An overview of endoscopy in neurologic surgery
ABSTRACT
Endoscopy allows neurosurgeons to reach regions in the brain and spine through minimally invasive approaches. Such areas were previously accessible only by extensive and invasive approaches that limited the ability to see the areas of interest. Physicians are increasingly caring for patients who have undergone these procedures (eg, for pituitary tumors, hydrocephalus, and other intracranial, peripheral nerve, and spinal problems). This article familiarizes nonneurosurgeons with these techniques.
KEY POINTS
- An increasing number of neurosurgical patients are undergoing endoscopic surgeries of the brain, spine, and peripheral nerves. Familiarization with these techniques provides medical specialists with important knowledge regarding appropriate patient care.
- The combination of classic microscopic and endoscopic procedures improves surgical outcomes by increasing surgical maneuverability and reducing manipulation of eloquent structures.
- Further innovations in optical physics, electronics, and robotics will dramatically improve the potential of endoscopic neurosurgery in the next decades.
FURTHER DEVELOPMENTS
Multivariable rigid endoscopes like the EndoCAMeleon (Karl Storz, Tuttlingen, Germany) or the EndActive (Karl Storz, Tuttlingen, Germany) for cerebellopontine angle surgery represent a starting point to overcome some of the aforementioned limitations.31,32 They are inserted in the surgical field with a direct 0° angulation view into the operative site beyond neurovascular structures that need to be preserved and that obstruct the microscopic view. Once the final position is reached, the field of view is directed toward the region of interest without moving the endoscope tip.
The EndoCAMeleon is a rigid rod-lens endoscope, steerable in one plane from –10° to +120° by a fine optomechanical mechanism. Anatomic laboratory testing found it to be superior in terms of usability and visualization compared with rigid fixed-angle endoscopes.31 The first clinical experiences have been promising; however, ergonomics and the limited perspective of a single plane of rotation leave room for improvement.
The EndActive endoscope might overcome such limitations.33 This device is a rigid videoendoscope connected to a laptop (video data) and USB port (control and power supply); thus, it weighs less and can be held in one hand like a microsurgical instrument. The endoscopic imaging system allows the operator to simultaneously see a 160° wide-angle view of the site and an inset of a specific region of interest. The surgeon can hold the device like a microsurgical instrument in one hand and control movements precisely due to its reduced weight and ergonomic shape.
,The multiplanar variable-view rigid endoscope has proven to be useful for working on diverse anatomic structures such as intracranial vessels and cranial nerves. The device is effective in narrow working spaces where even small movements can jeopardize the delicate surrounding structures. The multiplanar variable-viewing mechanism in a compact device offers advantages in terms of safety and ergonomics. Improving the usability will probably optimize the applicability of those endoscopic devices in neurosurgery. A major drawback of the current prototype is poor image resolution, which will probably soon be overcome with the ongoing progress in electronic microchip technology.
The addition of laser technology to endoscopic techniques offers a huge potential to neurosurgery but has achieved little acceptance to date. The reasons include concern regarding heat production, uncontrollable and distant penetration, and tissue interaction. Experiences with a 2-micron continuous- wave laser (RevoLix Jr, LISA Laser Products, Katlenburg-Lindau, Germany) for neuroendoscopic intraventricular procedures proved this laser to be a valuable and useful tool with safe applicability for endoscopic intracranial procedures in patients of all ages.34
Parallel to the launch of video screens for other uses with higher image definition, the image quality on the 2D endoscope cameras has been constantly improving over the last years. At the same time, the introduction of modern 3D endoscopic monitors is promising. However, 3D endoscopes have some disadvantages compared with the 2D endoscopes. First, the smallest 3D endoscopes are 4 mm in diameter, compared with 2.7 mm for 2D endoscopes. Moreover, the field of view with the 3D endoscope is less than half of that with conventional 2D endoscopes.34 When working in and around a region with critical neurovascular structures in close proximity, this loss of field of view can result in an increase in iatrogenic injury from the endoscope. In addition, 3D endoscopes require special glasses, generating a potential obstacle to the seamless integration of visual information from the microscope and endoscope. Finally, some surgeons experience vertigo when looking at the 3D picture through the glasses, which limits its universal applicability.
CONCLUSIONS
Using the endoscope and microscope as complementary and not competing tools allows surgeons to benefit from both technologies at the same time.35,36 The intraoperative combination of these 2 powerful visualization tools expands the effectiveness of microsurgical procedures and has the potential to further improve surgical results and reduce surgical risks. With endoscope-assisted microsurgery, visualization is often far superior to surgical maneuverability.
Endoscopic neurosurgery will likely be influenced by further innovations in optical physics, electronics, and robotics. Specific implementations in endoscopic systems are likely to pave the way for remarkable progress in minimally invasive surgery, such as robotic surgical technology, further miniaturization of devices, improvements in 3D endoscopy, multiport endoscopy, and new designs for surgical instruments. Future progress in flexible endoscopes and wireless capsule or camera technology may reduce our dependence on rigid rod lens systems. Rigid variable-view endoscopes will bring endoscopes closer to ideal attributes utilizing newer instrumentation that is tailored to specific indications and techniques.37,38 Extension of the visual field by the feature of a movable optic lens may allow the neurosurgeon to use tailored keyhole approaches to treat pathologies in smaller surgical corridors with less trauma and greater efficacy.
