vey reveals the extent of the lesion that can now be removed under visualization from areas that are not directly visible behind the orbital rim and any areas abutting the dura (Figure 1). A 70-degree tip is on occasion required for a better view of the internal aspect of the superior orbital rim and the anterior wall of the frontal sinus for those lesions that abut these areas. The periosteum is reattached and the skin incision closed.

Use of the endoscope as a teaching aid

The small surgical field available when operating within the orbital confines makes it difficult for a supervising surgeon to view the trainee’s surgery. The subperiosteal space is a potential space that allows retraction of the orbital contents by placing a retractor against the orbital periosteum. The space thus created is ideally suited for placement of a video endoscope that can be used to observe surgery within the orbit.17 The supervising surgeon usually holds the endoscope while the operating surgeon may either view the surgical field directly or observe it on the video monitor. The light from the endoscope and the magnification provided also aid in the dissection. In most cases, the endoscope is rested on the orbital rim or, less frequently, on a retractor to provide the required view and also to minimize fogging. On occasion, a shorter and narrower endoscope such as a pediatric video-otoscope or a flexible endoscope may be used so as not to compromise the surgeon’s access or view. This may be particularly useful in the transcaruncular approach to the medial orbital wall, where the larger endoscope may impede the surgeon’s access through the small incision. Endoscopic supervision is most applicable to procedures such as deep lateral wall (Figure 5) or medial wall orbital decompression, orbital fracture repair and lesions involving the orbital roof. Endoscopes used may vary from 0- to 70-degree tips dependant on the location of the surgical field. In addition, the procedures may be recorded onto videotape and reviewed by both consultant and trainee. Surgical drains are not usually placed after transorbital endoscopic surgery. Postoperative

Figure 5 Endoscopic view of deep lateral orbital wall allowing excellent visualization during bone removal with a burr.

care includes monitoring of pupils and vision every 4 hours for the first day as for any orbital procedure.

Complications

The complications encountered are those of the orbital procedure rather than attributable to use of the endoscope itself. In fact, use of the endoscope minimizes chances of complications such as dural tear during orbital roof lesion removal or deep lateral orbital decompression.

Discussion

The primary advantage of transorbital endoscopic surgery is avoidance of bone removal for adequate exposure. Furthermore, the use of a more minimally invasive technique enables the surgeon to treat surgical patients on an outpatient basis, thus reducing length of hospitalization in comparison with the traditional postoperative management of a lateral orbitotomy or craniotomy. Additional advantages include increased illumination and magnification and an extended viewing angle, all of which enable good visualization of the surrounding bone and dura. This facilitates a safer and more meticulous removal of bone or tissue abutting the dura and perhaps also decreases the risk of a cerebrospinal fluid leak in comparison with procedures during which an endoscope is not used.

Alternative approaches to the superior orbit and orbital roof include lateral orbitotomy, extended superolateral orbitotomy (removal of lateral wall with adjacent temporal or parietal bone), and transcranial orbitotomy.19 These approaches provide good exposure but are possibly associated with increased risk of morbidity because of the bone removal and greater tissue dissection. Although a supraorbital endoscopic approach to the anterior cranial base and frontal sinus (via a 1.5-cm craniotomy above the supraorbital rim) has also been described in the neurosurgical literature,20 its use may be limited in lesions which also extend into the superior orbit.

Transorbital endoscopy is also specially useful while performing decompression of the deep lateral orbital wall. The removal of the deep lateral wall including the marrow space has been shown to increase the efficacy of orbital decompression in cases of thyroid orbitopathy.21 The use of the endoscope during this procedure aids in visualization and minimizes complications such as cerebrospinal fluid leaks.

A clean operating field is essential to the success of transorbital endoscopic surgery, especially since the operating area is usually limited. Meticulous hemostasis aided by effective suction and judicious cautery greatly aids in visualization and prevents soiling of the endoscope. The use of different-sized malleable retractors is also essential to provide adequate viewing space. Because diffuse bleeding from the bone is commonly encountered, the use of an adrenaline-soaked tamponade (for approximately 5 minutes) or bone-wax may be required. Incorporating these guidelines will facilitate transorbital endoscopic surgery.

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