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Thoracolumbar intradural lesion
Introduction
Spinal tumors account for up to 15% of all tumors in the neuroaxis. Based on their anatomical location, the spinal tumors are classified as extradural, intradural extramedullary, or intradural intramedullary (spinal cord tumors). Intradural tumors account for 3% of primary central nervous system (CNS) tumors, and the most common histological types are meningiomas and nerve sheath tumors (NSTs). Microsurgical resection plays an essential role since the large majority of primary spinal intradural tumors are benign and encapsulated and a complete surgical resection is curative. In this chapter, we utilize an example case to illustrate the key clinical and radiographic features as well as the surgical management of intradural extramedullary tumors in the thoracolumbar region.
Example case
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Chief Complaint : leg pain
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History of present illness : A 55-year-old female with a 6-week history of pain in her legs when walking and/or standing and increased urinary frequency. She denies any weakness. She underwent imaging which was concerning for an intradural extramedullary spinal cord tumor ( Fig. 53.1 ).
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Medications : none
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Allergies : no known drug allergies
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Past medical history : none
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Past surgical history : none
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Family history : none
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Social history : none
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Physical examination : awake, alert, and oriented to person, place, and time; cranial nerves II–XII intact; motor and sensory intact
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Laboratories : complete blood count (CBC) and basic metabolic panel (BMP) within normal limits
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Lumbar spine MRI : intradural extramedullary T2 hyperintense lesion with heterogeneous gadolinium enhancement at the T11–12 level displacing the conus medullaris to the left
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| Preoperative | ||||
| Additional tests requested |
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Neurophysiological evaluation (MEP, SSEP, EMG) | CT thoracic spine |
| Surgical approach selected | T11–12 laminectomy with resection of tumor | T11–12 right hemilaminectomy and excision of tumor | T11–12 right hemilaminectomy and excision of tumor | T11–12 laminectomy, resection of tumor, T12 laminoplasty |
| Goal of surgery | Diagnosis, gross total resection of tumor | Diagnosis, gross total resection, decompression of conus | Gross total resection, preservation of neurological function | Gross total resection, prevent progression of neurological symptoms |
| Perioperative | ||||
| Positioning | Prone in pins | Prone | Prone | Prone on Jackson table, no pins |
| Surgical equipment |
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| Medications | Steroids | MAP >80 | Steroids, maintain MAP | None |
| Anatomical considerations | Conus medullaris | Spinal cord, vasculature | Cauda equina, conus | Spinal cord, posterior spinal artery |
| Complications feared with approach chosen | CSF leak, spinal cord injury | CSF leak, spinal cord injury | CSF leak, spinal cord injury | CSF leak, spinal cord injury, vascular injury |
| Intraoperative | ||||
| Anesthesia | General | General | General | General |
| Exposure | T11–12 | T11–12 | T11–12 | T11-T12 |
| Levels decompressed | T11–12 | T11–12 | T11–12 | T11–12 |
| Levels fused | None | None | None | T12 |
| Surgical narrative | Position prone in pins, IOM, fluoroscopy to confirm levels based on rib count, incision, subperiosteal dissection of paraspinal muscles from spinous process and laminae to identify pars interarticularis and medial joint, fluoroscopy to confirm levels, match stick used to resect through base of spinous process and cerebellar retractor used to displace interspinous ligament to the left, complete partial laminectomies at T11 and T12 with dill and Kerrison punch, ultrasound to confirm extent of laminectomies and exposure of tumor, operative microscope brought into view, | Position prone on gel rolls, plan incision used AP and lateral x-rays to localize level with AP counting from last rib and lateral x-rays from L5 to S1, midline skin incision and subperiosteal muscle dissection on right side, place self-retaining William’s retractors, confirm level with x-ray, right T11–12 laminectomy across midline and partial facetectomy using drill and Kerrison rongeurs, confirm exposure with ultrasound, open dura preserving arachnoid under microscopic visualization, dural stay sutures, open arachnoid around mass with scissors, control proximal | Position prone, identify T12 with K-wire and x-ray, 5–6 cm midline skin incision, muscular dissection only on right side, right T11–12 hemilaminectomy with drill and Kerrison rongeur under microscope, undercut base of spinous process for more midline exposure, midline dural opening, identify tumor and check relationship with conus/nerve roots/filum, dissect arachnoid from tumor and nerve roots, continuous IOM | Position prone, plan incision using intraoperative x-ray, midline incision from T11 to 12, subperiosteal dissection, x-ray to confirm levels, ultrasonic bone scalpel to perform T11-T12 laminectomy, ultrasound to confirm exposure, dura opened over tumor and tacked back, surgical microscope brought in and arachnoid incised and held to dura using vascular clips, IOM to identify and dissect motor and sensory branches |
| dura opened and tacked back, arachnoid opened sharply, stimulate dorsal aspect of tumor with positive control and sequential reduction to 0.1 mA, capsule cauterized and opened sharply, intralesional debulking with ultrasonic aspirator, manipulate capsule to identify fascicles giving rise to tumors, fascicles stimulated with nerve stimulator and cut if no motor response, dural closure with running nonlocking suture, drain placed in epidural space | CSF flow with Gelfoam and cottonoids, bipolar surface vessels, send specimen to pathology, internally debulk tumor with ultrasonic aspirator, dissect mass circumferentially with extra attention to medial dissection from spinal cord, identify nerve root from which mass is originating, stimulate to confirm absence of function, cut nerve proximally and distal to mass, dissect mass from dura if meningioma, watertight dural and fascial closure, layered closure, flat in bed for 12–24 hours | and change surgical strategy if change in signals, en bloc resection, watertight dural closure with autologous fat and fibrin glue, layered closure | with goal of preserving motor branches, lesion completely resected, dura closed in watertight fashion and multiple Valsalva maneuvers performed, fibrin sealant patch over dural closure, T12 replaced with titanium plates, layered closure, bedrest overnight | |
| Complication avoidance | Preserve interspinous ligament, nerve stimulator, intralesional debulking to identify fascicles giving rise to tumor | AP and lateral x-rays for identifying surgical level, right hemilaminectomy, ultrasound to confirm exposure, extra attention when dissecting from spinal cord, stimulate nerve to confirm nonfunctioning before removing | Right hemilaminectomy, undercut spinous process for more medial exposure, continuous IOM and change surgical strategy if chance in signals, en bloc resection, autologous fat for closure | T12 laminoplasty, ultrasound to confirm exposure, ION to determine whether sensory or motor nerve roots involved, Valsalva to test dura closure |
| Postoperative | ||||
| Admission | ICU | Floor | Floor | Floor |
| Postoperative complications feared | CSF leak | CSF leak, neurological deficit, residual tumor | CSF leak, neurological deficit | CSF leak, new neurological deficit |
| Anticipated length of stay | 2–3 days | 2 days | 5–7 days | 2 days |
| Follow-up testing | MRI T-L spine within 72 hours of surgery | MRI T-spine within 24 hours of surgery | MRI T-spine 3 months after surgery | MRI T-spine within 72 hours, then 3 months, 6 months, and annually after surgery |
| Bracing | None | None | None | None |
| Follow-up visits | 3 weeks after surgery | 2 weeks, 6 weeks, 3 months after surgery | 2 weeks, 3 months after surgery | 3 weeks after surgery |
AP , Anteroposterior; CSF , cerebrospinal fluid; CT , computed tomography; EMG , electromyography; ICU , intensive care unit; IOM , intraoperative monitoring; MAP , mean arterial pressure; MEP , motor evoked potential; MRI , magnetic resonance imaging; SSEP , somatosensory evoked potential.
Differential diagnosis
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Schwannoma
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Meningioma
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Myxopapillary ependymoma
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Metastasis
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Solitary fibrous tumor
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Neuroendocrine tumor or paraganglioma
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