Intramedullary tumors of the spinal cord account for 2%-4% of central nervous system tumors (brain and spinal cord) and 20%-25% of intradural tumors. The incidence of intramedullary tumors in children is higher than that in adults, accounting for approximately 50% of intradural tumors. According to pathological types, 45% of common intramedullary tumors are ventricular meningiomas, 40% are astrocytes, 5% are vascular reticulocytomas, and 10% are other tumors such as lipomas, cavernous hemangiomas, and epidermoid cysts. Before the 1970s, the surgical mortality and disability rates of intramedullary tumors were high, and most neurosurgeons were concerned that removal of intramedullary tumors would aggravate spinal cord injury and cause complications such as postoperative paralysis, respiratory dysfunction, and urinary and fecal disorders, so they generally preferred conservative treatment, often adopting laminar decompression, biopsy, and partial tumor resection, In general, conservative treatment is preferred, which often includes laminectomy, biopsy, partial tumor resection, and radiation therapy. The treatment is usually conservative, with decompression of the vertebral plate, biopsy, partial tumor resection, and radiation therapy. With the introduction of MRI, the preoperative diagnosis has become clearer. Moreover, with the continuous progress of microsurgery technology, the update of surgical instruments, and the intraoperative application of electrophysiological monitoring technology, surgery for spinal cord intramedullary tumors has developed significantly, and surgery has become the only effective method for treating most intramedullary tumors. Common intramedullary tumors of the spinal cord 1. Ventricular meningioma: It is the most common intramedullary tumor in adults, especially in middle-aged people, with the same incidence in both sexes. The cervical segment is the most common site. Most of the ventricular meningiomas in the spinal cord are benign tumors, although there is no envelope, but the boundary between them and the spinal cord is clear, so they can be completely removed during surgery, and can be cured or not recur for a long time after surgery. The incidence of astrocytoma is similar to that of ventricular meningioma after the age of 60. About 60% of intramedullary astrocytomas occur in the cervical medulla or cervicothoracic junction, but are rare in the thoracolumbosacral medulla and conus, and even rarer in the terminal filum. Histologically, astrocytomas of the spinal cord include relatively benign fibrous and hairy cell astrocytomas, ganglioneuroblastomas, and malignant astrocytomas and glioblastomas. Approximately 90% of intramedullary astrocytomas in children are benign, mostly fibrous astrocytomas, while others are hairy cell astrocytomas or ganglion cell tumors. Ten percent of intramedullary tumors in children are malignant astrocytomas and glioblastomas, which have a short history, rapid clinical progression, and easy dissemination of tumors along the cerebrospinal fluid. Fibroblastic astrocytomas predominate in adults, while hairy cell astrocytomas and ganglion cell tumors are rare. About 20% of adult intramedullary astrocytomas are malignant. The boundary between astrocytoma and normal spinal cord is not as clear as that of ventricular meningioma, so total surgical resection is difficult, but with electrophysiological detection, the safety margin of surgery is greatly improved. 3.Vascular reticulocytoma:Also known as hemangioblastoma. Vascular reticulocytoma accounts for about 3%-8% of intramedullary tumors and can occur at any age in adults, mostly around 40 years old, but rarely in children. Vascular reticulocytoma is a benign tumor that originates from blood vessels, has no envelope, but has clear boundaries with the spinal cord, and almost always has soft spinal membrane attachment, and mostly grows in the dorsal or dorsolateral part of the spinal cord. It can be combined with Linda syndrome and cystic lesions of cerebellum or other organs. 4.Other types of tumors: metastatic cancer accounts for 2% of intramedullary tumors, and the low incidence may be related to the small size of the spinal cord and the lack of vascularity. The primary focus is often lung, breast tumor, melanocytoma, etc. There are also reports of fibrosarcoma metastasis to the spinal cord. Other intramedullary tumors include epidermoid cysts, cavernous hemangiomas, lipomas, etc. Clinical characteristics Because of the lack of specific clinical manifestations, early diagnosis of intramedullary tumors is difficult. The course of the disease is usually 2 to 3 years, but the history of malignant and metastatic tumors is very short, a few weeks or a few months. Intratumoral hemorrhage and necrosis can accelerate the disease change. Pain is the most common symptom of intramedullary tumors in adults, while dyskinesia and gait disturbances are more common in children. Pain occurs most often at the level of the spinal cord segment where the tumor is located, but rarely at the radicular level. 30% of patients have sensory and motor disturbances at an early stage. The progression and distribution of symptoms are related to the location of the tumor, with cervical medullary tumors having mainly upper extremity symptoms, typically presenting as unilateral, asymmetric sensory abnormalities. Tumors of the thoracic medulla may have spasticity and sensory disturbances, which often occur in both lower extremities and then develop proximally. Tumors of the lumbar medulla and conus often manifest as pain in the low back and lower extremities, and urinary and fecal dysfunction often appears in the early stage. Radiological examination Due to the introduction of high-resolution MRI, intramedullary tumors are often detected before the appearance of obvious neurological dysfunction, and MRI has become an important tool to confirm the diagnosis of intramedullary tumors, which can not only pinpoint the location, but also clarify the nature of most intramedullary tumors, and can show the cystic changes and spinal cord cavities combined with tumors. If vascular tumor is suspected, DSA can be performed again. Some people believe that surgery for intramedullary tumors will aggravate spinal cord injury and lead to postoperative neurological dysfunction, and advocate that for intramedullary tumors with less serious symptoms, observation and treatment should be carried out first, and surgery should be considered when the neurological function deteriorates progressively. However, a lot of clinical data show that the surgical effect of intramedullary tumors is closely related to the severity of preoperative symptoms. Patients with advanced intramedullary tumors often suffer from severe compression and damage to the spinal cord, and their limbs are close to paralysis or completely paralyzed, so surgery at this time increases the risk of further damage to the spinal cord, and the postoperative effect is poor, and the paralyzed limbs are difficult to recover. Therefore, most scholars believe that early diagnosis and timely surgery are the key to success or failure in the treatment of intramedullary tumors, and the lighter the preoperative symptoms and signs, the better the postoperative recovery, and even the near-normal state can be achieved. Surgery is the most effective method to treat most intramedullary tumors. The extent of surgical resection depends on the boundary between the tumor and the spinal cord. If the boundary is clear, most of them are benign tumors, and the application of modern microsurgery techniques can not only make complete resection, but also have a low disability rate, and often obtain satisfactory results. Almost all ventricular meningiomas, well differentiated astrocytomas, vascular reticulocytomas and spinal cord are clearly demarcated, and surgery should strive for total or sub-total excision. A small incision in the spinal cord to obtain a small amount of tissue for biopsy should be avoided to avoid delaying treatment. For intramedullary malignant tumors, although a major resection or partial resection of the tumor can relieve the disease and reduce the symptoms. However, considering the poor prognosis of intramedullary malignant tumors and the high rate of postoperative disability, it is believed that in such cases, the operation should be terminated only after spinal dissection and histological diagnosis is obtained. For intramedullary dermatomal cysts and epidermoid cysts, it is difficult to completely remove the cyst wall from the spinal cord during surgery, so total excision is not required. It is not possible to completely excise the lipoma in the spinal cord, but it is possible to excise a large part of the tumor, which can also obtain a positive therapeutic effect. Postoperative radiotherapy is still controversial. In the past, many scholars advocated that postoperative radiotherapy should be given to intramedullary tumors. However, in recent years, many studies have shown that most intramedullary ventricular meningiomas can be completely resected and do not recur for a long time, or even cured, so radiotherapy is not necessary for these patients. Radiation therapy is only indicated for patients with malignant ventricular meningioma with little growth and cerebrospinal fluid dissemination metastases. In vascular reticulocytoma, total resection is almost always obtained, and postoperative radiotherapy is not of any value. Intramedullary dermatomal cysts, epidermoid cysts, and lipomas are all benign tumors and do not require postoperative radiotherapy. Most scholars do not advocate postoperative radiotherapy for benign astrocytomas with good intramedullary differentiation, which can cause serious local adhesions and make secondary surgery after recurrence extremely difficult. Radiotherapy is the main treatment for intramedullary malignant astrocytoma, but the average survival time is only 6 months to 1 year. For sub-total resection of benign and malignant adenocarcinoma, the decision of radiotherapy should be based on postoperative clinical and imaging findings. Prognosis The outcome of surgery is related to the patient’s preoperative neurological function and the tumor site. Usually, most patients may have different degrees of sensory loss after surgery, which may be related to the spinal cord midline incision. However, this postoperative sensory deficit can be gradually improved. For patients with severe and long-lasting preoperative neurological deficits, the postoperative recovery was poor and even further aggravated after surgery, while patients with mild preoperative symptoms recovered quickly and with good results after surgery. This shows the importance of early diagnosis and early treatment.