Spinal schwannoma epidemiology
Most intradural tumors are located within the intradural extramedullary compartment, and the most common tumors are spinal schwannomas and meningiomas. Other less common neoplasms include neurofibroma, solitary fibrous tumor,myxopapillary ependymoma, lymphoma, metastatic leptomeningeal disease, malignant peripheral nerve sheath tumor, and paraganglioma. 1).
Spinal schwannoma is most frequently seen in the cervical and lumbar regions, far more frequently than in the thoracic spine.
The incidence of spinal schwannoma is 0.3–0.5/100,000 individuals annually 2).
Its prevalence is similar in males and females, and it is usually diagnosed during the fourth and fifth decades of life 3).
Schwannomas have an incidence of 3% of all spinal tumors.
Most occur sporadically and are solitary, but they may also be associated with Neurofibromatosis type 2, but can occur with Neurofibromatosis type 1.
Spinal schwannoma constitutes approximately 25% of the intradural spinal tumors 4) 5) 6) 7) 8) 9) 10). 11) 12) 13) 14) 15).
Except in cases of neurofibromatosis, it is very rare for tumors of different pathological types to exist concurrently at the same spinal level, with only 9 cases reported to date, in which spinal meningioma was found with spinal schwannoma in 7 cases and with spinal neurofibroma in 2 cases 16).
Configuration
In a paraspinal location, they are the commonest cause of intradural extramedullary tumors but may also be extradural or extramedullary 17).
Most are entirely intradural, but 8-32 % may be completely extradural 18) 19). 1-19 % are a combination, 6-23 % are dumbbell spinal schwannomas, and 1 % are intramedullary schwannomas.
The most common location of spinal schwannomas are the lumbar spine (48%) 20).
Schwannomas are frequently located in the extramedullary region, and may present as dumbbell shaped in 10-15% of cases. They may also be located at the intramedullary region. Ten percent of the tumors were in the extradural location, and 1% in the intradural intramedullary regional location.
Up to 2.7% of schwannomas are located in the retroperitoneal region 21).
Most arise from the dorsal root of spinal nerve (sensory) rootlets (75%). Paraspinal schwannomas involve the dorsal nerve roots, affecting people in the fourth and fifth decades of life 22).