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|LETTER TO EDITOR
|Year : 2016 | Volume
| Issue : 6 | Page : 1345-1347
Commentary: Surgery for pure midline ventral spinal intradural lesions
Department of Neurosurgery, King Edward VII Memorial Hospital and Seth Gordhandas Sunderdas Medical College, Mumbai, Maharashtra, India
|Date of Web Publication||11-Nov-2016|
Department of Neurosurgery, King Edward VII Memorial Hospital and Seth Gordhandas Sunderdas Medical College, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Muzumdar D. Commentary: Surgery for pure midline ventral spinal intradural lesions. Neurol India 2016;64:1345-7
Surgery for ventral intradural lesions is formidable. The lesions, which present in the midline ventral location include a neurenteric cyst, arachnoid cyst, meningioma, schwannoma, cavernoma, hemangioblastoma, and rarely, tuberculoma.,,, Most of them are intradural extramedullary in location; however, an intramedullary location is also described. The cervical canal and the cervicothoracic junction are the most common locations. They can be asymptomatic if they are small in size or may present with minimal neurological symptoms and signs. Pain can be a prominent symptom due to meningeal irritation. Intermittent spinal cord compression can occur in cystic lesions due to fluctuations in the size of the cyst following continued secretion of fluid by the columnar epithelium, which often layers the cavity of the cyst. In view of these lesions being benign, complete resection without inflicting any additional neurological deficit is paramount for a successful outcome.,,,,,
The surgical approach is primarily directed by a thorough and detailed study of the sagittal and axial sequences of the magnetic resonance imaging (MRI)., Most of the lesions are present on the posterior or posterolateral aspect of the cord, causing varying degrees of spinal cord compression, displacement, or rotation. In addition, the spinal cord may depict T2-signal intensity changes suggesting an ischemic insult or venous congestion. A review of the literature reveals that surgery via the posterior approach suffices in most instances. In most ventral intradural extramedullary tumors, there is some degree of cord rotation and lateral displacement. A bilateral or unilateral laminectomy provides an adequate exposure.,,,,, There is usually no need to remove the facet or resect the pedicle. However, varying degrees of incremental lateral bone resection, transverse dural incisions, dentate ligament division, and gentle cord rotation provides adequate exposure for safe removal of these tumors. The primary nature of the tumor assumes importance. Only 20% of intradural schwannomas arise from the anterior rootlets. Ventral extension of the tumor for more than two segments is difficult to resect.,, A uniform hyperintense signal on T2-weighted MR images is suggestive of a relatively soft-to-firm tumor consistency. A posterolateral corridor allows access to the tumor. Internal decompression of the tumor or aspiration of the cyst contents reduces tumor size, creates more working space, and enables progressive delivery of the initially nonvisualized tumor into the resection cavity. A well-defined arachnoidal plane usually allows the nonvisualized tumor-spinal cord margin to be developed by feel alone through the gentle use of microdissection techniques. Sometimes, it may allow only partial collapse of the cystic mass and total resection may be accomplished by piecemeal removal of the cyst membrane. Leakage of the cyst contents may result in meningeal irritation. A partial resection is the major cause leading to recurrence of a neurenteric cyst. Direct exposure of the cyst through the anterior approach might ensure total resection without rupturing of the cyst and possibly avoid meningitis. In specially challenging situations, appropriate decisions can be taken depending on the location, size, extension, and pathology of the lesion. Endoscopic-assisted removal of ventral intradural spinal tumors through a posterior approach allows minimal retraction of the spinal cord as well as inspection of the corridors, which are difficult to visualize with the microscope. The primary risks of cervical laminectomy include injury to the spinal cord, dura mater, and the nerve roots.,, Prolonged and excessive retraction of the spinal cord may cause permanent damage. The ventral access via the posterior or posterolateral exposure is further constrained by the vertebral artery and the nerve roots. Root resection for exposure can result in significant morbidity, even with limited dorsal root resection. The risk of instability is greater at these levels because of the need for partial facetectomy. The vascular complications, including vertebral artery injury and venous bleeding, may result in a hematoma. Lateral mass screws require a precise localization to avoid injury to the vertebral artery. At the upper cervical levels, however, care must be taken to identify and protect the spinal accessory nerve. Injury to this nerve can cause cosmetic and functional morbidity of the involved shoulder and arm because of denervation of the trapezius muscle. Minimally invasive approaches to intradural pathology have been recently described. In experienced hands, these exposures have been demonstrated to produce satisfactory outcomes in carefully selected cases. The major risk of morbidity in these cases occurs during the intradural component of the surgery, not the exposure. Spinal stability is rarely compromised by standard posterior approaches.
The anterior approach is suited best for ventral midline intradural tumors, which are small in size, apposed to the ventral surface of the spinal cord and produce no significant displacement or rotation of the spinal cord.,, Although risky, increasing experience with the anterior cervical approach and corpectomy has led to its use in removal of purely ventral midline tumors. The corpectomy provides a relatively wide window to explore the pathology under microscopic magnification. After the total removal of the lesion, a watertight dural closure is mandatory and the cervical spine is stabilized with autologous iliac bone graft, plate, and screws. Ventral lesions at the C3–7 level present greater challenges because the spinal canal is relatively narrow at these levels. A standard anterior supraclavicular approach with or without a manubriumectomy can allow access to lesions extending till T2.
The anterior cervical approach carries risks, such as the injury of nearby structures, failure of fusion and graft displacement, and delayed formation of hematoma and cerebrospinal fluid leakage.,, Although anterior exposure at these levels is more familiar to the surgeon and represents a well established standard trajectory, the approach is time consuming and entails more sustained retraction of the anterior cervical soft tissues. This may increase the risk of postoperative soft tissue complications as well as swallowing and voice deficits. It is difficult to obliterate the dead space with anterior cervical exposures. Cerebrospinal fluid (CSF) leak with the development of an anterior cervical pseudomeningocele can be a problem. In addition to the requirement of a meticulous dural closure, use of a synthetic dural substitute and a temporary continuous spinal drain for 3–5 days may be helpful.,,
Purely ventral thoracic and upper lumbar intramedullary lesions or large extramedullary tumors with significant bilateral tumor components, that are producing significant spinal cord compression without cord rotation or lateral displacement, can present challenges to safe surgical treatment. Posterolateral exposures may not ensure complete excision of tumors unless it is small in size. Division of the thoracic T-2 root could potentially result in Horner's syndrome, and lower thoracic motor root division (T8–L1) may cause painful pseudohernia of the abdominal wall, particularly in middle-aged men.,, A formalized anterior or anterolateral approach to ventral intradural spinal pathology may require an open thoracotomy at the upper and middle thoracic levels and the trans-diaphragmatic exposure at the thoracolumbar junction, which are technically challenging. The large intrapleural dead space that exists at subatmospheric pressure and the requirement of a chest tube drainage present additional risks of postoperative CSF fistula.
Rajagandhi et al., have reported a ventral transcorporeal approach for purely ventral intradural lesions in two patients with a successful outcome. They had no postoperative complications and the patients did not require lumbar CSF drainage during their postoperative course. Although most surgeons would prefer a posterior or far lateral extended posterolateral approach for ventral lesions, it is also fraught with risks of excessive cord manipulation and damage. It requires a special expertise for execution. Pure ventral intradural lesions, as depicted in the manuscript, would be possibly better tackled by an anterior approach. Instability and epidural bleeding are worrisome but can be avoided by experience gathered from the anterior surgery for degenerative cervical disc disease. The advantages and limitations of the approach have been well described.
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