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Intradural extramedullary tumor
Introduction
Intradural extramedullary (IDEM) tumors arise within the confines of the dura mater but are not intrinsic to the spinal cord itself. Epidemiological studies have reported an incidence of approximately 0.74 per 100,000 person years. These tumors are typically considered benign, with the most common being meningiomas, followed by nerve sheath tumors. Despite being benign, IDEM tumors can lead to significant morbidity secondary to direct compression of the spinal cord, also leading to debilitating weakness. These tumors may be seen in conjunction with syndromes such as neurofibromatosis and schwannomatosis, which will likely alter the management strategy, as these patients tend to be younger in age with multiple tumors growing at different rates. The most common presentation for these tumors is pain, which may be radicular or axial back pain, and since these tumors grow slowly over time, they may present with progressively worsening myelopathy from spinal cord compression. It is rare for these tumors to present with spinal instability, and when instability is present, one should include more aggressive tumors in the differential diagnosis. In this chapter, we will discuss the management and surgical tenets for a patient with a large ventral IDEM tumor.
Example case
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Chief complaint : weakness
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History of present illness : This is a 69-year-old male with a history of weight loss as well as atrophy of his upper extremity. In addition, he has had difficulty with ambulation and increasing loss of dexterity over the past couple of weeks. This has progressively worsened, and he has significantly deteriorated over this period of time. He underwent imaging concerning for a spinal cord tumor ( Fig. 47.1 ).
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Medications : tamsulosin
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Allergies : no known drug allergies
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Past medical history : weight loss, prostate cancer status post radiation
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Past surgical history : none
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Family history : noncontributory
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Social history : nonsmoker
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Physical examination : awake, alert, and oriented x 3; cranial nerves CNII–XII intact
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Motor: right: deltoids/triceps/biceps/interossei 3/5; left: deltoids/triceps/biceps/interossei 4/5; bilateral iliopsoas/knee flexion/knee extension/dorsi, and plantar flexion 4/5
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Reflexes : 2+ in bilateral biceps/triceps/brachioradialis with negative Hoffman; 2+ in bilateral patella/ankle; no clonus or Babinski; sensation intact to light touch
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Laboratories : basic metabolic panel, heme-8, coagulation all within normal limits
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| Preoperative | ||||
| Additional tests requested |
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| Surgical approach selected | C5-T1 laminectomy and resection of tumor with C5-T1 posterior fusion | C5-C7 laminectomy and resection of tumor with possible C5-C7 posterior fusion | C5-T1 laminectomy and resection of tumor with C4-T2 posterior fusion | |
| Goal of surgery | Spinal cord decompression | Spinal cord decompression, gross total resection | Diagnosis, spinal cord decompression, tumor removal, spinal fusion | Diagnosis, spinal cord decompression, tumor removal, spinal fusion |
| Perioperative | ||||
| Positioning | Prone with Mayfield pins | Prone with Mayfield pins | Prone on Jackson table with Mayfield pins | Prone with Mayfield pins |
| Surgical equipment |
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| Medications | Steroids | Steroids, mannitol, MAP >80 | Steroids, MAP 85 | Steroids, MAP >85 |
| Anatomical considerations | Spinal cord, right C6, C7-C8 motor nerve roots | Spinal cord, nerve roots, vertebral artery, right-side facet joint | Spinal cord, C6 and C7 nerve roots, vertebral arteries | Spinal cord, right C6, C7-C8 motor nerve roots, dentate ligaments |
| Complications feared with approach chosen | Progressive neurological decline | Instability, spinal cord/nerve root injury, vertebral artery injury, dysphagia | Nerve root injury | New weakness, pseudomeningocele, spinal cord infarct |
| Intraoperative | ||||
| Anesthesia | General | General | General | General |
| Exposure | C5-T1 | C5-T1 | C4-T2 | C4-T1 |
| Levels decompressed | C5-T1 | C5-C7 | C5-T1 | C5-7 |
| Levels fused | C5-T1 | C5-C7 if needed | C4-T2 | C4-T1 |
| Surgical narrative | Position prone, IOM, fluoroscopy to confirm levels, placement of C5-7 lateral mass and T1 pedicle screws, delay right rod placement until end of case, spinous process resection C5-7 and partial T1 with Leksell rongeur, laminectomy with 3 mm matchstick, resect ligamentum flavum with a #15 blade, ultrasound to confirm laminectomy sufficient, operating microscope brought in, dura opened and tacked back, arachnoid opened sharply, identify tumor/spinal cord interface, nerve stimulator on posterior capsule of tumor, sharp opening in pia with #11 blade, intralesional debulking with ultrasonic aspirator, frozen section for diagnosis, sequential debulking of tumor away from spinal cord, fascicles giving rise to the tumor are sacrificed, great care to preserve functional motor nerve fascicles at 0.1 mA, dural closure with running nonlocking suture, thrombin glue and Gelfoam are placed over durotomy, drain placed in epidural space, suction for 24 hours and then straight drainage | Position prone, midline incision exposing spinous process of C5-T1, midline laminectomy removing spinous processes and lamina C5-C7, undercut facet joint and expose involved foramen on right side, identify tumor in the foramen and fully expose medial dura, right-side T-shaped with limb extending laterally to involved nerve root, tack dura, arachnoid opened and tacked with clips, expose tumor along its length, dissect tumor away from cord medial to lateral and develop plane along its length, debulk with ultrasonic aspirator to allow tumor retraction away from cord toward foramen, lateral tumor may be delivered medially after sufficient debulking, attempt to preserve nerve as long as nonfunctional, care is taken to identify vertebral artery laterally with use of Doppler if needed, water-tight dural closure with patch if necessary, if risk of instability consider fusion from C5-7 with lateral mass screws and bone graft, layered closure | Position prone, expose C4-T2, predrill screw holes from C4 to T2 except C6-7 on the right with surgical navigation. C5-T1 laminectomy, intraoperative ultrasound to confirm tumor location, right lateral bony resection to reach extraforaminal component of the tumor, remove inferior facet of C6 and superior facet of C7, follow C7 nerve root laterally, midline durotomy under microscope, tack up dura, coagulate tumor capsule, intralesional tumor debulking with ultrasonic aspirator, frozen section, find arachnoid plane within spinal cord, debulk more tumor if necessary to decrease spinal cord manipulation, find rootlet origin of tumor and stimulate if necessary, remove if no stimulation, remove tumor laterally while constant nerve stimulation, water tight dural closure with onlay and glue if necessary, screws from C4 to T2, decorticate bone, layered closure with water tight facial closure | Position prone, Trendelenburg position, x-ray to plan incision from C4 to T1, midline incision, subperiosteal dissection, intraoperative x-ray to confirm levels, place lateral mass holes at C4 bilaterally/left C5-6 using Magrel technique, place T1 pedicle screws bilaterally, en bloc laminectomy from C5 to 7, intraoperative ultrasound to assess exposure, midline dura opening and dura tacked up with arachnoid, plane is created medially between tumor and spinal cord bluntly and extended cranially and caudally, dentate ligaments identified and sectioned after stimulating, tumor mobilized form medial to lateral to identify neural structures entering tumor and stimulated, internally debulk tumor after confirming lack of stimulation using ultrasonic aspirator to fold in tumor and identify en passage nerve roots, potential facetectomy to identify right nerve roots if needed, dural closure with GoreTex suture and fibrin glue, Valsalva to assess for leakage, place lateral mass screws at C4-6 bilaterally, secure rods, x-ray to assess instrumentation, final tighten, layered closure |
| Complication avoidance | Instrumentation prior to decompression, avoid Kerrison punches to avoid neurological injury, ultrasound, nerve stimulation to guide resection | Extend exposure on right side to identify foramen, right-side T-shaped with limb extending laterally to involved nerve root, expose tumor along its length and dissect from medial to lateral away from cord, debulk tumor to allow mobilization, identify vertebral artery | Lateral cord exposure, debulk tumor to minimize spinal cord manipulation, nerve stimulation to guide resection | Trendelenburg position to help with venous drainage, Magerl technique for lateral mass screws, en bloc laminectomy, intraoperative ultrasound to assess exposure, section dentate ligaments to mobilize spinal cord, stimulate structures to identify neural structures |
| Postoperative | ||||
| Admission | ICU | ICU | Floor | Floor |
| Postoperative complications feared | Progressive myelopathy or functional radiculopathy | CSF leak, spinal instability, infection | New weakness from cord or root injury, CSF leak | New weakness, pseudomeningocele, spinal cord infarct |
| Anticipated length of stay | 4 days | 5–7 days | 3–5 days | 2–3 days |
| Follow-up testing | MRI 72 hours after surgery, prone with Mayfield pins | MRI C-spine prior to discharge |
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MRI C-spine 3 months after surgeryCT C-spine 6 months after surgery |
| Bracing | None | None | None | None |
| Follow-up visits | 3 weeks after surgery | 2 weeks, 6 weeks, 6 months, 1 year after surgery | 2 months after surgery | 2 weeks, 6 weeks, 6 months, 1 year after surgery |
CT , Computed tomography; CTA , computed tomography angiography; EMG , electromyography; ENT , ear, nose, and throat; ICU , intensive care unit; IOM , intraoperative monitoring; MAP , mean arterial pressure; MEP , motor evoked potential; MRI , magnetic resonance imaging; PSA , prostate specific antigen; SSEP , somatosensory evoked potential.
Differential diagnosis
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Schwannoma
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Meningioma
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Metastasis
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