Functional Outcomes following Surgical Management of Intradural Extramedullary Spinal Cord Tumors

Background Data: Intradural extramedullary tumors are mostly benign lesions that often present late due to their slow rate of growth. Recent advances in the field of neuro-imaging have greatly increased the ability to identify these tumors in early stages. The most effective treatment modality for these tumors is gross total resection, which can sometimes be associated with neurological morbidity and functional impairment. Purpose: to evaluate the functional outcomes following surgical excision of intradural extramedullary spinal tumors. Study Design: This is a retrospective cohort clinical case study. Patients and Methods: In this study the medical records of patients who underwent surgery for intradural extramedullary tumors at Ain Shams University Hospitals and Banha University Hospital between 2012 and 2015 were reviewed. Patient’s demographics, clinical presentation, radiographic findings, tumor location, histopathological findings and neurological outcome were documented from patients’ files. Pain was evaluated by Visual Analog Scale and neurological function was graded before and after surgery by Nurick’s Functional Grading System. Results: This study included sixteen patients with intradural extramedullary mass lesions. Six were males (37%) and 10 were females (63%), mean age at presentation was 41 years (range 24 to 63 years). Histopathologically, there were 10 schwannomas (62%), 4 meningioma (%25) and 2 Neurofibromas (%13). Based on the location, we had 9 thoracic, 3 cervical and 3 lumbar lesions. There was improvement of the mean VAS score from 7.8 preoperative


Introduction
Spinal cord tumors represent 10% of central nervous system tumors.Intramedullary location represents the largest percentage in children while intradural extramedullary tumors represent around 60% in adults and most commonly reported in the dorsal region more than cervical and lumbar regions.Histopathologically, most of those tumors are nerve sheath tumors and meningiomas. 3,4,5erve sheath tumors arise from supporting cells adjacent to neurons within spinal nerve roots and they represent around 50% of intradural extramedullary lesions.They are either categorized as schowannomas which accounts for 85% or neurofibromas accounting for the remaining 15%. 15Meningiomas are the second most common intradural extramedullary tumors, representing 40%.They arise from arachnoid cap cells and are seen four to nine times more frequently in women than in men. 9 Intradural extramedullary tumors are typically slow growing lesions that may be asymptomatic for many years before presentations.The presenting symptoms are usually influenced by tumor's spinal level and size.Both cervical and thoracic tumors can enlarge and compress the cord resulting in myelopathy.Cervical tumors are more likely to present with neck pain, brachialgia and hand weakness.Thoracic tumors often present with back pain, myelopathy and sensory disturbances in lower half of the body.Tumors of the cauda equina usually may cause back pain, sciatica, weakness in lower limbs and sphincters disturbances. 10,12adolinium-enhanced MRI greatly increase the ability to identify the tumors in early stage and its relation to the spinal cord.The most effective treatment of intradural extramedullary tumors is total excision. 16

Patients and Methods
This is a retrospective cohort clinical case study, conducted on 16 patients with intradural extramedullary spinal cord tumors, operated upon at Ain Shams University Hospitals and Banha University Hospital, between 2012 and 2015.Patients' demographics, clinical presentation, radiographic findings, tumor location, histopathological findings and neurological outcome were documented from patients' files.Pain was evaluated by visual analog scale (VAS) and neurological function was graded before and after surgery according to Nurick's Functional Grading System. 13The mean follow up period was 6 month ranging from 3 to 14 months.Surgical Technique: Systemic antibiotics were administered one hour before surgery.Under general anesthesia the patient was placed in prone position.Tumor's spinal level was marked with the aid of intraoperative C-arm.Sterilization and draping was done.A posterior midline skin incision was made and fascia was divided and the para-spinal muscles were stripped exposing the lamina.Laminectomy was performed in 14 cases, while in the remaining 2 cases hemilaminectomy was sufficient.Bone waxing and homeostasis was done prior to durotomy to maintain a clear intradural operative field.Operating microscope was used for opening the dura and tumor resection.The dura was tented over a cottonoid lining the epidural space at the limit of laminectomy and secured to the paravertebral muscles.Tumor was dissected from surrounding neuronal elements and removed enbloc if possible (Figure 1), while piecemeal tumor removal was used in large tumors.The remaining part of the tumor was inspected properly to identify its origin from the nerve root.If the tumor was found to be attached to the dura, the dural attachment was coagulated using bipolar coagulation.After removal of tumor, hemostasis was achieved and the dura was sutured with Proline 4-0 in a water tight fashion.Dural graft was used in one case of meningioma.Sub-fascial drain was inserted and the wound was closed anatomically in layers.

Patient Demographics:
This study included sixteen patients with intradural extramedullary tumors, 6 were males (37%) and 10 were females (63%).Mean age at presentation was 41 years (Range 24 to 63 years).Histopathologically, there were 10 schwannomas (62%), 4 meningioma (%25) and 2 neurofibromas (%13).Based on the anatomic location, there were 9 thoracic, 3 cervical and 3 lumbar lesions.The most common presenting symptom was pain which was observed in all patients, motor weakness was present in 11 patients while sphincter disturbance was reported in 4 patients.Ten patients were ambulant, 4 were ambulant with help and 2 patients were wheel chair bound.The mean preoperative VAS was 7.8 and the mean preoperative Nurick's grade was 3.1.

Patient Outcomes:
The mean VAS score was reduced from 7.8 preoperatively to 1.6 three month postoperatively (Figure 2).Preoperatively, according to Nurick's grading system there were two cases classified as grade 1, three cases as grade 2, five cases as grade 3 and four cases as grade 4 and two cases as grade 5.At three months after surgery ten cases were Nurick's grade 1, two cases were grade 2, three cases were grade 3 and one case was grade 4 (Table 1, Figure 3).Total resection (Figure 4) was achieved in 14 cases (87%).In the remaining 2 cases (13%), subtotal resection was achieved.The reason for subtotal resection was anterolateral tumor location in a case with meningioma and an intervertebral foramen extension in a case with schwannoma.These 2 patients are being followed up by regular clinical examination and Magnetic Resonance Imaging every 6 months in the first year and annually afterwards.Postoperative complications were experienced in 2 patients (13%), one of them had cerebrospinal fluid leak which required insertion of a lumbar drain and the other one had wound infection that was treated by antibiotics and debridement.None of our patients experienced any new neurological deficit.There was no tumor recurrence during the period of follow up.

Discussion
The development of spinal cord tumor surgery began in 1887 when Dr. Horsley removed an intradural extramedullary tumor located at dorsal spine in male patient who presented with spasticity and paraplegia. 7After surgery the patient made remarkable recovery and regained the ability to walk.Since then, surgery for spinal cord tumor has evolved through the advent of new techniques such as microsurgery, neuroimaging and intraoperative monitoring.As most of intradural extramedullary tumors are benign, well circumscribed and show clear

A B
demarcations to spinal cord tissue, surgery offers good chance for total excision of the tumor.Early diagnosis and early management of spinal tumors remain the most crucial elements affecting the outcome of such tumors. 2revedello et al, 14 studied 44 patients with intradural extramedullary tumors, their mean age was 32.9 years, most of tumors were located at the thoracic spine (45.5%),Schwannoma was the most common` tumor (65.9%) followed by meningioma (20.5%).Similarly in our series, most of our patients were in 3 rd and 4 th decade of their life, thoracic spine was the commonest location and Schwannomas were the commonest type of tumor encountered.Song et al, 17 reported in their series that the most common presenting symptoms were pain in 83.3% of patients followed by motor weakness in 50%, sensory disturbance in 41.6% and sphincter disturbance in 33.3%.In our study, the most common presenting symptoms were pain in 100% of patients.The second most common symptoms were motor weakness 68% followed by sphincter disturbance in 25%.
Many studies of intradural extramedullary tumors reported marked improvement of pain after surgery.Ahn et al, 1 revealed that the mean VAS score was reduced in all cases from 8 before surgery to 1.2 after surgery, whereas Ahsan et al, 2 reported a reduction of the mean VAS score from 7.67 preoperatively to 1.14 postoperatively.Consistent with previous studies, in our series the mean VAS score was reduced from 7.8 preoperative to 1.6 postoperative.
Although each study of intradural extramedullary tumors used different scale as a measuring tool to assess the pre and postoperative neurological status, all of them reported significant neurological improvement after surgery.Konovalov et al, 11 reported that 50% of patients moved to higher functional class of McCormick scale after laminectomy and resection of tumor.Similarly, Gu et al, 6 revealed that 93% of their patients had improved frankel grade, whereas 7% of patients had no change in their grade after surgery.Ahsan et al, 2 and Ahn et al 1 reported that the mean Nurick's grade has improved from 3 preoperatively to one postoperatively.Consistent with previous studies, in our series there was improvement of the mean Nurick's grade from 3.1 preoperatively to 1.6 postoperatively.
The goal of treatment of intradural extramedullary tumors is maximal tumor removal without neurological injury.In this series, total resection was achieved in 87.5% of cases and subtotal resection in 12.5% of cases.Similar outcomes were observed by kim et al, 8 who reported complete resection of tumor in 94% of cases and Turel et al, 18 who achieved total removal in 93% of cases in their series.

Conclusion
Intradural extramedullary tumors are mostly benign and slowly growing lesions that may be asymptomatic for many years before presentation.These tumors can be resected through a standard posterior approach.Favorable outcomes can be achieved by early diagnosis and total resection of the tumor.

Figure 2 .
Figure 2. Preoperative and postoperative Mean VAS score and mean Nurick's Functional Grade

Table 1 .
Study population and outcomes.