Intradural nerve sheath tumors, also known as intravertebral Schwann cell tumors, account for about 25% of intradural spinal tumors. They can occur in all segments of the spinal canal, are mostly solitary, and have a peak incidence between the ages of 40 and 60 years, with no significant difference between male and female genders. Intravertebral nerve sheath tumors originate from dorsal spinal nerve roots and may produce subchondral infiltration when growing centripetally, which is more common in cases of rhombomatous neurofibromas. Nerve sheath tumors of the brachial or lumbar plexus may grow along multiple nerve roots into the dura mater. In contrast, paraspinal syringocytomas usually lie outside the dura mater as they expand into the spinal canal. Approximately 2.5% of intradural nerve sheath tumors are malignant, and at least half of these occur in patients with multiple neurofibromatosis. The exact cause of tumor formation remains unclear, and there is considerable agreement that tumor development and growth are primarily due to molecular alterations at the genetic level. The vast majority of intravertebral nerve sheath tumors are located entirely within the dura mater, with 10% to 15% growing out of the spinal canal through the dorsal nerve root cuffs to form a dumbbell-shaped tumor; about 10% of nerve sheath tumors are located outside the dura mater or in the paravertebral region; and about 1% of nerve sheath tumors are intramedullary in nature, and are thought to grow along the nerve sheath membranes surrounding blood vessels that enter the spinal cord. Clinical manifestations Most intradural nerve sheath tumors have a long course; those in the thoracic segment have the shortest history, those in the cervical and lumbar segments have a longer one, and sometimes the duration of the disease can be more than 5 years. Tumors with cystic changes or hemorrhage have an acute course. The main clinical signs and symptoms of vertebral nerve sheath tumors are pain, sensory abnormalities, dyskinesia, and sphincter dysfunction. The incidence of sensory abnormalities is about 85%, and the incidence of pain is nearly 80%. The most common symptom is radicular pain, followed by sensory abnormalities and motor disorders. The pain of tumors in upper neck segment is mainly in the cervical neck, occasionally radiating to the shoulder and upper arm; the pain of tumors in cervicothoracic segment is mostly located in the back of the neck or upper back, and radiating to one or both sides of the shoulder, upper limb and chest; the tumors in upper thoracic segment often manifest as back pain radiating to the shoulder or chest; the pain of tumors in thoracic segment is mostly located in thoracic and lumbar region, and radiating to the abdomen, inguinal region and lower limbs. The pain of tumors in the thoracolumbar segment is located in the lumbar region and may radiate to the groin, arm, thigh and calf. The pain of lumbosacral segment tumor is located in the lumbosacral region, buttocks, perineum and lower limbs. Sensory abnormality as the first symptom accounts for 20%, which can be divided into two categories of sensory hypersensitivity and hyperalgesia. The former is characterized by ankylosis, numbness, coldness, acidity and burning; the latter is mostly the combined hyperalgesia of pain, temperature and touch. Sensory disturbances generally start from the distal end and gradually develop upward, the patient’s early subjective sensory abnormalities, while the examination of no special findings, followed by hyposensation, and finally the loss of all sensations along with motor function. The cones and cauda equina no longer have spinal cord parenchyma, so the sensory abnormalities are distributed in a peripheral nerve type, typically the anus and perineum skin show numbness in the saddle area. Movement disorder as the first symptom takes the 3rd place. Due to the different sites of the tumor, radicular or fascicular damage to the nerves can be produced, resulting in movement disorders. With the progression of symptoms, dysfunction of the pyramidal tract can occur, and thus the scope and degree of paralysis varies. Most patients come to the hospital with different degrees of mobility difficulties, and half of the patients have limb paralysis. The time of detection of dyskinesia varies depending on the tumor site, with cone or cauda equina tumors showing significant dyskinesia in advanced stages and thoracic tumors showing it earlier. Sphincter dysfunction is often a late symptom, indicating partial or complete compression of the spinal cord. The main clinical signs and symptoms of intraspinal nerve sheath tumors are pain, sensory abnormalities, movement disorders and sphincter dysfunction. 1, Spinal radiograph: direct sign is the calcified spot shadow of nerve sheath tumor, which is less common; indirect sign refers to the corresponding changes produced by the tumor compressing the vertebral canal and its adjacent bony structures, including the destruction of the vertebral arch, widening of the intervertebral root distance, or even the disappearance of the destruction of the vertebral arch root, the concavity of the vertebral body, or the enlargement of the intervertebral foramen, and so on. 2.Vertebral angiography: The rate of subarachnoid obstruction is more than 95%, and the typical one is cup-and-mouth filling defect. 3.CT and MRI examination CT scan is difficult to make a definite diagnosis. Tumor on MRI T1-weighted image shows extramedullary low-signal foci, and on T2-weighted image shows high-signal foci; enhancement scan: solid tumors show uniform enhancement, cystic tumors show ring-shaped enhancement, and a small number of tumors show non-uniform enhancement. Depending on the anatomical level where the tumor is located, there will be corresponding spinal cord displacement. 4, Lumbar puncture: The compression neck test shows different degree of subarachnoid obstruction; the cerebrospinal fluid circulation is impaired below the site of the tumor, and the tumor cells are detached, resulting in increased protein content of the cerebrospinal fluid. In addition, because the tumor is generally free in the spinal canal, the symptoms can be aggravated after lumbar puncture to release the cerebrospinal fluid, which is due to the change of the dynamics in the lumen of the spinal canal and the aggravation of the tumor compression on the spinal cord. Diagnosis If there is obvious radicular pain, motor and sensory deficits developing from the bottom up, an area of skin sensitivity at the level of the tumor segment, especially if there is spinal cord hemisection syndrome (manifested as motor paralysis of ipsilateral upper motor neurons and loss of tactile and deep sensation, and loss of contralateral sensation of pain and warmth below the diseased segment), and the pain is aggravated by the change of the cerebrospinal fluid dynamics, it suggests that the extramedullary neurinoma of the spinal cord may be possible, and the necessary auxiliary treatment is needed. Nerve sheath tumors of the extramedullary spinal cord may be diagnosed with the necessary ancillary investigations. Treatment Benign nerve sheath tumors are mainly treated by surgical resection, and the vast majority of cases can be cured by standard posterior laminectomy with total resection of the tumor, and recurrence is generally rare. Surgical resection of malignant nerve sheath tumors should be supplemented with radiation therapy. Prognosis Malignant nerve sheath tumors have an extremely poor prognosis, with survival rarely exceeding 1 year. These tumors must be differentiated from the few cases of Schwann cell tumors that exhibit aggressive histologic features, and those with a malignant tendency have a relatively good prognosis.