In a paraspinal location, they are the commonest cause of intradural extramedullary tumors but may also be extradural or extramedullary 13).
Most are entirely intradural, but 8-32 % may be completely extradural 14) 15). 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%) 16).
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 17).
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 18).
The final diagnosis should be established by clinical findings and imaging methods and MRI is the best method for diagnosis and differential diagnosis.
The size and specific margins of the mass demonstrate the localization and invasion to the contiguous structures. The changes such as foramen enlargement and erosion in the pedicles detected in the direct graphs may be seen as masses with sharp margins and involve the peripheral contrast in the CT scans.
Paraspinal schwannomas are frequently asymptomatic and diagnosed incidentally on imaging of the spine 19).
Surgical resection is the treatment of choice 20) 21).
They need a tailored treatment, which in most cases works through one surgical approach. Usually it is possible to perform a complete resection with a good postoperative prognosis 22).
Unlike neurofibromas, schwannomas do not arise from the nerve fibers and so the tumor is easily separated from nerve fibers without neurologic compromise. In the rare case that this is impossible, the remnant tumor may be followed up radiographically if it is histologically benign. Malignant schwannomas are treated with adjuvant radiation therapy.
In the series of Asazuma et al., a posterior approach was used in 35 patients; 7 others underwent a combined anterior and posterior approach. A posterior approach was used for all type IIa and IIIa tumors, and for some type IIIb (upper cervical), IV, and VI tumors; a combined posterior and anterior approach was used for type IIb and the remainder of type IV and VI. Reconstruction was performed using spinal instrumentation in 4 patients (9.5%). Resection was subtotal in 6 patients (14.3%) and total in 36 (85.7%). 23).
Recurrence is rare after total excision (except in neurofibromatosis).
The risk for motor deficit is higher for schwannomas than for neurofibromas, for cervical vs. lumbar tumors, and for cervical tumors wiyh extradural extension.
The subjects were 48 patients (22 males and 26 females) with spinal schwannoma who were classified into three subgroups: iso/homo, high/rim, and hetero/hetero, based on T2WI/contrast T1WI. A retrospective analysis of tumor size and MIB-1 index was performed in the context of these MRI findings. Intraoperative findings and pre- and postoperative motor performance were also examined.
The average tumor size was 32.4 mm (range 10-130 mm) and the average MIB-1 index was 3.8% (range 1-12). In the three subgroups, there were no significant differences in sex, age, duration of disease, tumor lesion, and dumbbell type. In the hetero/hetero group, the tumor size was significantly greater and the MIB-1 index was significantly higher (both P < 0.05), than the other two groups. The tumor adherence rate was significantly higher for hetero tumors (P < 0.05) and preoperative paralysis was more common in cases with tumor adhesion. The rate of paralysis improvement at 1 month was significantly lower for hetero tumors, but all cases had improved at 6 months.
Contrast T1WI MRI was useful for prediction of the proliferative activity and growth of spinal schwannomas, which are associated with increased tumor size and adhesion. A heterogeneous pattern on contrast T1WI indicated an increase in size and adhesion of the tumor. This pattern reflected the preoperative motor status and postoperative motor recovery 24).
Thirty-two patients with giant spinal schwannomas underwent surgery between September 1998 and May 2013. Tumor size ranged from 2.5 cm to 14.6 cm with a median size of 5.8 cm. There were 9 females (28.1%) and 23 males (71.9%), and the median age was 47 years (range 23-83 years). The median follow-up duration was 36.0 months (range 12.2-132.4 months). Three patients (9.4%) experienced recurrence and required further treatment. All recurrences developed following subtotal resection (STR) of cellular or melanotic schwannoma. There were 3 melanotic (9.4%) and 6 cellular (18.8%) schwannomas included in this study. Among these histological variants, a 33.3% recurrence rate was noted. In 1 case of melanotic schwannoma, malignant transformation occurred. No recurrence occurred following gross-total resection (GTR) or when a fibrous capsule remained due to its adherence to functional nerve roots.
Resection is the treatment of choice for symptomatic or growing giant schwannomas, frequently requiring anterior or combined approaches, with the goals of symptom relief and prevention of recurrence. In this series, tumors that underwent GTR, or where only capsule remained, did not recur. Only melanotic and cellular schwannomas that underwent STR recurred 25).
Consecutive 49 patients with intradural extramedullary (IDEM) schwannoma were surgically resected: 31 patients via MIS approach (MIS group), 6 patients via muscle-splitting using tubular retractor, and 25 patients via unilateral hemilaminectomy preserving the contralateral paraspinal muscle. Eighteen patients underwent total laminectomy (TL group). Medical record including perioperative data and radiologic data were reviewed.
On initial magnetic resonance image, mean maximal sagittal diameter of tumor was 23.9 mm and 26.9 mm, and mean maximal axial diameter was 16.1 mm and 22.8 mm in MIS and TL group, respectively (p=0.452 and p=0.011, respectively). The foraminal extension of tumor was identified in 8 in MIS and 9 in TL group (p=0.081). The tumor location involved was mostly observed in 20 lumbar spines in MIS group and 17 cervicothoracic spines in TL group (p=0.001). Intraoperatively, all tumors in MIS group could be totally resected with reduced operative time and blood loss. During the follow-up period of 38.2 months and 51.2 months in the MIS and TL group, the clinical improvement was not different between the surgical approaches (p=0.332).
Safe and complete resection of IDEM schwannoma was obtained through MIS approach. Regardless of sagittal extension of tumor, axial diameter within 16 mm-sized schwannoma located at the lumbar spine could be an effective indication for MIS approach even for foraminal extension 26).
Conti et al., present a series of 179 spinal neurinomas consecutively observed at the Department of Neurosurgery at the University of Florence for a period of 30 years (between 1967 and 1997). We decided to limit the retrospective study to obtain at least 5 years of follow-up. Therefore, 20 additional neurinomas treated between 1997 and 2002 were excluded.
All the cases are evaluated under statistical, clinical, neuroradiological, and surgically technical profiles based on data from clinical records and from periodic check-ups after surgery. In particular, the results are analyzed on the basis of an accurate pre- and postsurgical evaluation using Karnofsky’s scale and Kleklamp-Samii’s scoring system.
We treated 179 spinal neurinomas in 152 (93 male and 59 female) patients. The mean age was 44.3. In 33 cases the neurinoma was sited in the cervical tract, in 59 cases in the dorsal tract, and in 87 cases in the lumbo-sacral tract. Eleven patients harbored Recklinghausen’s neurofibromatosis (7 NF1 and 4 NF2 of which 1 was intramedullary). In 123 cases the neurinoma was intradural, in 11 cases it was extradural, in 2 intra/extradural, in 9 it had a dumbbell form, and in 2 cases it was intramedullary; the remaining cases had neurofibromatosis. The most common presurgical symptom was segmental pain. Total removal of the lesion was possible in the first operation for 174 neurinomas. We encountered 3 cases of malignant neurinoma of which 1 was in NF2. The result of surgery was recovery in 108 cases; 2 patients with NF2 died, and local recurrence occurred even after total exeresis (excision) and radiotherapy in the cases of malignant neurinoma.
Schwannomas represent the most frequent tumor lesions of the spine with prevalence for the cervical-inferior tract and the dorso-lumbar passage. Intramedullary neurinomas are rarely observed. The total surgical removal of neurinomas is often an attainable goal, and clinical improvement is the common outcome with exception to malignant forms and NF2 neurofibromatosis. We describe a series of 179 treated schwannomas 27).
Are spinal schwannomas as benign as we think? To what extent do patients recover? Are patients prone to develop late complications such as cystic myelopathy or symptomatic spinal deformity? Is their life expectancy compromised? In an effort to answer these questions, the authors analyzed the long-term outcome for 187 patients from one neurosurgical department with surgically treated spinal schwannoma. Median follow-up period was 12.9 years (2454 patient years). One-fifth of the patients considered themselves free of symptoms at follow-up examination. The most common late complaint was local pain (46%), followed by radiating pain (43%), paraparesis (31%), radicular deficit (28%), sensory deficit due to a spinal cord lesion (27%), and difficulty voiding (19%). Late complications occurred in 21% of the patient population, including cystic myelopathy (2%), spinal arachnoiditis (6%), spinal deformity (6%), and troublesome pain (7%). Life expectancy of the patients corresponded to that of the general population 28).