Exploring Unilateral Biportal Endoscopy for Lumbar Intradural Lesions: A Technical and Video Report on Benefits and Key Considerations
Article information
Abstract
Lumbar Intradural extramedullary schwannomas often cause neurological symptoms, and complete surgical removal is mandatory. Traditional surgical procedures for tumor removal have numerous disadvantages, including extensive muscle dissection, prolonged recovery, and increased postoperative pain. As endoscopic surgery becomes increasingly popular for treating spinal disorders, the use of endoscopic techniques for treating spinal tumors is imminent. However, the development of these techniques has been challenging due to various inherent difficulties with traditional endoscopic surgery, including a steep learning curve, technical complexity, and fluid management. In this article, we present a successful case of treating an intradural extramedullary schwannoma using unilateral biportal endoscopy (UBE), share the 2-hand technique involved, and discuss the advantages and limitations of UBE in such cases.
INTRODUCTION
Unilateral biportal endoscopy (UBE) has become a significant trend in contemporary spinal surgery. Compared to traditional spine surgery, UBE not only alleviating pain and restoring functional ability but also promotes enhanced recovery after surgery. Over the past 10 years, UBE has emerged as a promising alternative to conventional surgical methods. However, the UBE technique is currently primarily reported for lumbar discectomy and decompression surgeries, and it is rarely used for intradural pathologies [1]. To date, there have been few reports of using endoscopic assistance to resect intradural lesions [2,3], and even fewer reports of full-endoscopy resection [4-6].
Schwannomas are benign nerve sheath tumors that typically arise from Schwann cells and are often located in the spinal intradural extramedullary space. These tumors, while generally non-malignant, can cause significant morbidity due to their location and the potential for neurological deficits [7].
Traditional surgical approaches to schwannoma resection involve open surgery, which, although effective, is associated with considerable morbidity, including extensive muscle dissection, prolonged recovery times, and increased postoperative pain. In contrast, minimally invasive techniques, such as UBE, offers numerous advantages, including reduced soft tissue damage, decreased blood loss, minimized damage to the epidural blood supply and subsequent epidural fibrosis, shorter hospital stays, and a quicker return to work [8-10].
To the best of our knowledge, there have been no case reports to date of using UBE for the resection of lumbar intradural extramedullary schwannomas. This report aims to provide a comprehensive overview of the technique and skill involved in using UBE for lumbar intradural extramedullary schwannoma resection. It will discuss the surgical procedure, technical considerations, outcomes, and potential complications, drawing on existing literature and clinical experiences to underscore the benefits and challenges associated with this innovative approach.
CASE PRESENTATION
1. History and Examination
A 63-year-old male presented to Daejeon Woori Spine Hospital with the complaint of low back pain radiating to both legs, persisting for a year and worsening over the past month. His preoperative neurologic examination was unremarkable.
2. Imaging Studies
Preoperative magnetic resonance imaging (MRI) of the lumbar spine revealed a 1.6-cm intradural extramedullary mass located in the central canal at the L3–4 level, with a left-side deviation (Figure 1).
Sagittal (A) and axial view (B) of preoperative magnetic resonance imaging, showing a well-defined, homogeneous intradural tumor measuring about 1.6 cm at the L3–4 disc level (arrow).
3. Surgery
The surgical plan involved using the UBE technique to excise the tumor through 2 small skin incisions measuring 2 cm and 7 mm (Supplementary video clip 1). Under general anesthesia, the patient was put in prone position on a radiolucent operating table. The patient’s systolic blood pressure was controlled between 90–100 mmHg with anesthetic drugs to reduce intraoperative bleeding.
The operation was conducted in 3 steps:
Step 1: Exposing the dura with UBE laminotomy.
Step 2: Opening the dura and carefully excising the tumor.
Step 3: Closing the dura and concluding the operation.
Step 1. A puncture needle was placed at the level of upper one-third of the left L4 pedicle on the medial pedicle line under the guidance of fluoroscopy. Two milliliters of Methylene blue was injected via the needle. Then a 2-cm transverse skin incision was made centered on the puncture wound to serve as the work portal. Another 0.7-cm transverse skin incision was made 3 cm above the working portal to function as the scope portal. Serial dilators were used to dilate the back muscle and create a tunnel for the scope and work portals. A 0° endoscope connected to the natural gravity irrigation system (about 60–90 cm above the surgical surface) was inserted via the scope portal. Triangulation of scope and instrument was done on the L3 spinolamina junction. Muscles were removed from the interlaminar space using an endoscopic shaver drill (Stryker Corp., Kalamazoo, MI, USA). Arthrocare bipolar (Smith & Nephew, Watford, England) was then used to control bleeding and clean up the residual soft tissues. Drilling L3 lamina cranially from interlaminar space using endoscopic shaver drill until reveal the central gap of ligamentum flavum. Contralateral sublaminar bone drilling above the ligamentum flavum to expose the midline of the dura sac and gain more working space. Ipsilateral drilling of left L3 inferior articular process to expose left L4 laminar and superior articular process (SAP), detach the left border of ligamentum flavum from L4 lamina and SAP with Kerrison punch and curette. Remove the whole ligamentum flavum in one piece and complete laminotomy.
Step 2. Dura incision was made 1mm apart from the midline of the caudal side dura with microknife. Then dura hook was inserted into the dura incision and extend it cranially. The Hopper cannula (Medirover, Hanam, Korea) was inserted via scope portal between the gap of dura matter in order to spread open and gain surgical view. The arachnoid membrane was carefully dissected with dura hook. By slightly spreading the dorsal nerve roots, the tumor was visualized. The tumor was moderately vascularized, yellowish, soft consistent with mild adhesion to adjacent rootlets. Carefully dissect the adhesion between the tumor and nerve roots by dissector and Hopper cannula using 2 hand technique. During this step, by adjusting the height of the saline bag and the condition of outflow to set the water pressure at an appropriate level, the nerve roots are prevented from protruding from the dura mater. After the tumor removed, hemostasis was done with bipolar coagulation.
Step 3. A thin piece of gelfoam was placed into subdural space to prevent nerve root bulging out during the dura closure. Use Anastoclip (Lemaitre, Burlington, MA, USA) to align the cut edges of the dura and suture them together with approximately 1mm intervals. Temporary stop the irrigation to confirm there were no active bleeding and leakage of cerebrospinal fluid. A drain was placed in epidural space. The skin wounds were sutured by 3-0 nylone. The blood loss was minimal, and the operation time was 60 minutes.
4. Postoperative
After the operation, the patient had a dramatically improved of pain in bilateral lower limbs. His back visual analogue scale (VAS) decreased from 4 to 2, and leg VAS decreased from 6 to 2 immediately after operation (Figure 2). Drain was removed on postoperation day (POD) 2. Postoperative computed tomography confirmed bilateral facet preservation (Figure 3).
Line chart presenting the back and leg visual analogue scale (VAS) score at 3 different time point, representing preoperative, postoperative day 1 (POD1) and 1-month follow-up (POD30).
Postoperative 3-dimensional computed tomography, showing unilateral laminotomy of L3 for tumor removal (arrow), and the preservation of the left L3–4 facet joint (circle).
The 1-month postoperative MRI showed total removal of the tumor, with no sign of cerebrospinal fluid leakage. Ambulation was start on POD 3, and discharge was arranged on POD 10.
During outpatient department follow-up at 1 month, the patient remain symptom free and MRI showed no evidence of residual tumor (Figure 4).
Sagittal (A) and axial (B) T2-weighted magnetic resonance imaging at the 1-month follow-up, showing total removal of the tumor.
A 63-year-old male presented to Daejeon Woori Spine Hospital with the complaint of low back pain radiating to both legs, persisting for a year and worsening over the past month. His preoperative neurologic examination was unremarkable.Written consent for publication has been obtained from the patient.
DISCUSSION
Full endoscopic spinal surgery has emerged as a leading trend in the treatment of spinal diseases in recent years. This minimally invasive technique offers significant advantages over traditional open surgery, including reduced tissue damage, quicker recovery times, and less postoperative pain [8-10]. However, despite these benefits, the application of full endoscopic techniques to lumbar intradural lesions remains particularly challenging.
One of the primary challenges in endoscopic surgery for intradural lesions is the restricted working corridor. The endoscopic equipment provides a confined space, which significantly limits the surgeon's ability to maneuver instruments. This constraint makes precise dissections and manipulations difficult, especially when dealing with complex intradural pathologies, such as large or highly vascular tumor. According to Zhu et al. [11], this limitation can hinder the complete removal of tumors and increase the risk of surgical complications. In our case, the use of UBE and the 2-hand technique can slightly improve the aforementioned issues. Firstly, compared to uni-portal endoscopy, UBE has an independent working portal that enhances surgical flexibility [12]. Furthermore, the procedure can be performed using conventional instruments, which means there are more tools available during tumor dissection and dura closing. Secondly, with the help of a Hopper cannula on the endoscope, the 2-hand technique can be implemented. During the tumor dissection stage, the Hopper cannula held in the left hand can be used to hold the tissue and create tension, while the instrument in the right hand, such as a tumor forceps or dissector, can be used to separate the tissue. In cases requiring sharp dissection, the working portal allows for the easy insertion of microscissors. In our case, the tumor was completely excised using blunt dissection, so sharp dissection was not necessary. However, it is certainly feasible if needed.
Another significant challenge during full endoscopy is the management intraoperative bleeding. Tumors are often highly vascularized tissues, which tend to bleed easily during resection. Due to the narrow field of view and confined working space of endoscopy, achieving hemostasis is always challenging, and in the most severe cases, it can even prevent the continuation of the surgery, as highlighted by Parihar et al. [3]. Using UBE surgery for hemostasis offers the following advantages. First, the UBE system has separate inflow and outflow channels, which ensures that bleeding within the surgical field does not obscure the surgeon's view but is directed away from it. This feature makes the hemostatic demands of UBE surgery inherently lower. Second, in addition to using radiofrequency bipolar for hemostasis, UBE surgery can also employ traditional hemostatic techniques for challenging bleeding, such as the use of bone wax and Gelfoam.
Regarding UBE, a water-based surgical technique, the primary concern when using it for intradural operations is whether the water pressure will enter the intradural space, subsequently increasing intracranial pressure (IICP). In our UBE surgeries, a natural gravity irrigation system positioned approximately 60-90 cm above the surgical surface was used. This setup technically provides a pressure of 60-90 cmH2O in the surgical chamber, which is higher than the normal intracranial pressure (ICP) in adults, which ranges from 13-20 cmH2O. Our technique addresses this issue in 2 ways. Firstly, in the context of UBE, maintaining effective outflow is essential. The pressure within the surgical chamber is influenced by the height difference between the saline bag and the chamber, but more importantly, by the resistance in the outflow. With no outflow resistance, the pressure corresponds to the height from the chamber to the surface wound, potentially reducing the risk of excessive pressure within the intradural space. For instance, if the saline bag is positioned 70 cm above the patient's lumbar region and the outflow is completely obstructed, the pressure in the chamber would be 70 cmH2O. Conversely, if the outflow is completely unobstructed, the pressure in the chamber would be the distance from the chamber to the skin opening, i.e., 5 cmH2O. This fluid dynamics principle highlights the importance of maintaining outflow during water-based intradural surgery (Figure 5).
Numerical values of the water pressure in the surgical chamber under conditions of good outflow (A) and blocked outflow (B).
Secondly, intraoperative monitoring of nerve root movements provides real-time feedback on intracavitary pressure. When the pressure inside the chamber is lower than the patient's intracranial pressure (ICP), nerve roots tend to float outward. Conversely, if the water pressure exceeds the ICP significantly, the nerve roots are pushed towards the ventral dural side. This visual cue is a critical indicator for surgeons to adjust irrigation flow and pressure accordingly (Figures 6 and 7).
The condition of the root under conditions of low (A), medium (B), and high surgical chamber pressure (C), respectively. (A) When the chamber's hydrostatic pressure is lower than the patient's intracranial pressure (ICP), the root tends to bulge out of the dural opening. (B) Good hydrostatic pressure control maintains the chamber's hydrostatic pressure at a level comparable to the patient's ICP. (C) When a large hydrostatic pressure is infused into the dura, it compresses the root towards the opposite side, posing a risk of increased ICP.
The different conditions of the root under varying water pressures. (A) The hydrostatic pressure in the surgical cavity is greater than the patient's intracranial pressure (ICP), with the root not protruding from the dura and the arachnoid membrane clearly indented. (B) The root protruding beyond the dura, indicating that the ICP is higher than the water pressure inside the surgical cavity.
A study on the water dynamics in UBE indicated that maintaining water pressure between 4.41 cmH2O and 31.00 cmH2O is optimal [13]. This suggests that effective outflow management can help keep the intradural pressure within safe limits, thus preventing IICP. The free-hand manipulation facilitated by UBE also contributes to better surgical outcomes by allowing more precise control over the irrigation and suction mechanisms. Finally, while this technique helps prevent intraoperative IICP, it is not yet perfected. The best prevention can be achieved with real-time monitoring using an intraoperative ICP monitor.
One major obstacle to using endoscopic surgery for intradural lesions is the difficulty of dural repair. Traditionally, suturing the dura in the confined surgical space is challenging and requires high skill. In our case, we demonstrated the use of Anastoclip for dural repair, which was both quick and secure. Postoperative MRI showed no evidence of cerebrospinal fluid leakage, confirming the effectiveness of Anastoclip dural closure (Figure 8). However, this technique has limitations; in elderly patients with very thin dura, Anastoclip may fail to close the dura and could cause further damage. Therefore, the development of endoscopy-specific dural suturing devices is needed to overcome this issue and improve the adoption and effectiveness of these surgical procedures.
(A) An axial view of postoperative computed tomography, showing the Anastoclip used for dural closure (arrow). (B) A photograph showing the completion of dura suturing in the operative view.
The learning curve for endoscopic techniques, especially for intradural lesions, is notably steep. Lewandrowski et al. [14] highlighted the technical difficulties and the high level of proficiency required for these procedures. They observed that while outcomes can match those of traditional surgery when performed by experienced surgeons, the overall complication rates are higher. This underscores the necessity for extensive training and experience to achieve successful outcomes, potentially limiting the widespread adoption of these techniques. We recommend that surgeons attempting to use UBE for intradural tumor removal should ideally have experience with at least 20 cases of open surgery for intradural extramedullary tumor removal, as well as 500 cases of UBE-unilateral laminotomy bilateral decompression procedures and 50 cases of cervical and thoracic decompression surgeries. Moreover, it is important to be mentally prepared to convert to open surgery if necessary.
The microsurgical technique remains the standard for the removal of intradural tumors. From our experience, small to medium-sized intradural lesions that do not extend into the foramen can be approached endoscopically. However, larger lesions, those with significant adhesion to critical structures, or those located in more challenging areas, such as dumbbell tumors, are not suitable for endoscopic techniques. The general cutoff size is around 2–3 cm, depending on the location and extent of adhesion. Even so, there is a pressing need for the development of more sophisticated endoscopic tools tailored to the challenges of intradural surgery. Tools that offer greater flexibility, improved hemostasis, and enhanced visualization capabilities could significantly improve the safety and efficacy of these procedures. The integration of such tools, along with enhanced imaging techniques, could help overcome many of the current limitations.
CONCLUSION
Using UBE for lumbar intradural extramedullary tumor resection extends the application of minimally invasive endoscopic techniques while addressing some inherent challenges and limitations of traditional endoscopic surgery. In this article, we demonstrate the feasibility of UBE in treating lumbar intradural lesions through a technical note and a video report. Additionally, we emphasize the importance of managing water pressure in the surgical chamber during the operation. Continued development of specialized tools and advanced imaging techniques will be essential to overcoming current limitations and improving patient outcomes.
Supplementary Material
The Supplementary video clip 1 for this article is available at https://doi.org/10.21182/jmisst.2024.01466.
Supplementary video clip
Notes
Conflict of Interest
The authors have nothing to disclose.
Funding/Support
This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.