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|NI FEATURE: CENTS (CONCEPTS, ERGONOMICS, NUANCES, THERBLIGS, SHORTCOMINGS) - ORIGINAL ARTICLE
|Year : 2015 | Volume
| Issue : 2 | Page : 230-236
Unilateral hemilaminectomy: The surgical approach of choice for juxta-medullary spinal tumors
Sandeep Mohindra, Amey Savardekar
Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India
|Date of Web Publication||5-May-2015|
Dr. Sandeep Mohindra
Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh
Source of Support: None, Conflict of Interest: None
Background: The conventional laminectomy may precipitate numerous long-term complications such as the development of kypho-scoliosis, spinal instability, epidural fibrosis and loss of bony shield over the spinal cord, thus increasing the risk of a subsequent myelopathy. The present study evaluates the efficacy of a unilateral hemilaminectomy as the surgical approach of choice for excision of juxtamedullary spinal neoplasms.
Materials and Methods: From January 2001 to December 2010, 83 patients (male: female ratio: 58: 25, mean age 37.4 years, median age 45 years) harboring a juxta-medullary spinal neoplasm were managed at our center. The radiological investigations included a contrast-enhanced magnetic resonance imaging (MRI) scan, (in the axial, sagittal and coronal planes). A high speed drill and an operating microscope assisted in the microsurgical excision of these neoplasms. During follow-up, MRI scans were obtained to check for any residual tumor.
Results: Complete tumor excision was achieved for all patients. At a mean follow-up of 17.6 months, the patients had improved to a better clinical status. The immediate postoperative complications in the form of paraparesis and cerebrospinal fluid leak were seen in 1 patient each, respectively; while none of the patients either developed post-operative spinal instability or required conversion of the hemilaminectomy to a conventional full laminectomy.
Conclusion: A unilateral hemilaminectomy is recommended as the microsurgical approach of choice for juxtamedullary spinal neoplasms.
Keywords: Juxta-medullary tumours; MRI scan; hemi-laminectomy; outcome
|How to cite this article:|
Mohindra S, Savardekar A. Unilateral hemilaminectomy: The surgical approach of choice for juxta-medullary spinal tumors. Neurol India 2015;63:230-6
| » Introduction|| |
The post-laminectomy long-term sequel including the development of spinal instability, kyphoscoliosisis and epidural fibrosis (due to extensive damage to the ligaments and the inter-vertebral joints) are well known. In principle, a unilateral approach to the spinal canal circumvents almost all such complications. However, apprehensions regarding incomplete tumor removal or inadvertent cord damage continue to prevent surgeons from enthusiastically adopting the latter approach. Recent advances in microsurgical techniques and in the microsurgical equipment have overcome the obstacles of a relatively narrow surgical corridor encountered in patients undergoing a unilateral approach.
In the present case series, the authors present a decade-long experience in the unilateral approach for juxtamedullary neoplasms (JMNs) of the spinal canal. A single surgeon (the senior author) has operated on all the patients included in this study at a single neurosurgical center.
| » Materials and Methods|| |
Patient population: A total of 83 patients harboring a JMN underwent surgical intervention from January 2001 to December 2010. There were 58 male and 25 female patients. Their age ranged from 14 years to 92 years (mean 37.4 years, median 45 years) with a slight preponderance of patients older than 50 years (54%). Seven patients (9%) were less than 20 years in age.
Clinical symptomatology: All patients presented with radicular pain and sensori-motor disturbances in the extremities. Clinical complaints attributable to compressive myelopathy were noted in almost all cases harboring a JMN cranial to the dorso-lumbar levels. Neurogenic disorders of micturition were noted in 25.4% of the total patients (n = 21) [Table 1].
|Table 1: Profile of patients operated for JMNs via a unilateral hemilaminectomy approach |
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Radiology: All patients underwent a preoperative contrast-enhanced magnetic resonance (MRI) scan [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]. Multiple tumors were noted only in 2 patients who had a neurofibromatosis (NF) 1 syndrome. Seven patients had a JMN large enough to enable their palpation in the neck. These tumors had grown through a widened intervertebral foramen. We removed these neck masses via an anterior approach after disconnecting them using the posterior approach. Along with axial and sagittal sections, the authors also preferred to have a coronal MRI in every case that clearly defined the site of the pathology and helped in deciding the side of the surgical exposure [Figure 1]d, [Figure 3]b, and [Figure 5]c. After a careful radiographic identification of the level at which the lesion was located, the anesthetized patients were positioned prone (on an arch bar for lesions located at the level of the lower thoracic and lumbar spine; or, with their head fixed to a 4-pin head fixator in the cases with cervical and cervico-thoracic lesions).
|Figure 1: Sagittal section of plain (a), contrast-enhanced (b), T2-weighted (c) magnetic resonance imaging (MRI) scan of the cervical spine showing the ventrally placed intradural, extramedullary tumor extending from foramen magnum to C5. The tumor is intensely is contrast-enhancing and is located more towards the right as noted in the coronal section of contrast-enhanced MRI scan (d). Axial section of contrast-enhanced MRI (e), T2-weighted, axial section (f and g) showing the right-sided lesion with cord displaced to the left|
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|Figure 2: Sagittal section of contrast-enhanced (a) and T2-weighted (b) magnetic resonance imaging scan showing no residual or recurrent lesion at 1-year of follow-up|
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|Figure 3: Sagittal (a), coronal (b) section of contrast-enhanced and T2-weighted (c) sagittal magnetic resonance imaging scan showing the contrast-enhanced, dorsally placed, juxtamedullary lesion at D6 and D7 levels|
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|Figure 4: Sagittal section, contrast-enhanced (a) and T2-weighted (b); axial section (c) of magnetic resonance imaging scan showing no evidence of residual or recurrent tumor at 3 years of follow-up. Axial section of computed tomography scan (d) at D6 level showing the amount of bony lamina drilled out for surgical exposure|
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|Figure 5: Sagittal section of contrast (a) and T2-weighted (b) magnetic resonance imaging (MRI) scan showing the juxtamedullary neoplasm at D3, D4, D5 levels. Axial section of contrast (c) and T2-weighted (d) MRI scan showing a left sided neoplasm with a central cystic component. At 3 years of follow-up, axial section of MRI scan (e), and computed tomography scan (f) shows no recurrent or residual lesion|
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|Figure 6: T2-weighted sagittal section (a), contrast-enhanced sagittal section (b), and, coronal section (c) showing the juxtamedullary neoplasm at D11, D12 and L1 levels. Follow-up magnetic resonance imaging scan, T2-weighted image (d) at 3 years shows no evidence of residual or recurrent lesion|
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|Figure 7: Sagittal section of contrast-enhanced (a), T2-weighted (b), axial section of contrast-enhanced (c) magnetic resonance imaging scan showing the cystic juxtamedullary neoplasm on the left side of the cervical cord at C7 level. Schematic representation (d) of the extent of the required bony removal and the appropriate placement of hemi-laminectomy retractors is shown. Axial computed tomography scan (e) showing the extent of hemi-laminectomy. Under-cutting of the base of the spinous process to obtain a maximal surgical exposure is recommended|
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Surgical technique: A midline skin incision was made and the fascia on the affected side was opened [Figure 9]a. Using a cutting cautery, a sharp dissection was carried out to detach the ipsilateral paravertebral muscles from the vertebral spinous processes and laminae. A rolled dry gauze further helped in detaching the tendinous attachments of the paraspinal muscles and helped in exposing the ipsilateral bony lamina and the spinous process [Figure 9]b. We routinely employed a hemi-laminectomy retractor for adequate exposure of the lamina and base of the spinous process [Figure 7]d and [Figure 8]. Under microscopic magnification, the unilateral lamina was drilled using a high-speed cutting burr. Initially, larger-sized cutting burrs were utilized, that were subsequently changed to the smaller sized ones to clear the bony hoods at the margins of the dural exposure. Edges of the bony corridor were smoothened by a diamond burr in 43 patients. Crude to fine rongeurs were also utilized for bony exposure. Extensive removal of the ligamentum flavum was done to gain maximal dural exposure [Figure 10]a. The articular processes were usually preserved but had to be excised in 14 patients. Undercutting of base of the spinous processes and an oblique tilting of the operating table to the contralateral side aided in providing an adequate visualization of the dural sac and augmented the exposure of the surgical field [Figure 4]d, [Figure 6]f, [Figure 7]e. The usual dural exposure was 15 mm wide for facilitating resection of tumors that were occupying one to two vertebral segments, while the cranio-caudal exposure depended upon the longitudinal extent of the JMNs. The cranial (n = 8) and caudal limits (n = 6) of the tumors were not accessible in 14 patients (which was discovered after the durotomy had been performed). Thus, extension of the bony removal in the cranio-caudal axis was required in these cases. The linear dural opening was always paramedian in location and the edges were tagged using a 3-0 non-braided suture [Figure 10]b. The cranial and caudal limits of the JMNs were defined [Figure 7]a, [Figure 7]b, [Figure 7]c. En-bloc tumor excision was performed only in 17 patients [Figure 7]a, [Figure 7]b, [Figure 7]c, [Figure 10]b while the rest [Figure 1]a - [Figure 1]g, [Figure 3]a - [Figure 3]c underwent an intra-tumoral de-bulking using micro-curettes or an ultrasonic surgical aspirator. In cases of a schwannoma, after identifying the involved parent nerve root, its fibers attached to the tumor were carefully sectioned. Hemostasis was usually not a problem and egress of free flow of cerebrospinal fluid (CSF) from both the cranial and caudal sides confirmed total tumor excision [Figure 11]a. Tumor debulking, tapping of its cystic component, and lateral tacking of the dural edges with the muscle or fascia near the facet joints were helpful maneuvers in delivering the tumor. The dural closure was achieved with interrupted knots using prolene monofilament 5-0 or 6-0 sutures [Figure 11]b. We did not use a dural sealant in any of our cases. On removing the self-retaining hemi-laminectomy retractors, the paravertebral muscles and fascia retraced back to their normal anatomical positions. The apposing edges of fascia were sutured with interrupted, absorbable 2-0 vicryl sutures. The subcutaneous tissue closure was performed in two layers without a wound drain, while the skin edges were approximated with steel staplers. The total duration of surgery ranged from 40 minutes to 120 minutes with a mean of 55 minutes.
|Figure 8: (a) Intra - operative picture showing the incised subcutaneous areolar tissue and the dissection reaching till tip of spinous processes. (b) Exposure of unilateral lamina after dissection of paraspinal muscles, with retractors in-situ|
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|Figure 9: Hemi-laminectomy retractors (a-c) showing two different sized and shaped flanges. Intraoperative picture (d) demonstrating the technique of placement of these retractors and the bony exposure|
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|Figure 10: Dural exposure after a 3-level hemilaminectomy (a). Delivery of tumor after placing tagging sutures at dural edges (b)|
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|Figure 11: (a) The nerve roots and contralaterally displaced cord after complete tumor excision. (b) Interlocking prolene sutures for dural closure|
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| » Results|| |
A total of 83 patients underwent microsurgical excision through a unilateral hemi-laminectomy approach. All tumors were excised successfully without damaging the cord or compromising the major osteoligamentous complex in the midline of the spine. The commonest location of the tumor was in the thoracic spine (n = 28, 33.7%) and majority of the lesions vertically spanned two spinal levels (n = 53). The histopathology of the JMNs was a schwannoma in 63.9% patients (n = 53). The follow up MRI scans [available in 73.5% (n = 61) patients] revealed total excision in all these patients [Figure 2]a, [Figure 2]b, [Figure 4]a, [Figure 4]b, [Figure 4]c, [Figure 5]d, [Figure 6]e. The immediate postoperative complications included paraparesis (n = 1) and CSF leak (n = 1). The follow-up ranged from 6 to 87 months with a mean of 17.6 months. We did not encounter postoperative spinal instability in any of our patients. None of our patients had a recurrence at follow up. An intra-operative conversion to a conventional laminectomy was not required in any of our cases.
| » Discussion|| |
Rationale for a unilateral hemilaminectomy
Traditionally, microsurgical excision of JMNs is undertaken through a total laminectomy. This approach remains popular as surgeons are familiar with this approach and a wide surgical exposure is achieved. The long-term follow-up of patients who have undergone a laminectomy has highlighted its association with several complications such as spinal deformity, instability, epidural fibrosis and loss of bony shield over the thecal sac and the spinal cord that increases the risk of myelopathy. , Post-laminectomy kyphoscoliosis is a major problem which may develop after weeks-to-years following the laminectomy (especially when performed in children before bone maturity is attained).  Musculo-ligamentous insufficiency due to their surgical stripping and denervation of the posterior paraspinal muscle complex is usually responsible for the post-laminectomy kyphosis.  The age of the patient, site and extent of laminectomy, performance of a concomitant facetectomy, and the inability to preserve ligamentous attachments along the spinous processes and laminae, are factors that influence the development of post-laminectomy spinal deformities. ,,,
A unilateral hemilaminectomy aims to obtain an adequate exposure of the offending lesion, enabling it to be excised completely without damaging the underlying spinal cord and the surrounding nerve roots; and, to help in preserving spinal column stability. This approach avoids damage to the interspinous ligaments and the intervertebral joints by completely preserving the sanctity of the contralateral para-vertebral musculature and ligaments. , The extent of exposure of the dorsal cord by a hemi-laminectomy is the same as that obtained after a conventional laminectomy [Figure 4]d, [Figure 6]f, [Figure 7]d, [Figure 7]e, [Figure 8]d. Literature has described the unilateral approach to be more advantageous than a bilateral approach for excision of juxtamedullary tumors. ,
The preoperative determination of the exact tumor location using an MRI is mandatory for a unilateral spinal approach as the durotomy only exposes the tumor and the normal cord is usually not visible until the tumor is nearly completely removed [Figure 11]a.  The coronal sections of contrast-enhanced MRI help in determining the side of the unilateral approach. Coronal sections of MRI were available in 89.2% (n = 74) patients in the present series. Meticulous microsurgical techniques further added to the safety of this approach. Some of the tumors may arise from the ventral roots. Thus, there is need for their meticulous preservation during tumor removal. Conversion of an unilateral laminectomy to a complete one is always an option that may be exercised in the interest of the patients' safety; however, it was not required in any of our patients.
A subperiosteal dissection using a monopolar 'cutting' cautery prevents tissue damage and provides a precise bony exposure [Figure 8]d. For all cases, we used a self-retaining hemi-laminectomy retractor which has two different sized and shaped arms [Figure a-c]. The lateral flange has a flat retractor for retracting the paraspinal muscles, while the medial one has a pointed retractor that hooks against the spinous process [Figure 8]d. Both the right and left sided retractors are employed simultaneously for providing an adequate exposure.
High-speed cutting burrs, ranging from thick burrs to as thin as a 2 mm sized one, may be used to smoothen the bony corridors.  Kerrison's ronguers of more than 2 mm size should be avoided to prevent an inadvertent cord damage. This is especially because the CSF cushion at the tumor site is usually obliterated due to the compression of the cord by the tumor. After a wide stripping-off of the ligamentum flavum,  the opened dura should be cautiously inspected under microscopic vision.  The tumor has a distinctively darker colour than the dural edges. We strongly advocate debulking of larger (greater than 2 cm) sized tumors using an ultrasonic aspirator or micro-currettes while stabilizing the tumor capsule with a tissue forceps [Figure 1]a - [Figure 1]g. En-bloc tumor excision is possible only in the cases having smaller lesions. The narrower bony corridor of this approach hinders their en-bloc delivery. Their manipulation, while attempting an en-bloc resection may damage the underlying cord.  Excision of the schwannomas is easier than that of meningiomas. The former are usually delivered out by CSF pulsations while meningiomas, being attached to the dura, may only be excised safely in a piecemeal manner. The tumor attachment to the dural surface was excised using micro-scissors in six of our patients. The dural closure was performed using 4-0 non-braided prolene sutures. As a paramedian durotomy was performed, as soon as tagging sutures were released, the dural edges resumed their preoperative position thus requiring only a few sutures for an adequate closure. We admit that a mean follow up of 18 months is insufficient to assess for the development of spinal deformities utilizing this minimally invasive approach.
| » Conclusions|| |
The unilateral hemilaminectomy approach may be considered as the procedure of choice for juxtamedullary spinal tumors. A precise tumor location with the help of a contrast MRI scan obtained in coronal, axial and sagittal planes should always precede the surgical procedure. Use of high-speed drills and avoidance of rongeurs minimizes the chances of spinal cord injury. Tumor debulking (rather than its en-bloc excision) helps in preventing cord damage. This surgical approach is suitable at all spinal levels and is appropriate even when multiple spinal levels are involved.
| » Acknowledgement|| |
Authors acknowledge efforts of Ms Neha, student of MSc (Department of Pharmacology, PGIMER) for providing the diagrammatic representation of the surgical technique in the present manuscript.
| » References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]