Intraspinal neurilemmoma

　　It is widely believed that the occurrence and growth of intraspinal neurilemmoma are mainly caused by molecular changes at the gene level. Many cancer formations are considered to be due to the loss of normal tumor suppressor genes and the activation of oncogenes. Two types of neurofibromatosis have been extensively studied. Genetic research suggests that the NF1 and NF2 genes are located on the long arms of chromosomes 17 and 22, respectively. Both types of neurofibromatosis are inherited as autosomal dominant with high penetrance. The incidence of NF1 is approximately 1 in 4000 births, half of which are sporadic cases caused by new mutations. In addition to neurofibromas, the clinical manifestations of NF1 include cafe-au-lait spots, skin nodules, skeletal abnormalities, subcutaneous neurofibromas, plexus neuropathy, and concurrent with certain common childhood tumors, such as optic nerve and hypothalamic gliomas, ependymomas. Intraspinal neurofibromas are much less common than those occurring outside the spinal canal. The neurons encoded by the NF1 gene belong to the GTPase activating protein family of molecules (220-KD). GTP proteins are activated by their ligands to participate in the downregulation of the ras oncogene. It is currently inferred that NF1 gene mutations lead to the formation of variant gene products, which cannot effectively induce GTP hydrolysis, thereby promoting the upregulation of the ras gene, strengthening the signal of the growth factor pathway, and ultimately leading to the appearance of characteristic products of NF1 tumors, forming NF1 tumors.

　　Spinal nerve sheath tumorThe course is usually longWhen the tumor undergoes cystic degeneration or hemorrhage, it presents as an acute process.. . If surgical treatment is performed, the following complications may occur:

　　1. Epidural hematoma:Incomplete hemostasis of paravertebral muscles, vertebral bones, and dural venous plexus can lead to hematoma formation after surgery, which can cause exacerbation of limb paralysis. This usually occurs within 72 hours after surgery, and can occur even with the placement of a drainage tube. If this phenomenon occurs, it should be actively explored, the hematoma should be removed, and hemostasis should be carried out thoroughly.

　　2. Spinal cord edema:It is often caused by spinal cord injury during surgery, with clinical manifestations similar to a hematoma. Treatment is mainly based on dehydration and hormones, and severe cases may require reoperation and opening of the dura mater.

　　3. Cerebrospinal fluid leakage:This is often caused by loose suture of the dura mater and muscle layer. If there is drainage, the drainage tube should be removed in advance. For those with slight leakage, change the dressing and observe; for those with persistent leakage or severe leakage, the fistula should be sutured in the operating room.

　　4. Wound infection and dehiscence:Patients with poor general condition, poor wound healing ability, or cerebrospinal fluid leakage are prone to occur. Intraoperative attention should be paid to aseptic operation. After surgery, in addition to antibiotic treatment, it is necessary to actively improve the overall condition, especially the supplementation of protein and various vitamins.

　　The course of intraspinal neurilemmoma is usually long, with the shortest history in the thoracic segment, and longer in the cervical and lumbar segments. Sometimes, the course can exceed 5 years. When the tumor undergoes cystic degeneration or hemorrhage, it presents as an acute process.

　　The most common initial symptom is radicular pain, followed by sensory abnormalities and motor disorders. The pain from tumors in the upper cervical segment mainly occurs in the neck, occasionally radiating to the shoulder and upper arm. The pain from tumors in the neck-thoracic segment is often located at the back of the neck or upper back, and radiates to one or both shoulders, upper limbs, and chest. Tumors in the upper thoracic segment often manifest as back pain, radiating to the shoulder or chest. The pain from thoracic tumors is often located in the thoracic-lumbar region, and can radiate to the abdomen, inguinal area, and lower limbs. The pain from thoracic-lumbar tumors is located in the lumbar region, and can radiate to the inguinal area, arm, thigh, and lower leg. The pain from sacral tumors is located in the sacral and gluteal regions, perineum, and lower limbs.

　　About 20% of patients present with atypical symptoms as the initial manifestation, which can be divided into two types: hyperesthesia and hypoesthesia. The former is characterized by sensations of crawling, numbness, coldness, acid and swelling, and burning. The latter is mostly a combined decrease in pain, temperature, and tactile sensation.

　　Motor disorders account for the third most common initial symptom, and due to the different locations of the tumor, they can cause radicular or fascicular damage leading to motor disorders. With the progression of symptoms, there may be dysfunction of the pyramidal tract, resulting in varying degrees of paralysis and severity.

　　The main clinical symptoms and signs of spinal nerve sheath tumors are pain, sensory abnormalities, motor disorders, and sphincter dysfunction. The incidence of sensory abnormalities is about 85%, and the incidence of pain is nearly 80%.

　　Sensory disorders generally start from the distal part and gradually develop upwards. Patients may have subjective sensory abnormalities in the early stage, with no special findings on examination. Subsequently, there may be sensory impairment, and finally, all sensations are lost along with motor function. Since there is no spinal cord substance in the conus and cauda equina, sensory abnormalities are distributed in a peripheral nerve pattern, with the typical symptom being anal and perineal skin numbness in the saddle area.

　　Most patients come to the hospital with varying degrees of difficulty in movement, with half of the patients having limb paralysis. The time of onset of motor disorders varies depending on the location of the tumor. Tumors in the conus or cauda equina may only show obvious motor disorders in the late stage, while tumors in the thoracic segment may appear symptoms earlier.

　　Dysfunction of the sphincter function is often a late symptom, indicating partial or complete compression of the spinal cord.

　　Intraspinal nerve sheath tumors originate from the dorsal spinal nerve root and can also produce subdural infiltration when they grow concentrically. This situation is more common in cases of neurofibroma. There is no special preventive method for intraspinal nerve sheath tumors, and the main approach is to discover the condition in time and take surgical treatment, actively exercise, and improve personal physical fitness.

　　Since spinal nerve sheath tumors often occur in the subarachnoid space, the growth of the tumor is more likely to cause obstruction of the subarachnoid space, so the lumbar puncture pressure neck test often shows varying degrees of subarachnoid space obstruction. Due to the obstruction of the subarachnoid space, the cerebrospinal fluid circulation below the site of the tumor is obstructed, and tumor cells may fall off, causing an increase in cerebrospinal fluid protein content. Additionally, because the tumor is generally more free within the spinal canal, symptoms can worsen after lumbar puncture, which is due to the dynamic changes within the spinal canal cavity causing increased compression on the spinal cord.

　　1. Spinal X-ray:The direct sign is the shadow of calcification spots of the nerve sheath tumor, which is less common. The indirect sign refers to the corresponding changes caused by the compression of the spinal canal and adjacent bony structures by the tumor, including destruction of the vertebral arch, widening of the distance between the vertebral arch roots, even complete destruction and disappearance of the vertebral arch roots, concave vertebral bodies, or enlargement of intervertebral foramina.

　　2. Myelography:The rate of complete subarachnoid obstruction is about 95% or more, typically presenting as a cup-shaped filling defect.

　　3. CT and MRI:It is difficult to make an accurate diagnosis by CT scan, as the tumor appears as an extramedullary hypointense focus on the T1-weighted MRI image. On the T2-weighted image, it appears as a hyperintense focus, and after enhancement, the solid tumor shows uniform enhancement. Cystic tumors show ring enhancement, and a few tumors show uneven enhancement. Additionally, depending on the anatomical level of the tumor, there may be corresponding spinal cord displacement.

　　Patients with intraspinal nerve sheath tumors should have a light diet, eat more vegetables and fruits, rationally match the diet, and pay attention to adequate nutrition. Patients should also avoid smoking and drinking, and avoid spicy, greasy, and cold foods.

　　The treatment of benign nerve sheath tumors is mainly surgical resection. The vast majority of cases can be cured by standard posterior laminectomy, complete resection of the tumor, and then achieving cure. If the tumor is completely resected, recurrence usually occurs rarely. The vast majority of nerve sheath tumors are located on the dorsal or lateral side of the spinal cord, and they are easily seen after the dura is opened. Tumors located on the ventral side may require the incision of the dentate ligament to obtain sufficient exposure. Tumors in the lumbar region may be covered by the cauda equina or conus medullaris. In these cases, the nerve roots need to be separated to provide sufficient exposure, and the tumor usually compresses the cauda equina or conus medullaris to one side. After sufficient exposure is obtained, the interface between the tumor and the nerve or spinal cord is easily identifiable. There is usually an arachnoid layer closely adhering to the tumor, which is a porous structure, independently surrounding the dorsal and ventral nerve roots. Sharp dissection is performed during surgery to dissect and separate the tumor, and coagulation is applied to the surface of the cyst wall to reduce the volume of the tumor. The nerve roots connected to the proximal and distal ends of the tumor must be cut to ensure complete resection of the tumor. If the tumor is large, it can be first resected intra-cystically, decompressed, and the nerve roots originating from the tumor must be cut. Occasionally, some small branches of the nerve roots can be preserved, especially for smaller tumors. Cutting these nerve roots rarely causes severe neurological deficits, even at the level of cervical and lumbar enlargement, as the function of these nerve roots is usually compensated by adjacent nerve roots. Some tumor tissue may be embedded in the spinal cord meninges, and compress the spinal cord. In these cases, the interface between the tumor and the spinal cord is usually difficult to separate, and partial resection of the meningeal tissue can achieve complete resection of the tumor.

　　When a tumor significantly invades the paravertebral structures through the intervertebral foramen, special treatment should be performed during surgery. The preoperative extension of the subdural tumor should be carefully analyzed to facilitate the accuracy of the surgical approach. Magnetic resonance imaging can usually provide a detailed understanding of the adjacent structures of the tumor. However, for dumbbell-shaped tumors, CT scanning after myelography will be more sensitive, which is convenient for observing the spinal canal and paravertebral structures.

　　Tumors in the paravertebral region of the neck are usually difficult to reach through the anterior cervical approach, as the anterior cervical vascular and nerve structures are rich, such as the brachial plexus, posterior cranial nerves, and vertebral arteries, etc. The mandible and its associated craniocervical musculoskeletal structures further limit the exposure of the upper cervical spine. Fortunately, the vast majority of dumbbell-shaped tumors can be resected by expanding the posterior cranial exposure. A midline incision combined with standard laminectomy can safely resect tumors extramedullary within the spinal canal. The total resection of one side of the joint surface, up to 3cm (from the dura edge to the paravertebral region), can increase the paravertebral exposure. The vertebral artery usually shifts forward and medially, and the vertebral artery and its tumor can be well protected by subperiosteal dissection. Although the stability impact caused by the resection of one side of the cervical joint surface is difficult to judge, unilateral laminectomy can significantly reduce the destruction of vertebral stability.

　　The expansion of chest tumors to paravertebral areas usually forms large masses that invade the thoracic cavity. Standard posterior approaches are difficult to provide sufficient vision to handle the lesions in front of the paravertebral area. Anterior thoracotomy or extrapleural thoracotomy can expose the anterior vertebral structures well. If subdural exposure is necessary, postoperative cerebrospinal fluid pleural leakage may occur. This is mainly due to the negative pressure in the pleural cavity and the postoperative closed pleural drainage may worsen cerebrospinal fluid effusion. The combined anterior and posterior approaches can increase exposure and can be performed in stages. The lateral extrapleural approach is very valuable for cases that require simultaneous increase in intramedullary and paravertebral exposure, usually composed of a baseball bat-like incision, ensuring the traction of paravertebral muscles. The superficial thoracic scapular muscles are stripped off at the midline and then rotated laterally along the skin flap, exposing the paravertebral muscles longitudinally. These muscles should be stripped from the posterior accessory structures of the spine and the ribs. Rib resection and pleural decompression can increase the exposure of the extrapleural paravertebral area. Intramedullary exposure can be obtained through the standard laminectomy of the paravertebral muscles. Since it does not enter the pleural cavity, cerebrospinal fluid leakage is rare. The lumbar dumbbell-shaped tumor can also be accessed through a lateral approach, at this level, the thoracodorsal fascia can be cut along the skin incision and pulled laterally. The lumbar paravertebral muscles are very deep, and the tumor is often buried within the psoas major muscle. It is difficult to completely resect the tumor through a retroperitoneal approach alone, because the psoas major muscle fibers and the connective tissue at the tumor edge are difficult to differentiate. The lumbar plexus nerve roots and their branches, including the femoral nerve, pass through the surface of the psoas major muscle, are difficult to identify, and are easily damaged during the posterior peritoneal dissection. The lateral extraperitoneal approach can ensure that the tumor and the psoas major muscle are traced through the intervertebral foramen, all dissections are performed on the surface of the tumor, allowing the nerves to be identified from the proximal end, thereby further reducing nerve injury. Intramedullary subdural tumors can be easily resected through the standard laminectomy. Sacral dumbbell-shaped tumors usually require anterior and posterior exposure, maintaining a lateral position, allowing for staged surgery or simultaneous surgery in one stage.