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Intradural extramedullary (IDEM) tumors are tumors of the neuro-axis that grow within the confines of the dura mater but are extrinsic to the spinal cord itself. Epidemiological studies have estimated the incidence of IDEM tumors to be approximately 0.74 per 100,000 persons. Although a variety of tumor types may be found within this compartment, the most common are benign tumors such as meningiomas or schwannomas. Meningiomas are benign tumors arising from arachnoid cap cells of the dura; thus, they are typically attached to the dura with a broad base. Their histology is identical to their intracranial counterpart. Schwannomas arise from the dorsal or ventral nerve root, with the dorsal roots being more common. These tumors are hypothesized to originate in the Obersteiner-Redlich zone, which is the transition point between oligodendrocytes of the central nervous system and Schwann cells of the peripheral nervous system. Schwannomas typically arise from a single-nerve fascicle and displace the surrounding roots, causing compression and leading to pain, sensory loss, and weakness. Although these tumors arise from the nerve fascicle itself, this involved fascicle rarely contains functional tissue and thus can typically be ligated without clinical sequelae.
The most common tumors to be found in the sacrum are metastases or a primary tumor such as chordoma, but other tumor types can also be found originating in the sacral region. Schwannomas of the sacrum are rare and account for approximately 1% to 5% of all spinal schwannomas. There have been limited reports discussing the surgical management of these cases. In this chapter, we discuss the management of a patient with a sacral tumor and discuss the anatomical associations to be considered when approaching this region.
Chief complaint: urinary retention, buttock pain
History of present illness: This is a 43-year-old female with right-sided buttock pain and urinary retention for 1 year. She has no pain in her legs. She reports subjective decrease in sensation in her genitals. Magnetic resonance imaging (MRI) of the sacrum raises concern for a nerve sheath tumor ( Fig. 50.1 ).
Medications: gabapentin, antidepressants
Allergies: no known drug allergies
Past medical history: none
Past surgical history: hysterectomy, C-section
Family history: no history of malignancies
Social history: none
Physical examination: awake, alert, and oriented to person, place, and time; cranial nerves II–XII intact; bilateral deltoids/triceps/biceps 5/5; interossei 5/5; iliopsoas/knee flexion/knee extension/dorsi, and plantar flexion 5/5
Reflexes: 2+ in bilateral biceps/triceps/brachioradialis with negative Hoffman; 2+ in bilateral patella/ankle and no clonus or Babinski; sensation intact to light touch
Laboratories: all within normal limits
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Preoperative | ||||
Additional tests requested | None |
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Urodynamic testing |
Surgical approach selected | S1-2 laminectomy for resection of tumor | S1-2 laminectomy for resection of tumor | S2 laminectomy for resection of tumor | S2-4 laminectomy for resection of tumor |
Goal of surgery | Diagnosis, decompression of nerve roots | Diagnosis, gross total resection | Diagnosis, maximal safe resection, prevent further deterioration | Decompression of nerve roots, resection of lesion |
Perioperative | ||||
Positioning | Prone | Prone | Pone | Prone |
Surgical equipment |
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Medications | None | Ketorolac 48 hours after surgery | +/– steroids | None |
Anatomical considerations | Sacral nerve roots namely sciatic and pudendal |
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Sacral nerve roots, dura | S2-S4 sacral nerve roots |
Complications feared with approach chosen | Nerve root injury, CSF leak | S2 nerve root injury, CSF leak | Residual lesion, CSF leak, nerve root injury causing urinary incontinence | Nerve root injury |
Intraoperative | ||||
Anesthesia | General | General | General | General |
Exposure | S1-3 | S1-2 | S2 | S2-4 |
Levels decompressed | S1-2 | S1-2 | S2 | S2-4 |
Levels fused | None | None | None | None |
Surgical narrative | Position prone, medial incision from S1-3, subperiosteal dissection of muscles, transverse angled retractors locked in place, mainly right S2 laminectomy with high-speed drill, dissect nerve root from distal to proximal, monopolar stimulation for EMG or relay on CMAP recording, dissect and remove tumor, layered closure | Position prone, vertical midline incision over sacrum, fluoroscopy to confirm S1-2 level, drill and rongeurs to perform right-sided S1-2 laminectomy, identify right S1 nerve root within canal and exiting out S1-2 foramen, open dura overlying nerve root sleeve under microscope, follow tumor proximally to nerve root axilla to evaluate for intrathecal extension, internally debulk tumor and follow distally through S1-2 foramen, may need to unroof foramen to full extent, dissection and | Position prone, x-ray level check, midline incision at S2, subperiosteal muscle dissection to expose laminae, x-ray level check, S2 laminectomy using high-speed drill or ultrasonic bone cutter under microscopic visualization, dissection of presumed nerve sheath tumor, identify lesion and delimitation of edges, excision of lesion +/– nerve root sacrifice, send tissue for histology, dural closure with clips, dura | Position prone, IOM, localization x-ray, midline incision from S2-S4, subperiosteal exposure of S2-4 spinous process and lamina, localization x-ray, S2-4 laminectomies, dissection and identification of bilateral S2-4 nerve roots and tumor, isolate likely S4 nerve root, identify nerve proximal and distal to the tumor, ligate proximal aspect of S4 nerve root below thecal sac with 2-0 silk suture and then cut, cut S4 nerve root distal to tumor, deliver |
peel tumor capsule off of remaining fascicles, meticulous dural closure with fibrin glue, multilayer closure, horizontal mattress sutures in skin, immediate mobilization after surgery | repair with glue, layered closure, flat for 48 hours if CSF encountered | entire tumor in one piece, hemostasis with gentle irrigation, layered closure with attention to lumbosacral and Scarpa’s fascia with subfascial drain tunneled below lumbosacral fascia in rostral direction away from incision and carried out through separate stage incision, skin closure with glue | ||
Complication avoidance | Right hemilaminectomy, follow course of entire nerve from distal to proximal, monopolar stimulation and CMAP to identify nerve roots | Right hemilaminectomy, follow course of entire nerve, assess for intradural tumor, internally debulk tumor before peeling tumor from fascicles, fibrin glue, immediate mobilization after surgery | Follow course of entire nerve, identify beginning and termination, determine whether nerve needs to be sacrificed, flat for 48 hours if CSF encountered | Isolate nerve root where tumor is coming from, ligate and cut proximal nerve root first, en bloc tumor removal |
Postoperative | ||||
Admission | Floor | Floor | Floor | Floor |
Postoperative complications feared | Nerve root injury, CSF leak, epidural hematoma, infection | Nerve root palsy, pain, CSF leak, urinary retention, paralytic ileus | Nerve root injury causing incontinence or sexual dysfunction, CSF leak, infection | Urinary retention, persistent urinary tract infections, wound infection, CSF leak |
Anticipated length of stay | 2 days | 2–4 days | 5–7 days | 1–3 days |
Follow-up testing |
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MRI 3–4 months after surgery, then annually for 5 years | MRI 3 months, yearly for 2 years | MRI 6 weeks after surgery if en bloc achieved (<48 hours if subtotal resection), 6 months, 12 months, 24 months, 36 months after surgery |
Bracing | None | None | None | None |
Follow-up visits | 2 weeks, 4 months after surgery | 3 weeks, 6 weeks, 3–4 months after surgery | 6 weeks, 3 months, yearly for 2 years after surgery | 2 weeks, 6 weeks, 3 months, 6 months, 12 months, then annually after surgery |
Nerve sheath tumor
Metastasis
Chordoma
Tarlov cyst
Other primary bone tumor
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