Posterior Approach for a Ventral Intradural Extramedullary Meningioma: 2-Dimensional Operative Video

Ventral thoracic meningiomas are rare entities in which the spinal cord is attenuated and draped over the meningioma symmetrically. This is a challenging surgical entity compared to typical intradural meningiomas, which nearly always eccentrically displace the cord. In these more common meningiomas, surgical access is fairly straightforward as the meningioma is often visualized upon opening the meninges. Resection can be more safely performed with the cord largely shifted. In cases of ventral meningioma, the tumor is hidden ventral to the spinal cord, and techniques to safely mobilize the spinal cord must be utilized. We demonstrate that an entirely posterior approach allows complete resection of a ventrally situated mass. After careful identification and sectioning of the dentate ligament at multiple levels on the right side of the canal, we then suture and rotate the dentate ligament at each site, thereby allowing progressive visualization of the ventral meningioma. A narrow, but viable, working corridor to the tumor allows safe debulking. Once it is felt that the tumor can no longer be safely excised through the created corridor, we then disconnect our dentate sutures and move to the other side of the canal. Similarly, the dentate is sectioned and sutured so that the contralateral aspect of the meningioma can be visualized and debulked. The tumor can then be safely removed. A standard posterior approach and midline durotomy allows this bilateral approach to a ventrally situated meningioma and, therefore, in our mind, represents a safe and also highly effective road to resection. Patient consent was obtained prior to publication.

Far Lateral Approach for Resection of Transverse Ligament Cyst

Objectives This study was aimed to describe a far lateral approach for microsurgical resection of a transverse ligament cyst, with emphasis on the microsurgical anatomy and technique. Design A far lateral craniotomy is performed in the lateral decubitus position. After opening the dura laterally, dural sutures are placed for retraction. A stitch placed through the dentate ligament is advantageous to rotate the spinal cord to allow access to the ventral cyst. The cyst is marsupirlized and mass effect on the spinal cord is relieved. Photographs of the region are borrowed from Dr Rhoton's laboratory to illustrate the microsurgical anatomy. Participants The first author performed the surgery and edited the video. Chart review and literature review were performed by the other authors. Outcome Measures Outcome was assessed with postoperative neurological function. Results The patient was discharged home after an uneventful hospital course. At short-term follow-up, the patient had a significant improvement in postoperative strength. Conclusion The far lateral approach provides an adequate corridor to the ventrolateral brainstem in combination with utilization of the dentate ligament to reach ventral cysts compressing the spinal cord. An adequate understanding of the relevant microsurgical anatomy is a key to safe surgery in this region.The link to the video can be found at: https://youtu.be/5MGVPO2Q2pI.

Spinal Cord Suspension Using Dentate Ligament Hitch Stitches: A Novel Technique for the Repair of Ventral Spinal Cord Herniation

BACKGROUND Idiopathic spinal cord herniation is usually repaired by releasing the spinal cord and inserting a dural patch to close the herniated segment of dura. However, reherniation is a potential limitation of this standard technique. OBJECTIVE To describe early results of a novel technique that utilizes the dentate ligament to hitch the spinal cord and prevent reherniation. METHODS Two patients underwent dural hernia repair and the dentate hitch technique was performed. RESULTS Restored lower limb power and mobility, and satisfactory reduction of spinal cord herniation on magnetic resonance imaging in 2 patients at 6- and 24-mo follow-ups, respectively. CONCLUSION The dentate hitch technique can achieve repair of spinal cord herniation, with satisfactory postoperative results and minimizes the risk of reherniation.

Surgical management of ventral intradural spinal lesions

Object Access to the ventral intradural spinal canal may be required for treatment of a variety of lesions affecting the spinal cord and adjacent intradural structures. Adequate exposure is usually achieved through a standard posterior laminectomy or posterolateral approaches, although formal anterior approaches are used to access lesions in the subaxial cervical spine. Modifications of the standard posterior exposure as well as ventral or ventrolateral approaches are increasingly being used for treating intradural spinal pathologies. In this study, the authors review their experience with 35 consecutive cases of ventral intradural spinal lesions. Methods Only patients with intradural lesions located completely ventral to the dentate ligament attachments were included in this retrospective study. Patients with the following lesions were excluded from the study: lesions at the level of the filum terminale/cauda equina, lesions with any component that extended dorsally to the dentate ligament, or lesions with extradural extension (that is, dumbbell tumors) below the C-2 level. Between January 2000 and September 2009, a total of 35 patients (age range 17–72 years, mean 42.6 years) with ventral intradural spinal pathology underwent surgery at the authors' institution. Results There were 28 intradural extramedullary mass lesions: 15 meningiomas, 12 solitary schwannomas, and 1 neuroenteric cyst. Surgical approaches to these lesions included 23 posterior or posterolateral approaches, 4 anterior approaches with corpectomy followed by tumor resection and reconstruction, and 1 lateral transforaminal resection. No patient had evidence of instability at follow-up, which ranged from 6 months to 8 years in duration. One patient had worsened spinal cord function following surgery. There were 7 patients with intramedullary lesions: 2 hemangioblastomas, 2 cavernous malformations, 2 perimedullary fistulas, and 1 astrocytoma. All but 1 were superficial pia-based lesions arising ventral to the dentate ligament. Five of the 6 pia-based lesions were successfully resected via a standard posterior laminectomy, partial facetectomy with dentate section, and spinal cord rotation. One midline pial lesion was successfully removed with a minimally invasive retropleural thoracotomy. The astrocytoma was resected through an anterior cervical corpectomy, which was followed by instrumented reconstruction. There were no significant complications or neurological morbidity at follow-up (range 9 months–6 years). Conclusions Most intradural spinal lesions can be treated with contemporary microsurgical techniques with long-term control or cure of the lesion and preservation of neurological function. Standard posterior approaches provide adequate exposure to safely remove the vast majority of these lesions without the need for a potentially destabilizing resection of the facet or pedicle. Posterior exposures with varying degrees of lateral bone resection, dentate ligament division, and gentle cord rotation may also provide adequate exposure for safe removal of nonmidline ventrolateral superficial pial presenting spinal cord lesions. Nevertheless, in certain cases of ventral intradural lesions, anterior approaches are necessary and should be considered under appropriate circumstances.

Endoscopic-guided percutaneous radiofrequency cordotomy

The authors present the first clinical implementation of an endoscopic-assisted percutaneous anterolateral radiofrequency cordotomy. The aim of this article is to demonstrate the intradural endoscopic visualization of the cervical spinal cord via a percutaneous approach to refine the spinal target for anterolateral cordotomy, avoiding undesired trauma to the spinal tissue or injury to blood vessels. Initially, a lateral puncture of the spinal canal in the C1–2 interspace is performed, guided by fluoroscopy. As soon as CSF is reached by the guide cannula (17-gauge needle), the endoscope can be inserted for visualization of the spinal cord and its surrounding structures. The endoscopic visualization provided clear identification of the pial surface of the spinal cord, arachnoid membrane, dentate ligament, dorsal and ventral root entry zone, and blood vessels. The target for electrode insertion into the spinal cord was determined to be the midpoint from the dentate ligament and the ventral root entry zone. The endoscopic guidance shortened the fluoroscopy usage time and no intrathecal contrast administration was needed. Cordotomy was performed by a standard radiofrequency method after refining of the neurophysiological target. Satisfactory analgesia was provided by the procedure with no additional complications or CSF leak. The initial use of this technique suggests that a percutaneous endoscopic procedure may be useful for particular manipulation of the spinal cord, possibly adding a degree of safety to the procedure and improving its effectiveness.

Intradural microanatomy of the nerve roots S1–S5 at their origin from the conus medullaris

Object The conus medullaris and the nerve roots from S-1 to S-5 regulate bladder function as well as movement and sensation of the lower extremities. This most caudal region of the spinal cord has not been studied in great detail anatomically despite its important regulatory role. The goal of this analysis is to characterize the normal intradural microanatomy of the sacral nerve roots at their origin from the conus medullaris. Methods The thecal sacs from 20 cadavers were fixated in formaldehyde and dissected under the operative microscope. Results More than 50 rootlets originated from the conus medullaris over a distance of < 3 cm. The rootlets were loosely organized into bundles by the arachnoid membrane with decreasing diameters. These diameters were 1.7 mm (ventral)/2.4 mm (dorsal) at S-1, and 0.17 mm (ventral)/0.4 mm (dorsal) at S-5. The roots were separated by neither the dentate ligament nor interradicular gaps. The number of rootlets decreased in the rostrocaudal direction with 2 ventral and 5 dorsal rootlets at S-1, but only 1 ventral (inconsistently found) and 2 dorsal rootlets at S-5. Typically, 1 nerve anastomosis was present between adjacent dorsal roots from S-1 to S-4. Nerve anastomoses between ventral roots or rootlets of the same root were less frequent. The dorsal segment of origin (linea radicularis) decreased in length from 7.2 mm at S-1 to 4.8 mm at S-5. Conclusions The current study provides anatomical details and specific morphometric data of the intradural contents at the level of the conus medullaris. This information is valuable for intraoperative orientation, endoscopic navigation, and possible intradural nerve stimulation.

Exposure of the vertebrobasilar artery junction with traction of the dentate ligament for the treatment of large vertebral artery aneurysms

✓ A technique for exposing the vertebrobasilar junction with traction of the dentate ligament is described for treatment of large vertebral artery (VA) aneurysms via the far lateral suboccipital approach with partial condylar resection. The most rostral attachment of the dentate ligament is divided above the site where the VA pierces the dura mater. A traction suture is placed into the dentate ligament and gently retracted using mosquito forceps. As a result, the medulla oblongata is lifted dorsally and slightly rotated by the divided and retracted dentate ligament, allowing an approach from a more superior or inferior direction. The present technique is useful for the treatment of large thrombosed VA aneurysms.

Anterior Corpectomy Approach for Removal of a Cervical Intradural Schwannoma

Spinal schwannomas are typically intradural-extramedullary neoplasms thought to arise from Schwann cells or their progenitors which occur proportionally throughout the spinal canal. They most typically arise from dorsal sensory rootlets and occupy a posterior-lateral location in the spinal canal. Thus, posterior surgical procedures have become the conventional method to remove these tumors providing adequate exposure in most cases. More anteriorly located tumors may be approached through a posterolateral direction with section of the dentate ligament and gentle rotation of the spinal cord. However, posterior and posterolateral approaches may be problematic for removing tumors located in the midline and ventral to the spinal cord.Although the anterior approach has been applied widely to treat cervical spondylosis, it has rarely been used to remove intradural tumors. Here, we present a case of a ventral cervical spinal schwannoma removed through an anterior approach followed by spinal reconstruction.