Diagnosis and differential diagnosis of spinal metastatic carcinoma

Patients suspected of spinal metastatic cancer should be thoroughly diagnosed and examined, including medical history and physical examination. Warning signals include symptoms of spinal injury (nocturnal pain, neurological dysfunction, gait instability) and systemic symptoms (weight loss and organ failure). Investigate the patient's smoking history, environmental or occupational exposure history and travel history. Counseling should include situations that may increase the possibility of cancer (HIV, inflammation and cancer in situ) as well as recent cancer screening and family history. Detection of blood cell count, biochemistry, prostate specific antigen, considering multiple myeloma, increase plasma and urine protein electrophoresis analysis. 1.x-ray plain film: It has long been the main evaluation method for patients with new symptoms related to spine, mainly because of its simple technology, low price and wide application. Therefore, X-ray plain film has become an effective screening and detection tool to confirm soluble and sclerosing injuries, pathological fractures, spinal deformities and masses. Breast cancer and prostate cancer can cause sclerosing injury, but most metastatic cancers of the spine are soluble, and X-ray plain films can't show the relevant changes before more than half of the vertebral bodies are involved. Because of this relative insensitivity, definite diagnosis often needs to be combined with other imaging techniques. Radionuclide scanning (bone scanning) is a sensitive method to identify areas with increased metabolic activity in the skeletal system. Before 30-50% of vertebral bodies were involved, X-ray plain films could not show tumor-related changes, but bone scanning could find metastatic tumors earlier with a resolution of 2 mm It is reported that the sensitivity of radionuclide bone scanning in detecting metastatic carcinoma of spine is 62-89%. However, because radionuclide scanning detects enhanced metabolic activity, inflammation or infection can also enhance metabolic activity, so it is not specific for metastatic lesions. Low image resolution hinders the effect of scintigraphy. Benign manifestations should be excluded by combining ct or MRI images, and surgical exploration should be carried out if necessary.

2.SPECT (Single Photon Emission CT): It is a more advanced radionuclide bone scanning method, providing 3D images of suspected spinal metastatic cancer. This technique has more detailed images and higher sensitivity and specificity than plane scanning. In addition, unlike other examination techniques, SPECT images can distinguish metastatic lesions from benign lesions. SPECT is an effective and relatively cheap detection tool when planar scanning can not diagnose spinal metastatic cancer. Positron emission tomography (PET) using fluorodeoxyglucose (FDG) as tracer is also a general monitoring tool for detecting metastatic lesions and tumor staging. PET equipment has been proved to be superior to planar scintigraphy in finding metastatic carcinoma of spine. Because the metabolic activity of tumor is directly measured, rather than an indirect sign of bone transformation, early detection of tumor can be realized. PET scanning is also used to distinguish cystic and necrotic areas of tumors. This information can improve the diagnostic rate of biopsy sampling and help to make surgical intervention plans. However, the resolution of PET is limited, so it must be combined with CT or MRI images. In addition, PET scanning is time-consuming and expensive. The latest generation of multi-slice CT scanning equipment provides very detailed images of spinal skeleton anatomy and tumor invasion. The increased sagittal and coronal digital reconstruction further improves the details of CT images. Combined with CT images, myelography can obtain a high-precision representation of the space occupied by neurons to identify the compressed structure, which is helpful to clarify the causes of spinal cord compression and to understand whether the tumor invades the spinal canal or the fracture piece of pathological fracture protrudes backward into the spinal canal. Because of the thorough identification of local anatomical structure, CT examination is of great value in formulating surgical intervention plan, which can help guide surgical approach, surgical method and determine internal fixation range. For patients who are suspected of metastatic cancer of the spine and cannot determine the primary focus, CT scan of the main body cavity should be performed in addition to the affected part of the spine to determine the primary focus of the tumor. In addition, CT angiography can evaluate the blood supply and reflux of spinal metastatic cancer.

3. Magnetic resonance imaging: It is considered as the gold standard imaging equipment for evaluating spinal metastatic cancer. When detecting spinal lesions, MR images are more sensitive than standard X-ray plain films, CT and radionuclide scanning. This sensitivity is largely due to the excellent resolution of MR images on the soft tissue structure of the spine, including intervertebral disc, spinal cord, nerve roots, spinal membrane, spinal muscle groups and ligaments. MR images can show the boundary between bone and soft tissue, and provide anatomical details of tumor invasion or compression of bone, nerve and paraspinal structures. A set of MR images includes weighted images of T 1 and T2 on three standard axes (axial, sagittal and coronal) after contrast agent application. In addition, because the fat in bone marrow is a high intensity signal in T 1 weighted images, the study of fat inhibition can further explain the principle of signal enhancement in spinal bone tissue. Although diffusion-weighted imaging is unconventional, it can distinguish pathological and non-pathological compression fractures.

4. Traditional digital subtraction angiography (DSA) is an important tool to evaluate metastatic carcinoma of spine. For patients with metastatic tumors whose primary tumors (nephroblastoma, thyroid adenoma, angiosarcoma, leiomyosarcoma, hepatocellular carcinoma and neuroendocrine tumor) are rich in blood supply, it is of great significance to know the blood supply of metastatic tumors if surgery is considered. Angiography can also be used for preoperative embolization of metastatic tumors, which is an effective treatment for patients who cannot be operated. After embolization, the amount of intraoperative bleeding can be reduced, which is helpful for the complete resection of the lesion. In addition, controlling intraoperative bleeding and reducing the blood supply of metastatic tumor may shorten the operation time and prevent incision dehiscence and nerve tissue degeneration caused by postoperative hematoma. 1. Active treatment of primary cancer: If primary cancer exists, is untreated, or recurs after treatment, it is necessary to actively treat primary cancer, otherwise the curative effect of metastatic tumor will be affected, and new metastatic focus may appear. If no primary cancer is found, it should be actively sought and treated.

2. Comprehensive treatment of metastatic tumor:

(1) Chemotherapy: Different types of tumors have their own sensitive chemotherapy drugs. The most common breast cancer metastasis, hormone therapy is mostly effective. Some single drugs, such as 5- fluorouracil, adriamycin and cyclophosphamide, have certain curative effects, but combined chemotherapy is better. Chemotherapy for spinal metastatic cancer can relieve or alleviate pain, but the effect is not lasting.

(2) Radiotherapy: No matter single or multiple metastases, local radiotherapy can be performed to inhibit tumor growth and relieve symptoms.

(3) Hormone therapy: Some cancers are related to endocrine, such as breast cancer and prostate cancer, which are related to female and male hormones, and can be treated with hormones.

(4) Immunotherapy: Interferon is effective for some cancers. If combined with chemotherapy and radiotherapy, the effect is better. Even some cavity parts can be injected locally.

(5) Surgical treatment: The purpose is to improve the quality of life by effective survival, such as relieving symptoms, stabilizing the spine, improving paralysis and prolonging life.

3. Symptomatic support treatment: No matter whether the comprehensive treatment is effective or not, some symptoms appear in a period of time and need symptomatic treatment, such as giving sedatives and appetizers, infusion and blood transfusion, supplementing nutrition and vitamins, maintaining water-electrolyte balance and improving organ function.

4. Surgical treatment and patient selection

Advances in drug research and development have improved the treatment of many tumors and prolonged the survival of many patients. The treatment decision of this kind of patients needs to refer to the most valuable literature, doctors' clinical expertise and experience, and consider the patients' wishes, of which the latter two contents are the key, and the patients' wishes are particularly important because of palliative treatment. In fact, clinicians should mainly consider three aspects when making treatment decisions: patient factors, spinal stability and neurological function.

In the past 20 years, surgical technology has been developing continuously. In the case of acceptable complications, anterior and posterior spinal stabilization has improved the scope of decompression and tumor resection. Some patients can get long-term disease-free survival, especially those with single renal cell malignant tumor, but for most patients, the purpose of surgical treatment is to preserve neurological function, relieve pain and ensure the mechanical stability of the spine. Before considering the surgical treatment of spinal metastatic cancer, most clinicians usually expect the survival time of patients to exceed 3 months. Surgical indications: 1. Single metastatic tumor with unknown primary focus should be operated at the same time as frozen biopsy; 2. Recurrence or aggravation after chemotherapy or radiotherapy; 3. It is known to be radiation resistant; 4. Paraplegia or spinal instability.

Selecting patients with surgical indications is a challenging task. Tokuhashi and others developed a scoring system based on the types of primary tumors, the number of spinal metastases, the manifestations of extraspinal and visceral metastases, the general condition of patients and the state of nervous system. The better the prognosis index (low invasive tumor, single spinal lesion, no metastasis from other parts, good overall condition and no neurological dysfunction), the higher the value of surgical treatment. When the patient's score is greater than 9, surgical resection of the lesion is recommended. When the patient's score is less than 5 and the prognosis index is poor, palliative therapy, that is, restrictive decompression and fixation, is suggested. The progress of surgical technology and the expansion of treatment options prompted Tomita and others to develop a similar scoring system according to the classification of primary cancer, the manifestations of visceral metastasis and the number of bone metastases. In this system, the better the prognosis index, the lower the score. For patients with scores of 2-3, extensive or marginal resection should be performed with long-term local control as the goal. Patients with 4-5 points indicated that the mid-term should be controlled, and the edge of the lesion or resection within the lesion should be performed. Palliative surgery is recommended for patients with 6-7 points, and supportive therapy is only applicable to patients with 8 points or more. The principle of establishing this scoring system is to assist surgeons to select patients who can benefit from surgical treatment and determine the reasonable range of surgical resection. In fact, calculating the scores of Tomit and Tokuhashi systems will not limit the choice of treatment methods, especially other treatment methods such as the newly developed SRS. However, the basic principles of these prognostic scoring systems still apply. In addition, once the patient is considered suitable for surgical treatment, it is required to have a comprehensive understanding of the anatomical and histopathological characteristics of metastatic tumor and its adjacent structures, biomechanics of the spine and the changes caused by metastatic tumor when deciding the surgical approach and fixation method.

Second, the mode of operation

Surgical anatomy and histopathological tumor classification: The surgical resection and decompression methods of patients with spinal metastatic cancer mainly depend on the involved spinal segment, the position of the tumor in the spine, the histological characteristics of the tumor and the type of spinal reconstruction needed. Vertebral body is the most common involved part of spinal metastatic cancer. Anterior surgery can effectively remove the focus and decompress the spinal canal. However, this method increases the incidence and mortality of surgery-related complications. Therefore, posterior or posterolateral transpedicular approach is the first choice. Through this approach, three-column decompression and internal fixation can be completed, which is more and more used in thoracolumbar spine, especially in circular resection and/or multi-segment resection of vertebral body.

1. Treatment of spinal instability secondary to spinal metastatic cancer

In the past, there was no clear definition of spinal instability secondary to spinal metastatic cancer. A review shows that there is no clear treatment guideline for cervical or thoracolumbar instability that is about to occur or has already occurred. At present, its diagnosis depends on a set of clinical and imaging parameters, which have not been verified. Biomechanical study of spine shows that more than 80% of the support of vertebral body comes from the axial load of spine. Therefore, the vertebral body, the most common site of metastatic tumor, has a significant impact on the bearing capacity of the spine. The degree of influence depends on the volume of the lesion, the cross-sectional area of the intact vertebral body and the total bone mineral density. With the increase of soluble lesion volume, the integrity of vertebral body is destroyed, leading to compression or burst fracture. Fractures or tumor fragments produced by these fractures enter the spinal canal or intervertebral foramen, causing compression of nerve structures, leading to pain or motor/autonomic nerve dysfunction. Studies have shown that 50-60% of thoracic vertebrae and 35-45% of lower thoracic vertebrae/thoracolumbar vertebrae are dissolved lesions, indicating that vertebral collapse has occurred. Segments with high mobility or high pressure, such as cervicothoracic segment and thoracolumbar segment, can be fractured under a small tumor load. The metastasis of dorsal structure of spine, especially articular process, is considered as the cause of pathological dislocation, spondylolisthesis and horizontal instability. Because the incidence of metastatic tumors in the posterior part of the spine is much lower than that in the vertebral body, this lesion is not common.

Understanding the manifestations and characteristics of instability is helpful to choose surgical methods and determine the scope of reconstruction. Because of the different injury mechanisms, the indications of internal fixation and decompression of spinal instability caused by tumor formation are not clear. Cybulski suggested using the following imaging criteria to evaluate spinal instability caused by tumor: 1. Front column destruction (vertebral collapse >; 50%); 2.2 or more adjacent vertebral bodies collapse; 3. The tumor involves the middle and posterior column (there is the possibility of shear deformity in the rear); 4. Laminectomy was done before, and no anterior column lesions were found. These studies show that when one of these unstable criteria exists, or life expectancy is greater than: when patients with 5-6 months have symptoms of nerve compression, good immune or nutritional status, incomplete neurological dysfunction, tumor is not sensitive to chemotherapy, and tumor in previous treatment fails, feasible surgery is recommended for internal fixation.

2. Treatment of spinal cord compression

Metastatic epidural spinal cord compression (MESCC) occurs when tumor tissue or fracture piece protrudes into spinal canal. When this lesion leads to nerve damage, it is usually a surgical emergency. 5- 10% cancer patients and more than 40% patients with bone metastasis in other parts will have this situation. Corticosteroids and X-ray radiotherapy are the main treatment methods. In the past, the choice of surgical methods was limited to laminectomy, but this technique could not decompress the front of the vertebral body, making the posterior structure unstable, leading to spinal instability, neurological deterioration and pain. Therefore, the active surgical technique of spinal cord annular decompression is more commonly used.

A review shows that with the development of time, the improvement of clinical results is related to the progress of more and more active surgical treatment strategies. Although the postoperative mortality is relatively high (average 10%), the best report on the improvement of motor function still comes from the study of patients with anterior decompression and internal fixation (average 75%). Other studies have shown that XRT surgery is superior to XRT alone in the choice of treatment methods for MESCC. Although the results of this study are impressive, it is important to consider the selection criteria of the study. It is worth noting that tumor patients who are highly sensitive to radiotherapy, such as lymphoma, myeloma and small cell lung cancer, are excluded from the two groups. Among these patients, simple XR T is suitable for MESCC patients without spinal instability. In addition, pure XTR is also suitable for patients with rapid neurological dysfunction, no obvious bone protrusion in the spinal canal, or patients with expected survival time.

Drug therapy applied to the treatment of spinal metastatic cancer can be divided into two categories: drugs that directly act on tumors and drugs that minimize secondary symptoms of tumors. Except for some chemotherapy-sensitive tumors, such as Ewing's sarcoma, osteosarcoma and neuroblastoma, many spinal metastatic cancers are not very sensitive to cytotoxic drugs, and anticancer drugs for these diseases are limited. On the contrary, drugs to prevent and improve the symptoms of spinal tumors (including pain, inflammation and bone destruction) are widely used.

2. Chemotherapy

Although the progress of chemotherapy schemes has improved the therapeutic effect of cancer in the past decades, these therapies usually have limited effect in the treatment of spinal metastatic cancer, because spinal metastatic cancer is a late complication of cancer. The application of neoadjuvant therapy after operation has improved the therapeutic effect of some metastatic tumors, including germinoma, high-risk neuroblastoma, Ewing's sarcoma, osteosarcoma and so on. In addition, tumors that were once considered unresectable can be surgically removed after receiving neoadjuvant therapy. For example, because of the high incidence of surgical complications and limited postoperative improvement effect, it used to be considered that spinal metastasis of non-small cell carcinoma in the superior sulcus of the lung could not be surgically removed. However, after receiving neoadjuvant therapy (etoposide and cisplatin) and XRT, two-thirds of patients with this tumor found that the tumor volume decreased and the possibility of negative margin resection increased during surgery. Other drug therapies are also effective in the treatment of spinal metastatic cancer.

3. Hormone therapy

Some metastatic cancers of the spine, especially breast cancer and prostate cancer, may have hormone receptors, and direct treatment of these receptors is effective. Selective estrogen receptor modulators, such as tamoxifen, aromatase inhibitors, such as letrozole, anastrozole and exemestane, have shown their effectiveness in the treatment of breast cancer. For prostate cancer, estrogen inhibitor combined with gonadotropin-releasing hormone agonist and/or flutamide is an effective treatment. Even if the primary tumor is sensitive to hormone therapy, the metastatic tumor may not have the same hormone receptor, so it may not be sensitive to hormone therapy.

4. Diphosphate therapy

These drugs can inhibit bone destruction and bone resorption related to spinal metastatic cancer, reduce the risk of pathological fractures, relieve local pain caused by soluble lesions, and reduce hypercalcemia related to malignant tumors. The treatment of metastatic breast cancer, multiple myeloma and other osteolytic metastases has been proved to be effective.

5. Corticosteroid therapy

Corticosteroids are the basic drugs to treat the pain related to spinal metastatic cancer and acute neurological dysfunction caused by the compression of spinal cord by metastatic tumor focus. Corticosteroids can relieve inflammation and tumor-related pain. It can also relieve spinal edema and improve short-term neurological function. Finally, it can also directly dissolve tumors, such as lymphoma, multiple myeloma, breast cancer and so on. However, there is no consistent view on the dosage scheme of corticosteroids, that is, high dose and relatively low dose. The study showed that there was no difference in pain, walking and bladder function between the initial intravenous dose of 100mg and 100mg.

6. painkillers

Spinal metastatic cancer can cause severe mechanical or neuropathic pain, so analgesia has become one of the main goals of many treatment schemes. Pain caused by cancer can lead to depression, anxiety and fatigue if it is not handled properly. Despite continuous efforts to improve the route of administration of painkillers, inappropriate cancer pain still exists. The treatment of cancer pain is usually gradual, including non-steroidal anti-inflammatory drugs, weak opioids and powerful morphine analgesics. The first-line drugs should be non-opioid analgesics, such as acetaminophen and aspirin. The American Pain Association recommends the combination of long-acting and short-acting opioids and the use of laxatives to avoid the use of pethidine. Morphine should be taken orally before intravenous injection, including axonal analgesics. This step therapy is combined with adjuvant therapy to prevent the side effects and neurological complications of analgesics. In addition, many patients with metastatic cancer of the spine suffer from neuropathic pain due to involvement of paravertebral plexus. This kind of painful opioid is difficult to treat, so other countermeasures are needed, including continuous nerve root block through indwelling catheter or cryoablation with anesthetic. Other drugs may also be effective in treating neuropathic pain, including anticonvulsants, neuroleptics and lidocaine patches. These analgesics can cause uncontrollable side effects, so it is necessary to monitor them during taking and give corresponding treatment. Opioid analgesics usually cause gastrointestinal symptoms, including constipation and nausea. When using these drugs, laxatives and antiemetics should be given appropriately. Opioid drugs can aggravate gait disorder and cognitive disorder in elderly patients, so safety precautions are necessary. Patients who use opioids for a long time may be dependent on their bodies, and sudden withdrawal of opioids should be avoided. Anticonvulsants can cause drowsiness and dizziness, while antipsychotics can cause sedation, anticholinergic effects, postural hypotension and weight gain. It is necessary to monitor the side effects, pain relief effect, functional status and quality of life parameters of patients receiving cancer pain treatment.

7. Radiotherapy

Radiotherapy is the main method to treat metastatic cancer of spine, which plays an important role in relieving pain, preventing pathological fracture and stabilizing nerve function. The total dose of XRT is usually 25-40Gy within 10- 14 days. The irradiation level is located at the edge of metastatic focus 5cm, and the upper and lower vertebral bodies are horizontal. Whether local control can be achieved depends on the projection dose of the target lesion and the histological classification of the tumor. However, the traditional XRT is inaccurate, because the nerve structure sensitive to radiation is adjacent to the lesion, so it cannot be used for high-dose irradiation of a single target lesion of the spine. Therefore, the radiation dose to the focal point is usually insufficient. Therefore, the histological type of tumor is that people who resist radiation do not recommend radiotherapy.

Different from the traditional XRT with large-area irradiation, spinal SRS can accurately focus large-dose cross beams on designated targets, and can limit radiation to radiation-sensitive structures such as spinal cord and skin. X-ray dose classification allows a single high-dose irradiation to the target tissue, and SRS can be divided into 1-2 outpatient treatments. Recently, a precision outer frame and an image-guided borderless system have been applied. Image-guided systems use internal or external fiducial markers to provide near-instant updates to the patient's posture to focus the rays and avoid external fixation. Because external fixation is troublesome and will cause discomfort, this technique is especially suitable for the spine. The study of these systems shows good results, including the termination of tumor progression, pain relief and fewer adverse events. The long-term results after focused radiotherapy are very important for accurately evaluating the advantages and disadvantages of this technology. For example, early recording of pathological fractures after SRS treatment has been completed, which may lead to rapid and significant tissue damage due to focused rays. However, highly conformal XRT can be used to irradiate the focus at a high dose while minimizing the exposure range of surrounding tissues, so that the treatment of tumors considered as "radiation insensitive" can continue, and the focus can be selected for re-irradiation. Therefore, the emergence of SRS fundamentally changed the treatment mode of spinal metastatic cancer.

1940 proton beam was first used to treat cancer, but it was not widely used. In the past 20 years, many treatment centers have been equipped with proton beam equipment, which has made it popular in the field of tumor treatment. Different from the X-ray beam and γ -ray beam irradiated by traditional methods and stereotactic methods, proton beam therapy can emit rays to the key structures of the central nervous system with minimal adverse reactions. This is mainly due to the unique physical characteristics of protons, that is, to obtain the maximum energy peak with minimum scattering. Due to the limited utilization and high cost of proton beam therapy, its application in most patients is limited. With the development of this technology in more and more treatment centers, its application will become more and more common.

Although traditional XRT, SRS and proton beam therapy can control local lesions, preserve nerve function and relieve pain, these therapies cannot correct spinal instability and deformity caused by metastatic tumors and the pain and dysfunction caused by them, nor can they alleviate spinal cord compression caused by pathological fractures and fracture pieces protruding into spinal canal or nerve root canal. When XRT is used as adjuvant therapy or neoadjuvant therapy in surgery, its application opportunity must be carefully considered. The adverse consequences caused by XRT include poor healing of wounds and bone grafts after surgical reconstruction. Therefore, it is recommended to start radiotherapy 3-4 weeks after operation.

8. Percutaneous kyphoplasty

Extensive and multiple metastatic cancers of the spine have traditionally been treated conservatively, including traditional XRT, corticosteroids, analgesics, wearing orthopedic stents and bed rest. However, the obvious pain relief and bone enhancement after XRT treatment did not exceed 2 weeks and 4 weeks respectively. Although kyphoplasty has been used to treat diffuse hemangioma of vertebral body, it has become an effective treatment for pathogenic fractures caused by spinal metastatic cancer.

Vertebroplasty is completed by injecting bone cement directly into the vertebral body, while kyphoplasty is to place an inflatable balloon in the vertebral body and expand it to form a cavity, and then inject bone cement. The application of balloon dilatation in kyphosis plasty can improve kyphosis caused by vertebral collapse and show its effect of preventing kyphosis from worsening. Injecting bone cement into collapsed vertebral body has been proved to be effective in relieving pain. It can be assumed that the relief of mechanical pain is due to the correction of kyphosis, but it may also be that bone cement has analgesic effect. The indication of kyphoplasty in the treatment of metastatic spinal cancer is gradually taking shape recently. This technique has been proved to be a safe and effective measure to treat the pain of vertebral fracture caused by metastatic tumor. When combined with XRT, it can relieve the pain of patients who are considered to have no surgical indications. However, spinal cord compression caused by pathological fracture is a relative contraindication of kyphoplasty, because this technique can not relieve the compression of nerves, but forces the fracture to penetrate into the spinal canal and aggravate the spinal cord compression. The complications of this operation are rare, usually including leakage and dislocation of PMMA, causing compression of neural structure or pulmonary embolism. Although kyphoplasty is an effective method to treat the pain of spinal metastatic diseases, it has limited effect in stabilizing the spine, correcting deformity and relieving spinal cord compression, and can be properly handled through surgical decompression and internal fixation.

9. Intramedullary metastatic tumor of spinal cord

Intramedullary metastatic tumor of spinal cord (ISCM) is a rare case, and about 2% of tumor patients found this disease at autopsy. In these cases, about 5% patients were diagnosed with systemic diseases before they died. The most common source of ISCM is lung cancer, especially small cell lung cancer. Intramedullary metastasis rarely occurs in tumors that usually metastasize to the spine, such as breast cancer and prostate cancer, lymphoma, melanoma and renal cell carcinoma. Because it is difficult to distinguish symptoms from clinical manifestations, it is difficult to distinguish intramedullary metastases from other diseases (such as epidural metastases and tumor-like necrotizing myelopathy). For patients with a history of malignant tumor, ISCM should be considered when a limb loses motion or sensation, because asymmetric spinal cord function is often suggested as intramedullary tumor. In addition, it is estimated that 30-45% of ISCM patients develop Brown-Secard syndrome or pseudo-Brown-Secard syndrome. Intramedullary metastasis is marked by rapidly progressing neurological symptoms, while typical primary intramedullary tumors progress slowly and show progressive symptoms. About 75% of patients with intramedullary metastasis have completely lost neurological function within 65 0 months after the onset of neurological symptoms. In addition, muscular atrophy is a common sign of primary intramedullary tumor, but it is not common in patients with intramedullary metastasis.

Intramedullary metastasis is usually found late, and patients often have metastasis from other systems. Therefore, the development of intramedullary metastasis is usually related to poor prognosis. Without treatment, the average survival time is less than 1 month. Therefore, many authors advocate using XRT instead of surgical resection. Radiotherapy is an effective treatment for some radiation-sensitive tumors, such as small cell lung cancer or breast cancer and lymphoma, but it is ineffective for radiation-resistant metastatic tumors. For such patients, minimally invasive surgical resection combined with the treatment of primary tumor and other secondary metastatic tumors may be helpful to stabilize or reverse neurological dysfunction, prolong the survival time and improve the quality of life of patients. The tumor can be resected by CO2 laser vaporization, which is simple to operate and can reduce the traction on the spinal cord. In addition, intramedullary metastases are usually isolated and well-defined masses, and standard minimally invasive surgery is easy to remove.