Minimally invasive removal of lumbar intradural extramedullary lesions using the interlaminar approach

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OBJECT

Posterior midline laminectomy or hemilaminectomy has been successfully applied as the standard microsurgical technique for the treatment of spinal intradural pathologies. However, the associated risks of postoperative spinal instability increase the need for subsequent fusion surgery to prevent potential long-term spinal deformity. Continuous efforts have been made to minimize injuries to the surrounding tissue resulting from surgical manipulations. The authors report here their experiences with a novel minimally invasive surgical approach, namely the interlaminar approach, for the treatment of lumbar intraspinal tumors.

METHODS

A retrospective review was conducted of patients at the Second Affiliated Hospital of Zhejiang University School of Medicine who underwent minimally invasive resection of lumbar intradural-extramedullary tumors. By using an operative microscope, in addition to an endoscope when necessary, the authors were able to treat all patients with a unilateral, paramedian, bone-sparing interlaminar technique. Data including preoperative neurological status, tumor location, size, pathological diagnosis, extension of resections, intraoperative blood loss, length of hospital stay, and clinical outcomes were obtained through clinical and radiological examinations.

RESULTS

Eighteen patients diagnosed with lumbar intradural-extramedullary tumors were treated from October 2013 to March 2015 by this interlaminar technique. A microscope was used in 15 cases, and the remaining 3 cases were treated using a microscope as well as an endoscope. There were 14 schwannomas, 2 ependymomas, 1 epidermoid cyst, and 1 enterogenous cyst. Postoperative radiological follow-up revealed complete removal of all the lesions and no signs of bone defects in the lamina. At clinical follow-up, 14 of the 18 patients had less pain, and patients' motor/sensory functions improved or remained normal in all cases except 1.

CONClUSIONS

When meeting certain selection criteria, intradural-extramedullary lumbar tumors, especially schwannomas, can be completely and safely resected through a less-invasive interlaminar approach using a microscope, or a microscope in addition to an endoscope when necessary. This approach was advantageous because it caused even less bone destruction, resulting in better postoperative spinal stability, no need for facetectomy and fusion, and quicker functional recovery for the patients. Individualized surgical planning according to preoperative radiological findings is key to a successful microsurgical resection of these lesions through the interlaminar space.

ABBREVIATIONSASIA = American Spinal Injury Association; CISS = constructive interference in steady state; GTR = gross-total resection; VAS = visual analog scale; VRT = volume-rendering technique.

OBJECT

Posterior midline laminectomy or hemilaminectomy has been successfully applied as the standard microsurgical technique for the treatment of spinal intradural pathologies. However, the associated risks of postoperative spinal instability increase the need for subsequent fusion surgery to prevent potential long-term spinal deformity. Continuous efforts have been made to minimize injuries to the surrounding tissue resulting from surgical manipulations. The authors report here their experiences with a novel minimally invasive surgical approach, namely the interlaminar approach, for the treatment of lumbar intraspinal tumors.

METHODS

A retrospective review was conducted of patients at the Second Affiliated Hospital of Zhejiang University School of Medicine who underwent minimally invasive resection of lumbar intradural-extramedullary tumors. By using an operative microscope, in addition to an endoscope when necessary, the authors were able to treat all patients with a unilateral, paramedian, bone-sparing interlaminar technique. Data including preoperative neurological status, tumor location, size, pathological diagnosis, extension of resections, intraoperative blood loss, length of hospital stay, and clinical outcomes were obtained through clinical and radiological examinations.

RESULTS

Eighteen patients diagnosed with lumbar intradural-extramedullary tumors were treated from October 2013 to March 2015 by this interlaminar technique. A microscope was used in 15 cases, and the remaining 3 cases were treated using a microscope as well as an endoscope. There were 14 schwannomas, 2 ependymomas, 1 epidermoid cyst, and 1 enterogenous cyst. Postoperative radiological follow-up revealed complete removal of all the lesions and no signs of bone defects in the lamina. At clinical follow-up, 14 of the 18 patients had less pain, and patients' motor/sensory functions improved or remained normal in all cases except 1.

CONClUSIONS

When meeting certain selection criteria, intradural-extramedullary lumbar tumors, especially schwannomas, can be completely and safely resected through a less-invasive interlaminar approach using a microscope, or a microscope in addition to an endoscope when necessary. This approach was advantageous because it caused even less bone destruction, resulting in better postoperative spinal stability, no need for facetectomy and fusion, and quicker functional recovery for the patients. Individualized surgical planning according to preoperative radiological findings is key to a successful microsurgical resection of these lesions through the interlaminar space.

ABBREVIATIONSASIA = American Spinal Injury Association; CISS = constructive interference in steady state; GTR = gross-total resection; VAS = visual analog scale; VRT = volume-rendering technique.

Intraspinal tumors are lesions located either outside the spinal cord (intradural-extramedullary or extradural) or inside the spinal cord (intramedullary).43 The traditional surgical procedures for resection of these pathologies involve subperiosteal muscle stripping, hemilaminectomy, or even extensive laminectomy.46 For those lesions affecting the foraminal regions, an additional ipsilateral facetectomy might be required.13,24 Therefore, in view of the increased risks of spinal instability and deformities associated with these radical operations, especially when the cervical or lumbar spine is operated on, reconstructive fusion procedures are usually required.15,19,38,39,48 One unique anatomical feature of the lamina of the lumbar spine is its relatively wide wedge-shaped interlaminar space, widest at the center while narrowed at either end. To prevent the aforementioned complications, alternative, less-invasive surgical techniques are being developed by taking advantage of both the natural opening or passage in the bones of the spine and innovations in surgical instruments.37,49 The purpose of this present study was to report experiences with a novel minimally invasive technique, namely microsurgical resection of lumbar lesions via a “lossless” interlaminar approach. The authors use the word “lossless” to convey the concept of the most minimal injury ever possible to surrounding bony tissues while successfully removing the lesions in the spinal canal. This method is technically feasible for the following reasons: first, patients with intradural tumors at the lumbar spine usually manifest signs and symptoms in the early stages.32 And the availability of MR images also contribute to early detection of tumors, e.g., when the diameter is 2 cm or smaller. Second, schwannomas are the most common intradural-extramedullary spinal tumors that are found in the lumbar spine, and they typically do not adhere to surrounding spinal cord, nerves, or vessels, and are relatively easy to remove via microsurgical manipulation.27,30 Third, because of the absence of the spinal cord, the lumbar cistern is quite spacious. In addition, schwannomas usually have a downward blood supply that originates from the same artery feeding the affected spinal nerve root above.23 Therefore, exposure and coagulation of the feeding artery at the upper (proximal) edge of the tumor could effectively control tumor bleeding during the operation and thus may help to ensure a clear visual field under the microscope and reduce the risks of nerve injury as well.26 Lastly, both preoperative gradient-echo constructive interference in steady state (CISS) MRI sequencing and 3D CT reconstruction of the spinal canal with the volume-rendering technique (VRT) are helpful in terms of investigating the spatial relationship between the tumor and the affected spinal nerve root; therefore, precise surgical planning can be customized for each patient.9,16,25 By sparing the need for complete or even partial laminectomy and/or facetectomy and subsequent spinal fusion, the authors suggest that this novel, minimally invasive interlaminar treatment of intradural-extramedullary lumbar tumors could become increasingly popular in spinal surgery.

Methods

Study Population

A retrospective review was conducted of patients who underwent minimally invasive resection of lumbar intraspinal tumors between October 2013 and March 2015 in the Department of Neurosurgery, Second Affiliated Hospital of Zhejiang University School of Medicine. Approval for the study was obtained from the Medical Ethics Committee of the Second Affiliated Hospital of Zhejiang University School of Medicine. Preoperative evaluation consisted of clinical examination of the patient and contrast-enhanced MRI of the spine. Patient data including tumor location and size, pathological diagnosis, intraoperative blood loss, operative time, postoperative time to mobilization, duration of hospitalization, and postoperative complications were collected. The extent of resection was assessed during surgery and was confirmed by using postoperative spinal MRI. At the last follow-up, clinical outcome was assessed using the visual analog scale (VAS) for pain and the American Spinal Injury Association (ASIA) scale for motor/sensory outcome.

Operative Techniques

After receiving general anesthesia, the patient was placed prone with all pressure points padded. A 4-cm skin incision was made in the midline centered over the lamina where the intradural tumor was located. To fully use the natural opening of the interlaminar space, which is widest at the center, the contralateral laminar space was usually exposed. The interspinous ligament was kept intact. Para-spinous musculature was stripped subperiosteally with monopolar cauterization, and, after placement of a retractor, the hemilamina above and below the target interlaminar space and the ligamentum flavum were exposed.

Then the microscope was mounted and the contralateral ligamentum flavum was resected piecemeal with a Kerrison rongeur. The dura and the arachnoid membrane underneath were then dissected in a standard longitudinal fashion, and a 4–0 suture was placed to pull away the dura to form a working window of approximately 1.5–2.0 cm in diameter (Fig. 1A and E). The intradural pathology was resected using a standard microsurgical technique. First, the lesion was identified among the spinal nerves by using a microsurgical probe, and with the help of a microaspirator, a surgical plane was then developed between the lesion and the spinal nerves. Caution was taken to identify the affected spinal nerve at the apex of the lesion, and sometimes it had to be removed because of its adherence to the lesion. Coagulation and cut-off of the feeding artery could lead to decreased blood perfusion of the lesion and facilitate the identification and separation of the efferent spinal nerve at the lower end of the lesion. Once the lesion was gently dissected from the spinal nerve on both ends, it was removed using an en bloc technique (Fig. 1B). When necessary, the lesion was resected in a piecemeal fashion using an ultrasonic aspirator.

FIG. 1.
FIG. 1.

Photographs of the operative procedures. A: The contralateral ligamentum flavum of the Interlaminar space concerned was resected piecemeal with a Kerrison rongeur under the microscope. Usually the opening in the soft tissue was approximately 1.5–2.0 cm in diameter, depending on the size of the tumor underneath. B: Once the tumor was gently dissected from the spinal nerve on both upper and lower ends, it could then be removed by using an en bloc technique. C-E: The closure of the dura was achieved with application of titanium durai clips, and no incidence of postoperative CSF leak was observed. In the presented case, the opening measured less than 1 cm.

If the interlaminar space was relatively small and/or the upper and lower ends of the lesion were located too far away from the interlaminar space to be observed and manipulated directly under the microscope, the authors chose to use endoscopic instruments for better access to the lesions and to minimize potential damage to the spinal cord. Specifically, when a dura opening of approximately 1.0 cm in diameter was achieved under the microscope, a rigid endoscope was introduced through this working window and gently inserted into the contralateral subdural space. Isothermal normal saline (pressure at 100–150 mm H2O) was used to irrigate the operative field. A small piece of gelatin foam was then inserted to provide a surgical plane between the lesion and nerves. The feeding artery and affected spinal nerves were coagulated and dissected by using a bipolar flexible radiofrequency probe. If the tumors were too large to be pulled out directly through the endoscopic canal, the endoscope was removed, and the tumors were resected microscopically with an ultrasonic aspirator. Once the tumor was resected, the dura was closed with titanium dural clips (Fig. 1C–E), and the suture line was reinforced with fibrin glue or gelatin foam to prevent epidural bleeding. The retractor and microscope were removed, the fascia and muscle were reapproximated with a 2–0 resorbable suture, and the subdermal region was reapproximated with a 3–0 resorbable suture. The skin was closed with 4–0 resorbable sutures using the subcuticular closure technique.

Results

Between October 2013 and March 2015, a total of 18 patients diagnosed with lumbar intradural-extramedullary tumors underwent minimally invasive treatment at the Department of Neurosurgery, Second Affiliated Hospital of Zhejiang University School of Medicine via interlaminar techniques, including 3 cases with intraoperative endoscopic assistance (Table 1). There were 12 men and 6 women with a mean age of 50 years (range 35–64 years). Gross-total resection (GTR) was achieved in all 18 patients. The average duration of surgery was 128 minutes (range 60–315 minutes), and the mean blood loss was 47 ml (range 20–100 ml; Table 2). There was only 1 patient who had procedure-related complications (urinary incontinence), but he recovered within 3 weeks after surgery. No incidence of postoperative CSF leak was observed in our study. Pathological reports identified benign schwannomas in 14 patients, and 2 ependymomas, 1 epidermoid cyst, and 1 enterogenous cyst. All patients were mobilized within 24 hours after surgery, and the mean length of hospitalization was 13 days (range 7–20 days). The mean MRI and clinical follow-up were 3.5 months (range 1–12 months) and 4.9 months (range 1–16 months), respectively. At last follow-up, 14 of the 18 patients had a reduced level of pain as suggested by an average VAS score that improved from 4.3 to 0.3. The ASIA grade improved or remained normal in all patients except for 1 (Table 2).

TABLE 1.

Demographic data of the 18 patients who underwent minimally invasive resection of intradural-extramedullary lumbar tumors via an interlaminar approach

Case No.Age (yrs), SexLocationSize (mm)VAS ScoreNeurological Deficit (ASIA Grade)Duration of Symptoms (mos)
159, ML1–210 × 9 × 396E120
239, FL1–210 ×11 × 150E4
361, ML1–210 × 10 × 206E6
455, ML1–28 × 8 × 144E2
536, FL3–49 × 9 ×117E3
664, MT12–L118 × 15 × 597Myelopathy, D6
748, FL1–28 × 8 × 74E60
855, FL1–214 × 14 × 257Myelopathy, D2
942, ML3–414 × 12 × 206E3
1060, ML1–210 × 11 × 116E1
1149, MT12-L110 × 11 × 114E1
1246, ML-318 × 12 × 194E2
1344, FL3–412 × 12 × 154E4
1448, ML3–413 × 9 × 200E3
1551, ML3–417 × 13 × 186E7
1650, FL-27 × 7 × 100E1
1760, ML2–36 × 5 × 70E1
1835, ML3–49 × 12 × 336E24
TABLE 2.

Outcome of patients who underwent minimally invasive resection of intradural-extramedullary lumbar tumors via an interlaminar approach*

Case No.Pathological DiagnosisOp Time (mins)EBL (ml)LOS (days)Follow-Up (mos)VAS Score (preop/follow-up)ASIA Grade (preop/postop)Complications
ClinicalMRI
1Schwannoma905016336/0E/ENo
2Schwannoma110307530/0E/ENo
3Schwannoma905017536/0E/ENo
4Ependymoma (WHO Grade II)1405013534/0E/ENo
5Epidermoid cyst1002016437/1E/ENo
6Schwannoma23050204.537/1D/DUrinary incontinence
7Schwannoma125509534/0E/ENo
8Schwannoma110501127/1D/ENo
9Schwannoma7050111.56/0E/ENo
10Schwannoma31550172.56/1E/ENo
11Schwannoma1135015864/0E/ENo
12Schwannoma6020814/0E/ENo
13Schwannoma120501114/0E/ENo
14Schwannoma165301110/0E/ENo
15Schwannoma1005010866/0E/ENo
16Ependymoma (WHO Grade II)1005015960/0E/ENo
17Enterogenous cyst17010015660/0E/ENo
18Schwannoma100501516126/1E/ENo
EBL = estimated blood loss; LOS = length of stay.

All patients underwent GTR.

Illustrative Cases

Case 1

A 59-year-old man with no medical history of note complained of approximately 10 years of left lower-limb pain, which had aggravated him for 1 month. There was no history of gait disturbance or bowel or bladder dysfunction. On physical examination, no sensory or motor deficits were found. The patient underwent lumbar contrast-enhanced MRI, which revealed an intradural-extramedullary tumor with cystic change at the L1–2 level (Fig. 2A–D). The patient underwent microsurgical tumor removal via the interlaminar approach, and postoperative MRI scans verified GTR (Fig. 2E and F). VRT reconstruction verified the intactness of the spinal lamina (Fig. 2G and H). Pathological examination revealed the lesion to be a schwannoma. At follow-up, the patient's pain was completely resolved.

FIG. 2.
FIG. 2.

Case 1. A–D: Preoperative T1-weighted contrast-enhanced (A: sagittal; C: coronal; D: axial) and T2-weighted (B) MR images suggest an L1–2 intradural-extramedullary schwannoma. E and F: Postoperative sagittal T1-weighted contrast-enhanced (E) and T2-weighted (F) MR images verified GTR of the tumor. G: Preoperative 3D CT reconstruction of the spinal canal with VRT suggests that the lesion was accessible via the contralateral L1–2 interlaminar space (arrow). H: Postoperative VRT reconstruction verified the intactness of the spinal lamina (arrow).

Case 2

A 39-year-old woman with no medical history of note complained of approximately 4 months of stiffness in her right upper thigh. She had no history of gait disturbance or bowel or bladder dysfunction. On physical examination, no sensory or motor deficits were found. The patient underwent lumbar contrast-enhanced MRI, which revealed an intradural-extramedullary tumor at the L1–2 level (Fig. 3A–C). The patient underwent microsurgical tumor removal via the interlaminar approach, and postoperative MR images verified GTR (Fig. 3D). VRT reconstruction verified the intactness of the spinal lamina (Fig. 3E and F). Pathological examination revealed the lesion to be a schwannoma. At follow-up, the feeling of stiffness was completely resolved.

FIG. 3.
FIG. 3.

Case 2. A–C: Preoperative T1-weighted contrast-enhanced MR images (A: sagittal; B: coronal; C: axial) suggest an L1–2 intradural-extramedullary schwannoma. D: A postoperative sagittal T1-weighted contrast-enhanced MR image verified GTR of the tumor. E: Preoperative 3D CT reconstruction of the spinal canal with VRT suggests that the lesion was accessible via the contralateral L1–2 interlaminar space (arrow). F: Postoperative VRT reconstruction verified the intactness of the spinal lamina (arrow).

Case 10

A 60-year-old man with no medical history of note complained of approximately 1 month of right lower-limb pain. There was no history of gait disturbance or bowel or bladder dysfunction. On physical examination, sensory or motor deficits were not found. The patient underwent lumbar contrast-enhanced MRI, which revealed an intradural-extramedullary tumor at the L1–2 level and a herniated disk at the L4–5 level (Fig. 4A–C). The patient underwent removal of the tumor and the nucleus pulposus via endoscopic assistance, and postoperative MR images verified GTR (Fig. 4D). VRT reconstruction verified the intactness of the spinal lamina (Fig. 4E and F). Because the L1–2 interlaminar space was relatively small in the present case, instead of direct microsurgical resection, an endoscope was introduced into the dural opening to remove the tumor (Fig. 4G). Pathological examination revealed the lesion to be a schwannoma. At follow-up, the patient’s lower-limb pain was completely resolved.

FIG. 4.
FIG. 4.

Case 10. A–C: Preoperative T1-weighted contrast-enhanced MR images (A: sagittal; B: coronal; C: axial) suggest an L1–2 intradural-extramedullary schwannoma. D: A postoperative sagittal T1-weighted contrast-enhanced MR image verified GTR of the tumor. E: Preoperative 3D CT reconstruction of the spinal canal with VRT suggested that the lesion was accessible via the contralateral L1–2 interlaminar space (arrow). F: Postoperative VRT reconstruction verified the intactness of the spinal lamina (arrow). G: Because the L1–2 interlaminar space was relatively small in the present case, instead of direct microsurgical resection, an endoscope was introduced into the dura opening to expose (a), separate (b), coagulate (c), and then cut off (d) the tumor.

Discussion

Schwannomas are the most common intradural-extramedullary lesions of the lumbar spine, at approximately 50%, and they are mostly benign tumors of the nerve sheath that grow slowly and can be satisfactorily treated with GTR.1,3,7,17,18 A traditional approach to lumbar intradural schwannomas involves a midline incision, bilateral muscle dissection, and removal of the posterior spinal elements.2,3,6,14,33 Consequently, this approach might increase risks of postoperative spinal instability. Efforts have been made to improve the surgical technique from extensive laminectomy and facetectomy, to laminoplasty, hemilaminectomy, or even semihemilaminectomy.5,17,22,35,36,42 Although different surgical techniques have their own indications and contradictions, we should keep in mind that our priority sequence will always be the protection of the spinal cord and its function first, followed by prevention of postoperative spinal instability and deformity, and then minimization of the injuries to ligaments, muscle, and skin, if possible

The natural opening of the interlaminar space, especially the center portion, is actually wider than most of us had previously perceived. In Case 1, the tumor was located laterally under the interlaminar space. The classical surgical approach for its exposure is usually ipsilateral hemilaminectomy followed by partial or complete facetectomy. However, the authors chose the contralateral interlaminar approach to access this tumor instead. The advantage of this contralateral opening is full utilization of the widest center part of the interlaminar space for better exposure and resection of the lesion under a microscope. Therefore, this alternative minimally invasive interlaminar technique is expected to provide the same, if not better, protection to the spinal nerves as conventional techniques provide while maximally reducing bone tissue destruction.

In this series of 18 cases, 14 patients were pathologically diagnosed with benign schwannomas and the remaining 4 patients were diagnosed with 2 ependymomas, 1 epidermoid cyst, and 1 enterogenous cyst. Furthermore, the authors compared the results of the present study to results from their previous work reporting on semihemilaminectomy for the resection of a series of 24 intraspinal tumors.47 These previous data show that although there was no significant difference in tumor size between the 2 studies, the interlaminar procedure group had reduced intraoperative blood loss, postoperative confinement to bed, and length of hospitalization. In addition, the clinical outcome of the present series was comparable to outcomes with classic minimally invasive techniques.48

Spinal schwannoma are frequently associated with hemorrhage, intrinsic vascular changes, cyst formation, and fatty degeneration.10,20,21 In the rare cases of cystic spinal schwannomas, the solid component of the tumors can be quite small.31,45 In Case 2, the lesion was 3.0 cm along the long axis, which exceeded the width of the interlaminar space. Therefore, the initial surgical plan was to remove the tumor via 2 adjacent interlaminar spaces. However, after exposure of the tumor through 1 interlaminar space and successful discharge of its cystic component, the lesion shrunk dramatically, and it was then possible to resect the tumor via this single interlaminar space. Nevertheless, caution should still be taken, because in these patients the affected spinal nerve could be located distal to

The relatively spacious lumbar spine makes it possible to endoscopically manage intradural lesions through the natural interlaminar space. The major obstacles that prevent the introduction of full endoscopic resection of intradural tumors into clinical practice might be related to factors such as excessive heavy bleeding from the epidural venous plexus, which could cause blurred images during the course of endoscopic surgery, and technical difficulties such as opening/retracting/closing of the dura using a full endoscope.8,11,12,28,29,40,41 Accordingly, we modified the endoscopic surgery with microscope assistance; i.e., the endoscope was only introduced after the dura was opened and suspended under the microscope. For instance, in Cases 6, 10, and 14, where the affected spinal nerves were located distal to the skin incision, it was quite difficult to discern anatomical features under the microscope. In addition, in Case 10, the preoperative VRT reconstruction indicated that the interlaminar space was too small for direct microscopic resection. However, with the help of the intraoperative endoscope, all 3 tumors located distal to the interlaminar space were successfully removed.

Except for those large schwannomas and ependymomas that occur in the conus medullaris,4,34,44 the authors endorse the surgical removal of lumbar intraspinal tumors through the interlaminar space. The core surgical techniques include the following: first, a strict selection criterion should be imposed in preoperative surgical planning. The indications for the interlaminar approach are those lumbar tumors that were revealed by preoperative radiological examinations to be small and oval to spindle shaped, or relatively large but with a significant cystic component. If the solid component of the lesion had a transverse diameter exceeding three-fourths of the diameter of the spinal canal, then it would be quite difficult to develop a surgical plane, significantly increasing the risks of spinal nerve injuries. Therefore, under such circumstances, we suggest the use of hemilaminectomy instead. Second, preoperative 3D CT reconstruction of the spinal canal with VRT might generate important anatomical information about the interlaminar space in question and allow emulation of the working conditions under a microscope. Third, CISS MRI sequences are helpful for determining the spatial relationship between the tumor and the affected spinal nerve root and are thus quite valuable for preoperative planning. Fourth, priority should be given to exposure and coagulation of the feeding artery at the upper (proximal) edge of the tumor during the operation. Because schwannomas generally rely on this downward blood supply for growth, this manipulation could effectively control tumor bleeding, render it possible for en bloc piecemeal tumor resec tion, or move the lesion to the next interlaminar space for excision. Finally, if difficulties appear during the operation, such as firm adhesion of the tumor to its surrounding spinal nerves, it would be reasonable to switch to a hemilaminectomy or laminectomy to minimize the risk of spinal nerve injury.

Conclusions

Most of the lumbar intraspinal tumors, especially schwannomas, could be safely and completely resected via a bone-sparing interlaminar approach. The indications for this novel approach (selection criteria) are lumbar tumors located near the interlaminar space and, according to preoperative radiological examinations, measuring less than 2 cm at the long axis diameter, or even more than 3 cm when a significant cystic component is present. With the aim to better protect neurological function, surgical planning should be individualized according to the anatomical features of the interlaminar space, and the tumor underneath should undergo thorough preoperative radiological characterization.

Author Contributions

Conception and design: YJ Zhu, Shen. Acquisition of data: YJ Zhu, Ying, Chen, LL Wang, Ren, C Wang. Analysis and interpretation of data: YJ Zhu, Ying, Chen, LL Wang, Shen. Drafting the article: YJ Zhu, Shen. Critically revising the article: Zhang. Administrative/technical/material support: LL Zhu, Wu. Study supervision: LL Zhu, Zhang.

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    • Export Citation
  • 26

    Mannion RJNowitzke AMEfendy JWood MJ: Safety and efficacy of intradural extramedullary spinal tumor removal using a minimally invasive approach. Neurosurgery 68:1 Suppl Operative2082162011

    • Search Google Scholar
    • Export Citation
  • 27

    Marchetti MDe Martin EMilanesi IFariselli L: Intradural extramedullary benign spinal lesions radiosurgery. Medium-to long-term results from a single institution experience. Acta Neurochir (Wien) 155:121512222013

    • Search Google Scholar
    • Export Citation
  • 28

    Mauer UMGottschalk AKunz USchulz C: Arachnoscopy: a special application of spinal intradural endoscopy. Neurosurg Focus 30:4E72011

    • Search Google Scholar
    • Export Citation
  • 29

    Maxmauer UDanz BGottschalk AKunz U: Endoscope-assisted surgery of spinal intradural adhesions in the presence of cerebrospinal fluid flow obstruction. Spine (Phila Pa 1976) 36:E773E7792011

    • Search Google Scholar
    • Export Citation
  • 30

    Mehta AIAdogwa OKarikari IOThompson PVerla TNull UT: Anatomical location dictating major surgical complications for intradural extramedullary spinal tumors: a 10-year single-institutional experience. J Neurosurg Spine 19:7017072013

    • Search Google Scholar
    • Export Citation
  • 31

    Netra RHui MSGang MZMing Z: Spinal cystic schwannoma: an MRI evaluation. J Coll Physicians Surg Pak 24:1451472014

  • 32

    Ozawa HOnoda YAizawa TNakamura TKoakutsu TItoi E: Natural history of intradural-extramedullary spinal cord tumors. Acta Neurol Belg 112:2652702012

    • Search Google Scholar
    • Export Citation
  • 33

    Sachdev SDodd RLChang SDSoltys SGAdler JRLuxton G: Stereotactic radiosurgery yields long-term control for benign intradural, extramedullary spinal tumors. Neurosurgery 69:5335392011

    • Search Google Scholar
    • Export Citation
  • 34

    Sasani MSasani HKaner TFahir Ozer A: Resection of a large spinal intradural ependymoma using a limited unilateral laminectomy approach in the lumbosacral region. J Neurosurg Sci 56:55592012

    • Search Google Scholar
    • Export Citation
  • 35

    Sharifi GMortaz MParsaei B: Multiple intradural extramedullary tumours presenting with paraplegia after trauma. Acta Neurochir (Wien) 151:6976982009

    • Search Google Scholar
    • Export Citation
  • 36

    Sim JENoh SJSong YJKim HD: Removal of intradural-extramedullary spinal cord tumors with unilateral limited laminectomy. J Korean Neurosurg Soc 43:2322362008

    • Search Google Scholar
    • Export Citation
  • 37

    Smith ZAAoun SGY El Ahmadieh TWong APLall RRBendok BR: Minimally invasive resection of a high-thoracic intradural extramedullary tumor: an operative 3-D video. Neurosurgery 73:1 Suppl Operativeons12013. (Erratum in Neurosurgery 73:E913 2013)

    • Search Google Scholar
    • Export Citation
  • 38

    Tan LAKasliwal MKWewel JFontes RBO'Toole JE: Minimally invasive surgery for synchronous, same-level lumbar intradural-extramedullary neoplasm and acute disc herniation. Neurosurg Focus 37:Suppl 2Video 162014

    • Search Google Scholar
    • Export Citation
  • 39

    Tarantino RDonnarumma PNigro LRullo MSantoro ADelfini R: Surgery of intradural extramedullary tumors: retrospective analysis of 107 cases. Neurosurgery 75:5095142014

    • Search Google Scholar
    • Export Citation
  • 40

    Thongrong CKasemsiri PCarrau RLBergese SD: Control of bleeding in endoscopic skull base surgery: current concepts to improve hemostasis. ISRN Surg 2013:1915432013

    • Search Google Scholar
    • Export Citation
  • 41

    Tredway TLMusleh WChristie SDKhavkin YFessler RGCurry DJ: A novel minimally invasive technique for spinal cord untethering. Neurosurgery 60:2 Suppl 1ONS70ONS742007

    • Search Google Scholar
    • Export Citation
  • 42

    Tredway TLSantiago PHrubes MRSong JKChristie SDFessler RG: Minimally invasive resection of intradural-extramedullary spinal neoplasms. Neurosurgery 58:1 SupplONS52ONS582006

    • Search Google Scholar
    • Export Citation
  • 43

    Weber CGulati SJakola ASHabiba SNygaard OPJohannesen TB: Incidence rates and surgery of primary intraspinal tumors in the era of modern neuroimaging: a national population-based study. Spine (Phila Pa 1976) 39:E967E9732014

    • Search Google Scholar
    • Export Citation
  • 44

    Wostrack MShiban EObermueller TGempt JMeyer BRingel F: Conus medullaris and cauda equina tumors: clinical presentation, prognosis, and outcome after surgical treatment: clinical article. J Neurosurg Spine 20:3353432014

    • Search Google Scholar
    • Export Citation
  • 45

    Wu DBa ZHuang YZhao WShen BKan H: Totally cystic schwannoma of the lumbar spine. Orthopedics 36:e679e6822013

  • 46

    Yu YZhang XHu FXie TGu Y: Minimally invasive microsurgical treatment of cervical intraspinal extramedullary tumors. J Clin Neurosci 18:116811732011

    • Search Google Scholar
    • Export Citation
  • 47

    Zhu YJTang ZXWang LLZhu LLShen HZhang JM: Microsurgical resection of spinal intradural extramedullary tumors by hemi-semi-laminectomy. Chinese J Neurosurg 30:6946972014

    • Search Google Scholar
    • Export Citation
  • 48

    Zong SZeng GDu LFang YGao TZhao J: Treatment results in the different surgery of intradural extramedullary tumor of 122 cases. PLoS One 9:e1114952014

    • Search Google Scholar
    • Export Citation
  • 49

    Zong SZeng GXiong CWei B: Treatment results in the differential surgery of intradural extramedullary schwannoma of 110 cases. PLoS One 8:e638672013

    • Search Google Scholar
    • Export Citation

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Article Information

Contributor Notes

Correspondence Yong-Jian Zhu, Department of Neurosurgery, Second Affiliated Hospital of Zhejiang University School of Medicine, 88 Jiefang Rd., Hangzhou, Zhejiang 310000, China. email: neurosurgery@zju.edu.cn.* Drs. G. Y. Ying and F. Shen contributed equally to this work.INCLUSE WHEN CITING DOI: 10.3171/2015.5.FOCUS15182.DISCLOSURE This study was supported by the Science and Technology Department of Zhejiang Province (grant no. 2007C33042) and Ningbo Key Clinical Specialty (Orthopedics; grant no. 2013–88).

© AANS, except where prohibited by US copyright law.

Headings
Figures
  • View in gallery

    Photographs of the operative procedures. A: The contralateral ligamentum flavum of the Interlaminar space concerned was resected piecemeal with a Kerrison rongeur under the microscope. Usually the opening in the soft tissue was approximately 1.5–2.0 cm in diameter, depending on the size of the tumor underneath. B: Once the tumor was gently dissected from the spinal nerve on both upper and lower ends, it could then be removed by using an en bloc technique. C-E: The closure of the dura was achieved with application of titanium durai clips, and no incidence of postoperative CSF leak was observed. In the presented case, the opening measured less than 1 cm.

  • View in gallery

    Case 1. A–D: Preoperative T1-weighted contrast-enhanced (A: sagittal; C: coronal; D: axial) and T2-weighted (B) MR images suggest an L1–2 intradural-extramedullary schwannoma. E and F: Postoperative sagittal T1-weighted contrast-enhanced (E) and T2-weighted (F) MR images verified GTR of the tumor. G: Preoperative 3D CT reconstruction of the spinal canal with VRT suggests that the lesion was accessible via the contralateral L1–2 interlaminar space (arrow). H: Postoperative VRT reconstruction verified the intactness of the spinal lamina (arrow).

  • View in gallery

    Case 2. A–C: Preoperative T1-weighted contrast-enhanced MR images (A: sagittal; B: coronal; C: axial) suggest an L1–2 intradural-extramedullary schwannoma. D: A postoperative sagittal T1-weighted contrast-enhanced MR image verified GTR of the tumor. E: Preoperative 3D CT reconstruction of the spinal canal with VRT suggests that the lesion was accessible via the contralateral L1–2 interlaminar space (arrow). F: Postoperative VRT reconstruction verified the intactness of the spinal lamina (arrow).

  • View in gallery

    Case 10. A–C: Preoperative T1-weighted contrast-enhanced MR images (A: sagittal; B: coronal; C: axial) suggest an L1–2 intradural-extramedullary schwannoma. D: A postoperative sagittal T1-weighted contrast-enhanced MR image verified GTR of the tumor. E: Preoperative 3D CT reconstruction of the spinal canal with VRT suggested that the lesion was accessible via the contralateral L1–2 interlaminar space (arrow). F: Postoperative VRT reconstruction verified the intactness of the spinal lamina (arrow). G: Because the L1–2 interlaminar space was relatively small in the present case, instead of direct microsurgical resection, an endoscope was introduced into the dura opening to expose (a), separate (b), coagulate (c), and then cut off (d) the tumor.

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    Mannion RJNowitzke AMEfendy JWood MJ: Safety and efficacy of intradural extramedullary spinal tumor removal using a minimally invasive approach. Neurosurgery 68:1 Suppl Operative2082162011

    • Search Google Scholar
    • Export Citation
  • 27

    Marchetti MDe Martin EMilanesi IFariselli L: Intradural extramedullary benign spinal lesions radiosurgery. Medium-to long-term results from a single institution experience. Acta Neurochir (Wien) 155:121512222013

    • Search Google Scholar
    • Export Citation
  • 28

    Mauer UMGottschalk AKunz USchulz C: Arachnoscopy: a special application of spinal intradural endoscopy. Neurosurg Focus 30:4E72011

    • Search Google Scholar
    • Export Citation
  • 29

    Maxmauer UDanz BGottschalk AKunz U: Endoscope-assisted surgery of spinal intradural adhesions in the presence of cerebrospinal fluid flow obstruction. Spine (Phila Pa 1976) 36:E773E7792011

    • Search Google Scholar
    • Export Citation
  • 30

    Mehta AIAdogwa OKarikari IOThompson PVerla TNull UT: Anatomical location dictating major surgical complications for intradural extramedullary spinal tumors: a 10-year single-institutional experience. J Neurosurg Spine 19:7017072013

    • Search Google Scholar
    • Export Citation
  • 31

    Netra RHui MSGang MZMing Z: Spinal cystic schwannoma: an MRI evaluation. J Coll Physicians Surg Pak 24:1451472014

  • 32

    Ozawa HOnoda YAizawa TNakamura TKoakutsu TItoi E: Natural history of intradural-extramedullary spinal cord tumors. Acta Neurol Belg 112:2652702012

    • Search Google Scholar
    • Export Citation
  • 33

    Sachdev SDodd RLChang SDSoltys SGAdler JRLuxton G: Stereotactic radiosurgery yields long-term control for benign intradural, extramedullary spinal tumors. Neurosurgery 69:5335392011

    • Search Google Scholar
    • Export Citation
  • 34

    Sasani MSasani HKaner TFahir Ozer A: Resection of a large spinal intradural ependymoma using a limited unilateral laminectomy approach in the lumbosacral region. J Neurosurg Sci 56:55592012

    • Search Google Scholar
    • Export Citation
  • 35

    Sharifi GMortaz MParsaei B: Multiple intradural extramedullary tumours presenting with paraplegia after trauma. Acta Neurochir (Wien) 151:6976982009

    • Search Google Scholar
    • Export Citation
  • 36

    Sim JENoh SJSong YJKim HD: Removal of intradural-extramedullary spinal cord tumors with unilateral limited laminectomy. J Korean Neurosurg Soc 43:2322362008

    • Search Google Scholar
    • Export Citation
  • 37

    Smith ZAAoun SGY El Ahmadieh TWong APLall RRBendok BR: Minimally invasive resection of a high-thoracic intradural extramedullary tumor: an operative 3-D video. Neurosurgery 73:1 Suppl Operativeons12013. (Erratum in Neurosurgery 73:E913 2013)

    • Search Google Scholar
    • Export Citation
  • 38

    Tan LAKasliwal MKWewel JFontes RBO'Toole JE: Minimally invasive surgery for synchronous, same-level lumbar intradural-extramedullary neoplasm and acute disc herniation. Neurosurg Focus 37:Suppl 2Video 162014

    • Search Google Scholar
    • Export Citation
  • 39

    Tarantino RDonnarumma PNigro LRullo MSantoro ADelfini R: Surgery of intradural extramedullary tumors: retrospective analysis of 107 cases. Neurosurgery 75:5095142014

    • Search Google Scholar
    • Export Citation
  • 40

    Thongrong CKasemsiri PCarrau RLBergese SD: Control of bleeding in endoscopic skull base surgery: current concepts to improve hemostasis. ISRN Surg 2013:1915432013

    • Search Google Scholar
    • Export Citation
  • 41

    Tredway TLMusleh WChristie SDKhavkin YFessler RGCurry DJ: A novel minimally invasive technique for spinal cord untethering. Neurosurgery 60:2 Suppl 1ONS70ONS742007

    • Search Google Scholar
    • Export Citation
  • 42

    Tredway TLSantiago PHrubes MRSong JKChristie SDFessler RG: Minimally invasive resection of intradural-extramedullary spinal neoplasms. Neurosurgery 58:1 SupplONS52ONS582006

    • Search Google Scholar
    • Export Citation
  • 43

    Weber CGulati SJakola ASHabiba SNygaard OPJohannesen TB: Incidence rates and surgery of primary intraspinal tumors in the era of modern neuroimaging: a national population-based study. Spine (Phila Pa 1976) 39:E967E9732014

    • Search Google Scholar
    • Export Citation
  • 44

    Wostrack MShiban EObermueller TGempt JMeyer BRingel F: Conus medullaris and cauda equina tumors: clinical presentation, prognosis, and outcome after surgical treatment: clinical article. J Neurosurg Spine 20:3353432014

    • Search Google Scholar
    • Export Citation
  • 45

    Wu DBa ZHuang YZhao WShen BKan H: Totally cystic schwannoma of the lumbar spine. Orthopedics 36:e679e6822013

  • 46

    Yu YZhang XHu FXie TGu Y: Minimally invasive microsurgical treatment of cervical intraspinal extramedullary tumors. J Clin Neurosci 18:116811732011

    • Search Google Scholar
    • Export Citation
  • 47

    Zhu YJTang ZXWang LLZhu LLShen HZhang JM: Microsurgical resection of spinal intradural extramedullary tumors by hemi-semi-laminectomy. Chinese J Neurosurg 30:6946972014

    • Search Google Scholar
    • Export Citation
  • 48

    Zong SZeng GDu LFang YGao TZhao J: Treatment results in the different surgery of intradural extramedullary tumor of 122 cases. PLoS One 9:e1114952014

    • Search Google Scholar
    • Export Citation
  • 49

    Zong SZeng GXiong CWei B: Treatment results in the differential surgery of intradural extramedullary schwannoma of 110 cases. PLoS One 8:e638672013

    • Search Google Scholar
    • Export Citation
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