Risk is inherent with all surgical procedures. Most endoscopic sinus surgery (ESS) is uncomplicated. Among the many complications inherent with ESS are the neurologic complications, which include cerebrospinal fluid rhinorrhea, traumatic soft tissue and vascular injuries, infection, and seizures. Despite intense review of a patient’s preoperative scans, use of stereotactic image guidance, and an expert understanding of anatomy, neurologic complications occur. An understanding of these complications and how to manage them can help to reduce long-term patient injury as well as help prevent recurrence.
Key points
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There are no easy sinus operations.
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Practical knowledge of anatomy correlated with sinus computed tomography scanning is most important in avoiding complications.
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Cerebrospinal fluid fistula can occur with almost any endoscopic sinus surgery. An understanding of the anatomy of the skull base and a detailed preoperative review of the patient’s CT scans helps prepare the surgeon. Most CSF leaks can be identified and corrected during the operation.
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Intracranial or major vascular injury, if managed immediately, can be minimized in some cases.
Introduction
Risk is inherent with all surgical procedures. Most endoscopic sinus surgery (ESS) is uncomplicated and results in high patient satisfaction. Intraoperative complications can be devastating and include neurologic injury, not the least of which includes intracranial bleeding and infection as well as cerebrospinal fluid (CSF) leaks. These complications can be severe and can lead to long-term morbidity and even death. Despite experience and adequate preparation, complications resulting from sinus surgery occur. With early recognition, many complications can be controlled and potentially reversed.
Introduction
Risk is inherent with all surgical procedures. Most endoscopic sinus surgery (ESS) is uncomplicated and results in high patient satisfaction. Intraoperative complications can be devastating and include neurologic injury, not the least of which includes intracranial bleeding and infection as well as cerebrospinal fluid (CSF) leaks. These complications can be severe and can lead to long-term morbidity and even death. Despite experience and adequate preparation, complications resulting from sinus surgery occur. With early recognition, many complications can be controlled and potentially reversed.
Complications
There are 3 large reviews concerning the complications that occur during ESS. Because other sections within this text deal with orbital and vascular injuries, this section focuses on the neurologic complications that occur during ESS.
Stankiewicz and colleagues reviewed their experience involving ESS in 3402 patients (6148 sides) and noted an overall complication rate of 3.1% or 1.7% per side. Specifically looking at neurologic complications, these investigators recorded a total of 19 (0.55%) CSF leaks. In their series, there was also a 0.06% (2/3402) rate of meningitis associated with ESS. Factors believed to be associated with an increased risk of these complications included age, revision surgery, polyps, and anatomic variations. Given that polyps, anatomic variations, and revision surgery were highly positively correlated with neurologic injuries, these findings suggest that the surgeon is well advised to thoroughly review the preoperative imaging to note factors that may predispose the surgeon to complications.
In a broader review, Ramakrishnan and colleagues reviewed the incidence of major complications after ESS by scanning the nationwide MarketScan Commercial Claims and Encounters database (2009, Thomson Reuters Healthcare). CSF leaks were the single neurologic complication that was investigated. The investigators found that in 40,638 patients, the rate of CSF leak was 0.17%. Most CSF leaks were recognized the day of surgery, and 76% were recognized within 30 days; however, some CSF leaks were recognized as late as 300 days. CSF leaks were less common in the pediatric population. Many surgeons use stereotactic image-guided surgical techniques to help identify the anterior skull base (and thus avoid CSF leaks); however, the use of image guidance was not found to significantly alter the rate of CSF leak in their review.
Similarly, Krings and colleagues used a larger set of health care data to determine the rates of CSF rhinorrhea, bacterial meningitis, dural tears, and injury to the internal carotid artery in 78,944 patients. These investigators identified 103 skull base–related complications in patients undergoing primary ESS and 10 skull base–related complications in patients undergoing revision ESS. The investigators found that although there was no significant difference in skull base complications between primary and revision sinus surgeries, skull base–related complications were significantly more common in patients aged 41 to 65 years and in those undergoing frontal sinus surgery (or all 4 sinuses). There were no differences in skull base complications in surgeons who used stereotactic image guidance compared with those who did not. The investigators did not break down the individual neurologic complications; therefore, this report deals with neurologic complications as a whole, which is in agreement with the rate found by others.
These 3 large reviews show that the rate of neurologic complications is low. There are numerous other reports concerning the individual neurologic complications that are of interest. They are elaborated as follows.
Specific: Cerebrospinal Fluid Leak
Hou and colleagues reviewed their series of ESS and found 19 cases of intracranial complications. The intracranial complications included 14 CSF leaks, 3 direct frontal lobe injuries, 1 incidence of subarachnoid hemorrhage, 2 cases of meningitis, and 3 cases of pneumocephalus. These neurologic complications were not mutually exclusive and highlight the important sequelae that can follow an unintended injury to the anterior skull base.
Similarly, Armengot-Carcellar and colleagues reported a 0.39% incidence of endocranial complications. In 763 patients undergoing ESS, 3 patients developed neurologic complications, including CSF rhinorrhea. One patient developed an intraoperative CSF leak, which was identified and was repaired during the same surgical procedure uneventfully. Another patient developed an intraoperative CSF leak, which was promptly repaired; however, an intracranial abscess was identified on day 7 that required neurosurgical intervention. This procedure was followed by 90 days of intravenous antibiotics. The remaining patient developed severe postoperative headaches after ESS. Both computed tomography (CT) and MRI showed significant pneumocephalus. No defect was found during revision ESS, and no repair was performed; a preoperative sphenoid dehiscence was presumed to be the root cause. The pneumocephalus resolved with conservative management and antibiotics.
Perioperative seizures are rare after ESS, and there are few data in the literature to help elucidate their causes; moreover, they are more likely to be secondary to meningitis, which is one of the most common complications of acute rhinosinusitis. Some investigators have noted seizures in patients with advanced sinus disease with frontal lobe displacement before ESS. Seizures, when they are a complication of ESS, are likely to be related to intracranial bleeding or infection. These seizures can result from injury to the anterior ethmoidal artery or vein ( Fig. 1 ), injury to the cavernous sinus, or injury to dural vessels along the skull base ( Fig. 2 ).
Pneumocephalus is a rare neurologic complication of ESS, and other than those reviews previously described, other case reports of pneumocephalus after ESS seem to imply that this complication is sufficiently manageable with endoscopic closure.
Complication avoidance
Understanding the regional anatomy, performing a detailed review of the patient’s preoperative CT imaging, and experience are the keys to avoiding complications during ESS. Beginning with the anatomy, certain features of the sinuses are important to understand.
The relationship between the maxillary and ethmoid sinuses should be examined in the coronal plane on CT imaging before the start of surgery. The ratio of the posterior ethmoid (just posterior to the basal lamella) to maxillary sinus height should be assessed. Patients with a vertical height ratio of 1:1 (maxillary sinus height to posterior ethmoid height) are less likely to incur skull base injury, simply because the height of the coronal portion of the basal lamella is all the greater, and this leaves more room for missteps in determining where one should enter the posterior ethmoids. However, in patients with a 2:1 or greater than 2:1 maxillary sinus to posterior ethmoid sinus height ( Fig. 3 ), the posterior ethmoid skull base is encountered sooner because of the sloping nature of the skull base in this region and short ethmoid height. Inadvertent injury to the skull base may occur after entering the posterior ethmoids if the patient has a 2:1 or greater than 2:1 ratio and the surgeon enters higher along the basal lamella. Therefore, the surgeon must consider the safest angle of attack ( Fig. 4 ) when moving through the basal lamella and into the posterior ethmoid sinuses. Entering the posterior ethmoids via the medial-inferior aspect of the coronal face of the basal lamella, along the roof of the maxillary sinus or floor of the ethmoid bulla, provides a safer avenue toward the sphenoid sinus and away from the skull base, helping to avoid skull base injury and CSF rhinorrhea.
Once entering the posterior ethmoids, the surgeon is closer to the skull base, which slopes downward in a posterior direction, having begun at the posterior aspect of the frontal recess and terminating at the planum sphenoidale. It is a mistake to assume that this slope is both smooth and two-dimensional because it may appear this way when viewed in the sagittal plane. The midline anterior skull base is variable in structure as described by Keros, because the ethmoid roof is generally higher laterally than it is medially where the cribriform plate is situated. The slope of the ethmoid skull base to the lateral cribriform lamella, which is up to 10 times thinner than the lateral ethmoid roof, is neither symmetric nor uniform in thickness when one side is compared with the other. Therefore, the left skull base may be higher than the right and vice versa. The anterior and posterior ethmoidal arteries traverse the skull base in most cases but can also be suspended below the skull base, making them susceptible to injury. Meyers and Valvassori and Stankiewicz and Chow discuss these variations of anatomy well.
The most useful sinus for identifying the anterior skull base is the sphenoid sinus, which is bounded anteriorly and superiorly by the sphenoid crest, which articulates with the perpendicular plate of the ethmoid bone. Inferiorly and anteriorly, the sphenoid bone becomes the rostrum, which articulates with the vomer of the septum. Lateral to the sphenoid crest are the 2 sphenoid ostia, both of which measure approximately 2 mm in dimension and are within 10 to 20 mm of the floor of the sphenoid or approximately 15 to 20 mm above the choanal arch. The superior turbinates are well-established landmarks for the ostia of the sphenoid sinus, because they are always medial to the superior turbinate and located in the lower one-third to one-half of the vertical portion of the superior turbinate. Entering the sphenoid sinus through the ostium is the safest way to perform a sphenoidotomy. The anterior aspect of the sphenoid bone around the ostium is usually extremely thin, but it thickens both medially near the rostrum and sphenoid crest and laterally near the orbital apex. If resistance is felt, the bone should not be penetrated blindly, rather entered cautiously with a drill or other instrument after the anatomy is confirmed radiographically.
Before surgery on the sphenoid sinus, its CT anatomy should be examined thoroughly in the coronal, axial, and sagittal planes. When in the coronal plane, the presence of a transverse septum within the sinus should alert the surgeon to the possible presence of an Onodi cell ( Fig. 5 ). When an Onodi cell is present, there is an increased incidence of optic nerve injury, because it is closely related to the Onodi cell. The optic nerve should be identified along the lateral and superior walls of the sphenoid sinus, and particular attention should be made to the amount of bone covering the nerve and how much the nerve projects into the sinus itself. Care must be taken when dissecting within the sinus to avoid this lateral and superior structure. Although injury to the optic nerve constitutes a neurologic injury, there is a more thorough discussion of orbital injuries elsewhere in this issue by Devyani Lal and colleagues.
When a lateral recess of the sphenoid sinus is present, the location and anatomy of the maxillary nerve and Vidian nerve should be assessed. Although these structures are not routinely encountered in ESS for chronic rhinosinusitis (CRS), patients with significant sphenoid disease (eg, allergic fungal sinusitis, Samter triad, mucocele) may have dehiscences along these nerves, which may put them at greater risk of injury. The Vidian nerve may project into the sphenoid sinus in up to 64.6% of cases and is susceptible to injury when performing a wide sphenoidotomy in lateral and inferior directions ( Fig. 6 ). Careless use of powered instrumentation or curettes within the sinus may subject these nerves to injury as well. The thickness of the planum sphenoidale should be noted.
