lower ends until the whole tumor is resected. The tumor is often located in the dorsolateral part of the spinal cord. When cutting the tumor, the dorsolateral blood supply artery should be cut off by electrocoagulation first, and the soft spinal membrane should be cut at the upper or lower pole of the tumor (the pole away from the main drainage vein) to enter the cavity, electrocoagulate and crumple the tumor envelope, gradually expose and cut off the blood supply artery of the tumor more ventrally by electrocoagulation, and then separate the ventral side of the tumor from the top to the bottom or from the bottom to the top. Then, the tumor is also separated from the ventral side from top to bottom or bottom to top, and so on alternately, electrocoagulation, crumpling of the tumor envelope and dissection of the remaining medial ventral blood supply artery are performed until the tumor is completely free from the spinal cord, and finally the main drainage vein is disconnected to remove the tumor as much as possible in one piece. If the tumor is huge, it is difficult to remove the whole tumor, the blood supply artery can be cut off first, the completely free tumor can be partially removed, and then the remaining tumor can be separated and removed after the tumor section is hemostatic, until the whole tumor is removed. It is not recommended to electrocoagulate the draining vein and enter the tumor for resection before disconnecting the main blood supply artery to avoid uncontrollable bleeding or acute enlargement of the tumor, which may affect the resection of the tumor and accidentally injure the spinal cord tissue. When the dorsal edge of the tumor is obstructed by the draining vein and the posterior root of spinal nerve respectively, it is better to cut off part of the nerve root in order to reveal, separate and resect the tumor, rather than to electrocoagulate the draining vein by chance before clearly separating all the blood supplying arteries, so as not to cause adverse consequences. Therefore, laser surgery is the most suitable treatment for intramedullary lipoma: first, a low-power CO2 laser beam (power density of about 1100W/cm2 is appropriate) is used to cut the tumor up to the subarachnoid space and the tumor ventral to the tumor without spinal cord tissue. Then, a higher power CO2 laser is used to vaporize the tumor on the surface of the spinal cord tissue by defocusing the laser beam until the tumor is mostly or subtotally resected. Intramedullary nerve sheath tumors are often located in the dorsal aspect of the spinal cord and may be completely within the spinal cord, or partially within the spinal cord and partially outside the spinal cord. After disconnecting the supply vessels from the root artery, the central part of the tumor is also removed first, and then the peripheral part of the tumor is separated and removed until the tumor is completely removed. ⑤ When resecting intramedullary cavernous hemangioma, the grass-green or yellow-white glial hyperplasia band should be cut open to reveal the prune-like purple-black tumor, and then electrocoagulation should be performed to wrinkle the tumor envelope, and the tumor can be free and completely resected smoothly. The demarcation between the glial hyperplasia zone around the tumor and the adjacent spinal cord tissues is not very clear, so the separation of the tumor cannot be carried out between them to avoid damaging the spinal cord tissues. In addition, because small nodular protrusions often occur in the tumor, or small parts of the tumor are separated from the main body of the tumor due to the tumor associated with the emission of blood, so when separating and resecting the tumor, care should be taken to avoid the residual of tiny tumor nodules. (6) When removing intramedullary epidermoid cysts or dermatomal cysts, the soft spinal membrane and tumor envelope are cut at the most superficial part of the tumor, and the tumor contents can usually be removed smoothly. Because of the tight adhesion of the cyst wall to the spinal cord tissue, total excision of the cyst wall is almost impossible. When the huge cyst reaches the ventral soft spinal membrane, the ventral peritoneum of the cyst can be cut open to make the tumor cavity communicate with the subarachnoid space, which can effectively prevent recurrence after surgery. In order to improve the total resection rate of tumor and patient’s survival quality, in addition to the above mentioned techniques, the following matters should be noted: ① When the posterior median vein of the spinal cord hinders the operation, the spinal cord can be incised after electrocoagulation to reveal the tumor so that the operation can be performed in a “bloodless” state; ② In individual patients with glioma, the tumor at the first exploration site may not have a clear boundary. In some patients with glioma, the boundaries of the tumor may not be clear, so do not easily give up the tumor resection, but increase the scope of spinal cord incision or do multi-point exploration, and then separate the tumor to the less clearly demarcated area after the tumor is clearly demarcated, so as to increase the possibility of total tumor resection. (4) A few intramedullary gliomas with off-center growth may cause the spinal cord to rotate and shift, causing the posterior median sulcus to deviate from the midline. (6) When removing an intramedullary tumor invading the medulla oblongata, the intramedullary tumor should be removed first, then the cerebellar hemispheres should be retracted, and if necessary, the inferior cerebellar earthworm should be cut, and the tumor should be separated along the correct tumor interface toward the cephalic end, the posterior median sulcus of the medulla oblongata should be cut, the rods on both sides should be separated, and then the medulla oblongata part of the tumor should be revealed and removed. (8) When the tumor is cystic, the cystic wall contains tumor cells, which should also be removed: along the correct interface, electrocoagulation will crumple the tumor cystic wall and separate it from the soft spinal membrane and the thinned spinal cord tissue, so that the whole tumor can be removed smoothly; (9) When the tumor is huge and it is estimated that one operation is too long to remove it, it can be operated in two stages. The exposure of the second operation should be well articulated to prevent missing or hindering the resection of the whole tumor due to poor exposure of the articulated parts. In addition, the tumor should be cut into a cross-sectional shape during the first operation of the articulation site, so as to facilitate the total resection of the articulation tumor during the second operation; B10. It is difficult to form an ideal separation interface for the resection of recurrent tumors, so the tumor resection is mainly to release the spinal cord compression and relieve the clinical symptoms, and it is not advisable to force the total tumor resection; B11. In the author’s experience, during the operation of intramedullary tumors, about 1/3 of the patients’ tumors have grown to the ventral part of the spinal cord. The spinal cord cavity and medullary cavity secondary to intramedullary tumor will shrink or disappear on their own after total tumor resection, so it is not necessary to resect or perform another cavity shunt. If the spinal cord is still obviously bulging after total tumor resection, the surgeon should gently pull the spinal cord to one side to explore and drain the ventral subarachnoid space to facilitate in situ suturing of the dura mater without tension. The extent of tumor resection is one of the important factors affecting the prognosis, so it is important to judge whether the tumor has been completely resected intraoperatively. In the author’s experience, the signs suggesting total tumor resection are as follows: ① Inflated spinal cord subsidence. If the cavity is not a cavity secondary to the tumor, but a cystic cavity of the cystic tumor, the cystic wall of the tumor must be removed. If the surface of tumor bed is smooth and white or light yellow; if the tumor bed is yellowish green or dark brown and the volume of resected tumor does not match with that shown on MRI, it also indicates cystic tumor and residual tumor cyst wall. ④Intraoperative ultrasound examination can help to identify whether there is tumor residue on the ventral side.