Preoperative Planning

It is extremely important that the ESS surgeon conduct a thorough review of the patient’s anatomy and pathology before undertaking surgery. The patient’s history of prior ESS and facial trauma should be elicited, because these may be associated with anatomic abnormalities. The medication profile and other potential risks of hemorrhage should be ascertained. The endoscopic examination should carefully judge whether the disease or prior surgery could potentially compromise visualization of landmarks during ESS. The sinus computed tomographic (CT) scan should be carefully studied, and this scan must always be available for intraoperative review. The surgeon should schedule surgery only if it is in the planned surgical procedure and if they have the tools required for such procedure such as image guidance systems (IGS) and powered and handheld instrumentation. Surgeons should be aware of the limitations of their expertise and technology. For example, although IGS been advocated for those with complex anatomy, polyps, tumors, frontal and sphenoid sinusotomy, and revision surgery, its use may not necessarily prevent orbital complications. Novice surgeons must be carefully proctored; they must practice dissection on cadaver specimens first, because ESS has a steep learning curve. However, constant vigilance by even the experienced sinus surgeon is mandated.

Intraoperative Considerations

The eyes must always be draped into the field and should not be covered but taped with a paper or transparent tape. Intraoperatively, the surgeon should consistently inspect and palpate the eyeball, especially when working close to the lamina papyracea or skull base. Assistants should be educated and encouraged to communicate urgently should they notice any orbital proptosis while the surgeon’s view is focused on the endoscopic monitor. Surgery should be terminated if visualization is unsatisfactory and bleeding cannot be controlled. The surgeon should be familiar with the higher risk of orbital injury associated with powered instrumentation. Powered instrumentation such as microdebriders should be used only when the cutting edge can be clearly visualized endoscopically. These instruments should be used parallel to the lamina papyracea and not push toward the orbit. Intraoperative image guidance should be carefully calibrated, and adjustments to errors of calibration should be constantly made during ESS in conjunction with the surgeon’s understanding of the relevant anatomy.

Computed Tomographic Review

The surgeon must develop a systematic manner of reviewing CT scans to identify those with higher risk of orbital injury. The authors provide a suggested checklist ( Table 1 ). Orbital anatomy in relationship to the paranasal sinuses must be conducted in all 3 planes. Subtle protrusion of the orbit or orbital contents into the ethmoidal space may be better recognized on axial scans. Any dehiscence or thinning of the lamina papyracea must prompt closer evaluation because prolapsed orbital contents may be mistaken for a polyp or inflammatory sinus mucosa ( Fig. 1 ). Presence of pathologic conditions such as mucocele or polyposis expanding or eroding into the orbit must be identified.

Dehiscence or thinning of the lamina papyracea must prompt closer evaluation because prolapsed orbital contents may be mistaken for a polyp or inflammatory sinus mucosa or lead to inadvertent orbital entry. ( A ) Coronal CT demonstrates a focal defect in the left lamina papyracea with resultant protrusion of orbital fat into the adjacent ethmoid ( white arrow ). The patient denied any history of facial trauma or sinonasal surgery. ( B ) Coronal CT depicts a defect in the right lamina papyracea ( white arrow ) related to prior ESS.

The maxillary ostium usually lies in the same parasagittal plane of the medial wall of the orbit, but when the lamina papyracea is positioned medial to the maxillary ostium owing to hypoplasia of the ethmoidal cells, there is higher risk of orbital penetration during ESS ( Fig. 2 ). When the maxillary sinus is hypoplastic, the uncinate is usually hypoplastic or laterally displaced over the orbit, predisposing the patient to orbital penetration during ESS. A similar situation exists in those with the silent sinus syndrome when both the lamina papyracea and the orbital floor are at risk of injury ( Fig. 3 ). In this situation, one should be prepared to use handheld instruments as opposed to powered microdebriders. Retrograde uncinectomy technique here may be safer compared with anterograde uncinectomy with a sickle knife.

( A ) The maxillary ostium ( white arrowhead ) usually lies in the same parasagittal plane as the medial wall of the orbit ( white arrow ). ( B ) When the lamina papyracea ( white arrow ) is positioned medial to the maxillary ostium ( white arrowhead ) owing to hypoplasia of the ethmoidal cells, there is higher risk of orbital penetration during ESS. ( C ) Hypoplasia of the maxillary sinus can result in even further lateralization of the maxillary ostium ( white arrowhead ) relative to the lamina papyracea ( white arrow ). Incidentally, the soft tissue structure between the left middle and inferior turbinates ( white star ) was an inflammatory polyp. The dotted line represents a parasagittal plane along the medial wall of the orbit.

( A ) Axial CT of silent sinus syndrome is associated with marked volume loss causing inward retraction of the right maxillary sinus walls ( white arrows ). ( B ) On coronal CT, the imploded right maxillary sinus exhibits a low-lying orbital floor ( white arrow ) and an uncinate process that is lateralized and draped over the orbit ( white arrowhead ). Both the lamina papyracea and the orbital floor are consequently at risk of iatrogenic injury.

The position of the AEA and the PEA must be located on the scans. These arteries are branches of the ophthalmic artery and leave the orbit between the medial rectus and superior oblique muscles within the ethmoidal skull base. The AEA travels within a bony mesentery below the level of the skull base in up to 36% of cases, with a dehiscence rate ranging from 6% to 66%. A long lateral lamella or the presence of supraorbital pneumatization is associated with a low-hanging AEA. The AEA is considered to be the posterior boundary of the frontal recess and lies close to the attachment of the middle turbinate basal lamella at the skull base, whereas the PEA lies in the ethmoidal skull base just anterior to the face of the sphenoid sinus ( Fig. 4 ). An injured ethmoidal artery may retract into the orbital cavity and cause a rapidly expanding retrobulbar hematoma that can result in blindness if not quickly recognized.

( A ) Coronal CT demonstrates both AEAs to be pedicled ( white arrows ) with air cells separating them from the ethmoid roof, an anatomic variant that predisposes to transection during ESS. ( B ) Sagittal CT illustrates the typical distance between the AEA and PEA. The AEA ( white arrow ) is typically located near the posterior aspect of the globes, while the PEA ( white arrowhead ) is found in close proximity to the sphenoid sinus.

In addition, one must recognize and be familiar with implications of variations of ethmoidal pneumatization. The sphenoethmoidal (Onodi) cell may be related to the optic nerve and even the internal carotid artery in its lateral wall. The surgeon therefore encounters these structures during ethmoidectomy, before undertaking sphenoidotomy. Not recognizing this variation may thus result in catastrophic injury, especially when extensive disease or polyposis obscures the anatomy. The optic nerve may be dehiscent in the lateral sphenoid sinus or lie in the Onodi cells in approximately 3.4% to 14% of cases ( Fig. 5 ). The optic canal can travel through a well-pneumatized sphenoid in 3% cases and may be mistaken for a partition if the CT is not carefully reviewed ( Fig. 6 ). The infraorbital nerve lies just lateral to an infraorbital (Haller) cell and may be injured while addressing this cell ( Fig. 7 ). Higher frontoethmoid dissection in the presence of Type 3 or Type 4 frontal cells may also place at risk the superior orbital contents, including the superior oblique muscle.

Recognizing the presence of an Onodi cell preoperatively is important to minimize risk to the optic nerve. Coronal CT demonstrates the close relationship between an Onodi cell ( white star ) and focal dehiscence in the right optic canal ( white arrowhead ). The right sphenoid sinus, which exhibits mild mucosal thickening, is positioned more inferiorly ( white arrow ).

( A ) Coronal CT and ( B ) axial CT reveal anterior clinoid pneumatization ( white arrow ), a variant that is important to recognize to make certain that the optic canal ( white star ) is not mistaken for a partition in the sphenoid sinus. When taking down the sphenoid septum, it is also important to recognize its potential insertion on to the optic canal ( white arrowhead, B ).

The infraorbital nerve ( white arrow ) lies just lateral to an infraorbital (Haller) cell ( white star ) and may even be partially incorporated into its wall. Recognizing this close anatomic relationship is critical to avoid nerve injury.

Postoperative Considerations

All patients must be counseled to watch and report immediately any changes in vision, color vision, double vision, eye pain, watering from the eye, bruising, and emphysema. Should any orbital injury during surgery be recognized, the patients should be advised of it and be placed on the appropriate therapeutic interventions as discussed in the following section.