Technological advances in preoperative imaging, 3-dimensional (3-D) reconstruction, intraoperative navigation, and microscopic/endoscopic visualization have allowed the concept of minimally invasive neurosurgery to evolve continuously over the past few decades. New surgical approaches developed by pioneers in the field of minimally invasive neurosurgery provide patients with smaller incisions and alternative treatment options.1-5 These new approaches, however, present challenges to individual surgeons not familiar with these procedures.
The supraorbital keyhole approach, described and refined by van Lindert et al3 and Reisch and Perneczky,6 is one of the most well-known minimally invasive methods to treat anterior skull base lesions. It provides access to the suprasellar area and surrounding structures, which include cranial nerves I through IV, the optic chiasm, and the internal cerebral artery and its main branches.7 Although comparable safety and patient outcomes with a standard microsurgical pterional approach were demonstrated in a large-scale study, limitations and technical challenges remain.8 Specifically, there are frequent debates about applying the current microscopic keyhole approach in deep and narrow surgical corridors as required for aneurysm surgery because of limitations from both restricted instrument manipulation and narrowed visual field. These considerations have led us to examine alternative methods to provide surgeons with better instrument control and wider operative vision.
The purpose of this article is to test potential benefits of surgical robotic technology in minimally invasive neurosurgery. A supraorbital keyhole approach was used as a model to demonstrate accessible anatomic structures for comparison with a microscopic keyhole approach. Furthermore, the feasibility of performing aneurysm surgery in the current robotic setting was evaluated and a newly designed piece of robotic equipment, the EndoWrist One Suction/Irrigator (Intuitive Surgical, Inc, Sunnyvale, California) was tested in the neurosurgical setting.
The da Vinci Surgical System (Intuitive Surgical, Inc) was used for 2 cadaver experiments to simulate operating room constraints and conditions. The robot was aligned 30° relative to the cadaver body and positioned to the right side of the head, as shown in Figure 1. The head was positioned supine with a 10° to 15° extension. A supraorbital craniotomy was performed with a drill, and 0° and 30° upward facing stereoscopic endoscopes were introduced into the keyhole separately to visualize neuroanatomy. A standard brain spatula mounted with self-retaining snake retractors was used to provide endoscope access.
Once the eyebrow incision and craniotomy were completed, the da Vinci Surgical System was used throughout the supraorbital transeyebrow keyhole approach from the opening of the dura to the closure of the dura. The dura was opened parallel to the eyebrow with robotic curved scissors (Figure 2). The right frontal lobe was retracted gently with a standard self-retaining snake retractor to provide space for the approach. The amount of retraction in this cadaver study is similar to that in microscopic keyhole surgery for living patients without significant brain swelling. Cerebrospinal fluid was partially suctioned by the EndoWrist One Suction/Irrigator to allow the brain to relax for a better skull base exposure. A tableside assistant was available throughout the procedure to adjust the retractor and to exchange robotic instruments; the surgeon remained nonsterile at the robot console.
The 0° endoscope provides adequate 3-D visualization of the anterior and middle skull base. The EndoWrist instruments provide maneuverability at their proximal end and were able to angulate around critical parasellar structures while providing satisfactory dexterity to perform the dissection. The robotic suction/irrigator reduces the need for a tableside assistant.
The outer arachnoid membrane surrounding the optic nerve and internal carotid artery was opened by use of standard microscopic dissection techniques. With further dissection, the optic nerve, optic chiasm, carotid artery, and third cranial nerve were visualized. The sylvian fissure was then exposed from the proximal sylvian membrane to the distal M1 segment with Potts scissors and the EndoWrist One Suction/Irrigator (Figure 3).
After opening of the sylvian fissure, a small incision was created on the M1 segment. The ability of the da Vinci Surgical System to suture in a deep, narrow corridor was tested (Figure 4). Three simple stitches were quickly placed to close the incision. In standard microsurgery, achieving this in a deep-seated structure, especially with a small craniotomy, would be a time-consuming procedure.
The sellar region was visualized with the 0° endoscope after opening of the chiasmatic cistern. The EndoWrist instruments were able to reach the prechiamatic space and to perform dissection in the surrounding area. With careful manipulation of the camera and robotic instruments, the pituitary stalk, pituitary gland, tuberculum sella, and contralateral internal carotid artery were identified. After opening the lamina terminalis cistern, we were able to trace the anterior cerebral artery, approaching the junction of the A1 and A2 segments in addition to the recurrent artery (Figure 5).
The oculomotor nerve was identified after gentle retraction of the temporal lobe. The origin of the posterior communication artery from the internal carotid artery and the nearby anterior choroidal artery were easily visualized. We also attempted to apply an aneurysm clip with the existing robotic tools, although such instruments could not generate the required force for clip placement. A manual clip applier was used. An articulating clip applier would provide much benefit over traditional straight tools, providing additional dexterity to allow surgeons to optimize the angle of clip placement (Figure 6).
The barriers of the current microscopic supraorbital keyhole approach to the skull base lie in the deep-seated anatomic structures and narrow surgical corridors. In other words, limitations in obtaining a sufficient visual field and restrictions in instrument maneuverability prohibit this approach from being widely accepted8 (Figure 7). These hurdles also restrict a surgeon from carrying out this dissection safely. Although some surgeons use endoscope-assisted technology to overcome the visual field limitation in the keyhole approach, 9,10 the 2-dimensional visualization can make this approach even more difficult for a neurosurgeon unfamiliar with the technique. Moreover, the security and reliability of the endoscope fixation device can be another challenging issue.
The benefits of surgical robots have been demonstrated in various specialties, eg, urology, obstetrics, orthopedics, cardiac surgery, and gynecology.11-14 The advantages of robotic surgery include high-definition 3-D stereoscopic visualization, better control with increased accuracy and reduced tremor, and a high range of instrument motion even in constrained spaces such as deep, narrow corridors.15-17 These benefits may help us solve the obstacles frequently encountered during keyhole skull base surgery. A few groups have described the designs of and preclinical and clinical results from neurosurgery-specific robots,18-21 but none has succeeded commercially. The Neuromate has been used for stereotactic brainstem biopsies,22 and the ROBOCAST project has focused on improving trajectories for keyhole biopsy and drug delivery.21 In terms of brain tumor removal, an atypical meningioma has been partially removed by the NeuRobot, a telecontrolled microsurgery device consisting of 3 arms and an endoscope. 19,23,24 Morita et al18 developed a robotic system for accessing areas in the deep brain. Sutherland’s Neuroarm was the first neurosurgical robot to take advantage of image guidance provided by magnetic resonance imaging.25 Concerns and debates regarding safety and practicality have been argued from different neurosurgeons’ viewpoints for all of these platforms.23,26
The da Vinci Surgical System provides surgeons with high-definition 3-D visualization through 8.5- or 12-mm-diameter endoscopes. When combined with the robotic arm, it provides a stable and reliable imaging platform, the image quality of which rivals that of a microscope with a broader visual field.
In general, the da Vinci Surgical System has seen widespread adoption in complex procedures that require increased dexterity because the EndoWrist instruments allow manipulations to take place in confined workspaces. This is particularly well suited to the narrow corridor of keyhole surgery in that robotic instruments provide 7° of freedom and 90° of articulation, which are superior to the 4° of freedom and 0° of articulation of standard keyhole instruments.27 In addition, the robot provides a tremor-filtering function that is able to eliminate even small-scale tremors of surgeons.26 In the field of neurosurgery, the da Vinci Surgical System has been used in odontoidectomy, paraspinal schwannoma resection, anterior lumbar interbody fusion, and intrauterine myelomeningocele repair.28-32
In this study, we demonstrate the feasibility of applying robotic technology to minimally invasive skull base neurosurgery via the supraorbital keyhole approach. With the advantages of the robotic system, this approach provides a wide exposure and accessibility to the skull base structures (Table). Recently introduced instruments may expand the utility of robotic keyhole surgery to include skull base tumors like meningiomas and craniopharyngiomas located at the anterior and middle skull base.
Vascular surgery may be another potential application of this robotic approach, given that the internal carotid artery, posterior communicating artery, anterior choroidal artery, anterior cerebral artery, anterior communicating artery, Heubner artery, middle cerebral artery, and middle cerebral artery bifurcation are easily exposed by this method. The robotic system provides neurosurgeons with tremor-free, highly maneuverable and precise tools, reducing the fatigue that a neurosurgeon may suffer by maintaining stable and delicate hand movements during lengthy microsurgical procedures.33,34 Although a proper robotic instrument for aneurysm surgery is not currently available, an articulating clip applier would provide neurosurgeons additional dexterity in adjusting the exact angle of clip placement.
Despite the advantages provided by robotic keyhole surgery, there are some drawbacks to using the da Vinci Surgical System in supraorbital keyhole surgery. First, the lack of a proper bone-cutting tool on the da Vinci Surgical System means that a high-speed drill is needed to perform the keyhole craniotomy. The da Vinci Surgical System is moved into place after the craniotomy. An appropriate bone-cutting tool may eliminate the inconvenience of docking the robot after the surgical procedure has begun. Second, an improper position of the robotic arms may increase the risk of arm collisions, which could interrupt the surgical procedure. Experience with and training on how the robotic system works would be necessary to reduce the chances of robotic arm collisions. Third, the da Vinci Surgical System represents a large capital investment on the part of a hospital. No data available are to evaluate the cost-to-benefit ratio of this kind of investment in neurosurgery, and it currently is difficult to evaluate the cost-effectiveness. For the hospitals that already have this system, however, a neurosurgical application may increase the use of their preexisting investment and help defray cost. Finally, bleeding control and visualization in a setting with blood, not addressed in this cadaver study, could be a challenging issue during a live procedure. Although the limitations of the cadaver model prevent actual testing of this hypothesis, the current robotic bipolar instrument and newly developed suction/irrigator tool should provide an appropriate solution.
We demonstrate the feasibility of using a da Vinci Surgical System to perform a minimally invasive supraorbital keyhole surgery in cadaver models. This system enables neurosurgeons to dissect and suture in a deep-seated surgical field with broader vision and dexterity with articulable instruments. Vascular surgery is another potential application if an appropriate clip applier is developed. Further evaluations in both cadaver and clinical studies are necessary to better assess the safety issues and benefits of using the da Vinci Surgical System in supraorbital keyhole surgery.
While demonstrated in a cadaver model, the procedure nonetheless represents an unlabeled use of the da Vinci Surgical System. Dr Sorger is an employee and stockholder of Intuitive Surgical. The other authors have no personal financial or institutional interest in any of the drugs, materials, or devices described in this article.
We thank Intuitive Surgical, Inc, for technical and equipment support.
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