N e u ro l o g i c C o m p l i c a t i o n s and Treatment Kevin C. Welch,

MD

KEYWORDS  Endoscopic sinus surgery (ESS)  Complications  Cerebrospinal fluid (CSF) leak  Subarachnoid hemorrhage  Intracranial hemorrhage  Pneumocephalus  Meningitis  Seizure KEY POINTS  There are no easy sinus operations.  Practical knowledge of anatomy correlated with sinus computed tomography scanning is most important in avoiding complications.  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.  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. 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.

Disclosures: none. Department of Otolaryngology, Northwestern University Feinberg School of Medicine, 676 North St Clair St, Suite 1325, Chicago, IL 60611, USA E-mail address: [email protected] Otolaryngol Clin N Am - (2015) -–http://dx.doi.org/10.1016/j.otc.2015.05.005 0030-6665/15/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved.

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Stankiewicz and colleagues1 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 colleagues2 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 colleagues3 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 colleagues4 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 colleagues5 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

Neurologic Complications and Treatment

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 investigators6 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.7 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 reviews4,5 previously described, other case reports8,9 of pneumocephalus after ESS seem to imply that this complication is sufficiently manageable with endoscopic closure.10 COMPLICATION AVOIDANCE

Understanding the regional anatomy, performing a detailed review of the patient’s preoperative CT imaging, and experience11,12 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

Fig. 1. Axial CT of the head showing an acute hemorrhage involving the gyrus rectus, which resulted from injury to the anterior ethmoidal vessels.

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Fig. 2. Axial noncontrast CT of the head showing acute hemorrhage in the temporal lobe (arrow), which was the result of injury to the dura overlying a dehiscent area within the sphenoid sinus.

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,13 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

Neurologic Complications and Treatment

Fig. 3. Coronal CT of the sinuses immediately posterior to the basal lamella. The short arrows indicate the height of the ethmoid sinuses relative height of the maxillary sinus (long arrows), and in this situation. The height of the maxillary sinus is greater than the height of the ethmoid sinuses by a ratio of greater than 2:1. The posterior skull base is at increased risk after penetration of the basal lamella.

susceptible to injury.14 Meyers and Valvassori15 and Stankiewicz and Chow16 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

Fig. 4. A sagittal CT of the sinuses showing the correct (arrow) and incorrect (arrowhead) angles of attack. If the basal lamella is penetrated high, the risk of injury to the posterior skull base is higher, regardless of ethmoid height.

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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 wellestablished 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 cases17 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.

Fig. 5. Coronal CT of the sphenoid sinus. Transverse septations within the sphenoid sinus signify the presence of Onodi cells.

Neurologic Complications and Treatment

Fig. 6. Coronal CT of the sphenoid sinus showing extensive pneumatization of the sinus that has resulted in pedicled optic nerves (asterisk), Vidian nerves (short arrow), and prominent maxillary nerves (long arrow).

In the axial plane, the contour and bony margins of the internal carotid canal should be assessed. Dehiscent carotid vessels and protrusions into the sphenoid sinus as well as sphenoid sinus septations that insert directly on to the carotid canal bring to light the ease with which these vessels can be injured when entering the sphenoid sinus. Unless the surgeon is removing tumor and is experienced with extended ESS, there is no compelling reason to perform extensive surgery within the sinus, even for fungal ball accumulations. This surgery places the carotid artery at unnecessary risk. Although carotid artery injury is covered in great detail elsewhere in this issue, the neurologic complications resulting from carotid artery include the immediate (hemorrhage/stroke) as well as those resulting from potential repair of the carotid injury (ischemic stroke). After the sphenoid sinus is widely opened, the planum sphenoidale can be clearly identified. This is the lowest point of the anterior skull base, and when the anterior face of the sphenoid sinus is completely removed, the junction between the sphenoid skull base and the ethmoid skull base becomes a readily apparent transition. The posterior ethmoidal cells can be, if necessary, exenterated completely as dissection along the skull base proceeds now in an anterior direction. Generally speaking, a complete skull base dissection is not necessary; however, in some circumstances of advanced sinus disease, a complete dissection along the skull base is advised. It is during these situations that close attention to the anatomy is key to avoiding an injury to the skull base. This dissection is more easily accomplished with a 30 telescope. Anterior to the planum sphenoidale, the bone transitions into the cribriform plate, the lateral cribriform lamella, and the ethmoid roof. This anatomy is best reviewed in the coronal plane, despite its three-dimensional variance. The cribriform plate represents the lowest midline structure in the medial aspect of the nasal vault. The lateral mass of the ethmoid is suspended from the ethmoid roof, which anatomically is part of the frontal bone. The lateral cribriform lamella (a.k.a., lateral lamella) joins the ethmoid roof and the cribriform plate together. The length of the lateral lamella (and hence

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the depth of the cribriform plate) is variable and was studied extensively by Keros13 in several anatomic dissections: 1 to 3 mm (type I), 4 to 7 mm (type II), and 8 to 16 mm (type III). The skull base may also be asymmetric in design. Some18 have shown that type II anatomy is encountered most frequently and that patients with a lower skull base depth (ie, type I) have a lower incidence of skull base injury. The middle turbinate is suspended from the articulation of the lateral cribriform lamella and the cribriform plate; medial to the middle turbinate is the cribriform plate (the lowest point of the skull base), and lateral to the middle turbinate are the lateral lamella and ethmoid roof. There is rarely a compelling reason to venture along the medial aspect of the middle turbinate; in addition to risking injury to the olfactory neurofibers, there is typically no significant disease in this location. By operating in this region, the surgeon is seeking a neurologic injury. However, venturing along the skull base just lateral to the middle turbinate can be fraught with disaster as well, because this anatomically is the lateral lamella, which as previously described is extremely thin and prone to injury and a setup for CSF rhinorrhea. The sagittal portion of the middle turbinate transitions posteriorly as the (third) basal lamella and is visualized in coronal and horizontal planes; when moving from posterior to anterior through the previously opened basal lamella, the surgeon must once again identify the landmarks of the skull base, this time closer to the skull base. As the transition of the ethmoid skull base or ethmoid roof meets the frontal recess, neurologic injury can occur in 2 locations: at the final transition of the ethmoid skull base into the frontal recess or medially where the posterior-medial aspect of the frontal recess meets the anterior attachment of the middle turbinate in the vicinity of the crista galli. These injuries can be made both with hand or with powered instruments. In the most ideal circumstances, it is best to use a 70 telescope for visualization and enter the frontal sinus through its natural drainage pathways. This technique can present a challenge when the uncinate process is attached laterally and superiorly to the lamina papyracea. When it is attached medially to the middle turbinate or the skull base, typically, removal of the uncinate process simply opens the recess wide early in the dissection. However, when the uncinate process inserts laterally, it is frequently adjacent to or involving the agger nasi cell (embryologically, these are of the same origin) and while dissecting medial to the agger nasi to enter the frontal recess, the surgeon is very close to the sagittal attachment of the middle turbinate. Dissection in this region takes a skill and a complete preoperative review of CT imaging. In this situation, the use of stereotactic navigation can be helpful, not so much because it helps to guide the dissection, rather because it helps to understand the frontal recess in 3 dimensions. Beyond a critical understanding of anatomy, the use of image guidance or stereotactic navigation has been believed to assist with surgery and reduce neurologic complications. Citardi19,20 gives excellent reviews of this technology. In addition, there is an excellent discussion of this elsewhere within this issue. The expansion of image guidance systems is such that stereotactic navigation is commonplace.21,22 The American Academy of Otolaryngology–Head and Neck Surgery has drafted a policy statement (http://www.entnet.org/content/intra-operative-use-computer-aided-surgery) that describes the indications for the use of stereotactic navigation in ESS. Stereotactic navigation has the ability to reduce complications if used correctly,21 but the level of evidence supporting what is commonly held by surgeons is lacking.2,3,23 Long-term or randomized studies to evaluate outcomes are difficult to perform and would involve many patients; therefore, the image-guided surgery is considered state of the art rather than standard of care, even for difficult or revision cases.

Neurologic Complications and Treatment

The avoidance of neurologic complications involves the essential preoperative review of the anatomy as it appears on the CT images as well as the ongoing assessment and reassessment of the endoscopic anatomy and the changes in anatomy that result from surgery. Although many believe that stereotactic navigation is helpful during ESS, no amount of navigation can replace experience, knowledge of anatomy, and good judgment. COMPLICATIONS MANAGEMENT

Injury to the anterior skull base is the root of most of the neurologic complications: CSF rhinorrhea, pneumocephalus, dural and parenchymal injuries, and intracranial bleeding. When these complications do occur, how they are managed can make the difference in the patient’s outcome. Transgression of the skull base with or without dural disruption can result in pneumocephalus. It is critically important to differentiate between simple and tension pneumocephalus, the latter being severe and life threatening. There has been some evidence that treatment of simple pneumocephalus with 100% oxygen is helpful in resolution of pneumocephalus when compared with controls.24 Although the management of pneumocephalus after ESS has not been established, DelGuadio and Ingley10 have recommended simple endoscopic closure with grafting in cases in which defects are larger than 15 mm, because patients in their series with smaller skull base defects resolved with conservative management. In cases in which tension pneumocephalus is present, a neurosurgical consultation is highly recommended, because the pneumocephalus in many ways mimics a space-occupying lesion that needs to be urgently decompressed. When the dura is disrupted, the patient develops CSF rhinorrhea with or without pneumocephalus. These defects can be repaired during the operation if the leak is found intraoperatively. Almost any type of living or synthetic tissue can be used to patch a fistula; examples are fascia temporalis, septal or turbinate mucosa, and fascia lata.25–27 Local flaps of septal mucosa, inferior turbinate, or middle turbinate are also successful. The nature of the injury, including defect size, intracranial complications, and whether the patient has the potential for increased intracranial hypertension, all play a role in selecting the graft type and number. Although meta-analysis seems to suggest that graft type may not be a factor,28 this author recommends the following algorithm. When a leak occurs, the surgeon should stop and review the anatomy. Landmarks (eg, posterior wall of the maxillary sinus, lamina papyracea, attachments of the middle turbinate, anterior face of the sphenoid sinus, skull base) should be identified that can help reorient the surgeon. Once the surgeon is reoriented, an attempt should be made to review the preoperative imaging and make use of stereotactic navigation (if present) to help localize the probable site of the leak. The most likely sites of injury include the lateral cribriform lamella near the cribriform plate or fovea ethmoidalis; therefore, the surgeon should review these areas for dehiscences, asymmetries, thinness/thickness, and any bony abnormalities on the preoperative imaging. Additional attention should be directed to the posterior ethmoid sinuses to determine if there is reduced posterior ethmoid height (ie, maxillary-ethmoid ratio 2:1) that predisposes to injury. If the defect cannot be completely identified, some29,30 have advocated for the topical application of fluorescein as a safer alternative to the injection of intrathecal fluorescein, which may be problematic in a patient who is already under anesthesia. If the operating surgeon does not feel equipped to repair the defect, then hemostasis should be obtained, and the nasal cavity should be lightly packed to help apply gentle

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pressure to the defect. The upper and lower aerodigestive tract should be aspirated for blood and antiemetics administered to minimize postoperative nausea. All efforts should be made to minimize increases in intracranial pressure, and particular attention should be directed toward minimizing Valsalva maneuvers during wake-up from general anesthesia. If safe, a deep extubation can be performed and avoidance of nasal positive airway pressure is imperative. The patient should be transferred to a local rhinologist for further management. The efficacy of antibiotic prophylaxis for the prevention of meningitis in patients with postsurgical CSF leaks has not been studied in a prospective manner; however, several retrospective reviews of traumatic CSF leaks have yielded conflicting information. A meta-analysis performed by Brodie31 showed no significant differences in the rates of ascending meningitis in patients treated with and without antibiotics in traumatic anterior skull base CSF leaks. Conversely, Bernal-Sprekelsen and colleagues32 found an incidence of ascending meningitis in 29% of patients treated conservatively (head of bead elevation, bed rest). In a separate study, BernalSprekelsen and colleagues33 found an incidence of ascending meningitis in 36.5% of patients undergoing endoscopic repairs of CSF leaks. This author believes it is prudent to administer perioperative parenteral antibiotics (eg, ceftriaxone) that effectively cover known or expected bacteria involved in patients with CRS. When the patient returns during the postoperative period and there is a question of CSF rhinorrhea, fluid can be sampled and tested for b2 transferrin, a protein isolated to CSF, aqueous humor, and perilymph. Fluid is collected and immunofixation is performed. When b2 transferrin is detected in nasal fluid, this is highly sensitive and specific for CSF rhinorrhea. Although this protein confirms the presence of CSF rhinorrhea, it does not help localize the defect. Another test less frequently performed is an assay for b-trace protein, which is manufactured in the epithelial cells of the choroid plexus; however, it can be detected in serum as well. b2 Transferrin is the preferred laboratory test for the presence of CSF rhinorrhea when the clinical picture is uncertain. A subarachnoid lumbar drain has been advocated in the past for planned treatment of CSF leaks. However, there have been no prospective studies regarding the use and duration of lumbar drains in patients with iatrogenic CSF leaks caused by ESS. In most instances, a lumbar drain is unnecessary for an iatrogenic injury, and some retrospective evidence supports foregoing placement altogether.34 However, a subarachnoid catheter can be used for the administration of intrathecal fluorescein. Multiple studies30,35–39 have shown that the intrathecal administration of fluorescein is safe and effective for the identification of intranasal CSF leaks. A nonophthalmic solution of 10% fluorescein is selected. Precisely 0.1 mL of 10% fluorescein is mixed with 10 mL of bacteriostatic saline or autologous CSF. After the mixture, approximately 5 to 10 mL of the solution is injected into the intrathecal space over 5 to 10 minutes. Significant complications such as seizures have been reported to be dose dependent and related to the rate of injection. Therefore, although not approved by the US Food and Drug Administration for this diagnostic procedure, this mixture is generally believed to be safe, and many find fluorescein helpful in confirming the site(s) of CSF rhinorrhea and for confirming that they are successfully closed. Endoscopic repair of CSF leaks has been reported to be successful in 90% to 97%26,28 during a first attempt. Once the site of the leak is identified and prepared, the surgeon should adhere to 3 goals: (1) the safe and successful closure of the leak; (2) the maintenance of sinus function; and (3) the prevention of postoperative complications. Preparation of the surgical site is undertaken by widely opening the remaining sinuses to completely expose the skull base and defect. If exposure of the defect

Neurologic Complications and Treatment

requires the removal of the middle turbinate (this is rarely necessary except in cases of spontaneous leaks), then, its resection should be complete to prevent postoperative lateralization of the middle turbinate remnant and iatrogenic frontal recess obstruction. If the middle turbinate is removed, it should be preserved for later use as grafting material. Once the defect is fully delineated, the mucosa surrounding the defect is stripped and ablated with bipolar electrocautery 3 to 4 mm beyond the bony defect rim. The size of the defect is then measured using a trimmed ruler. For defects smaller than 5 mm, it is likely that the defect will heal with a combination of osteoneogenesis and soft tissue fibrosis; therefore, we do not recommend preparation of the epidural space or placement of a bone graft to avoid increasing the size of the defect. Simple preparation of the mucosa along the defect with the placement of an overlay graft (eg, nasal floor or septal mucosa, middle turbinate mucosa, temporalis fascia, fat) dressed with a thin layer of fibrin sealant sufficiently patches most leaks of this size or smaller (Fig. 7). This author prefers to use a composite graft or pedicled nasoseptal flap40 for the repair of defects greater than 5 mm. In these circumstances, a middle turbinate composite (mucosa/bone) graft is an excellent choice for repair, because the bone of the middle turbinate is similar in density when compared with the bone of the cribriform plate and anterior skull base. Other options include harvesting septal bone and septal mucosa as free grafts. Both these techniques work well for defects greater than 5 mm. Defects greater than 10 mm are closed in a multilayered fashion with underlay bone grafting (septal bone, middle turbinate bone) to reconstitute the native skull base anatomy. A pedicled nasoseptal flap can be harvested off the ipsilateral septum and transposed over the defect. Because this flap maintains its native blood supply (sphenopalatine via the posterior nasal and nasoseptal artery), it provides viable and bulky tissue coverage. This flap has become the workhorse of anterior skull base reconstruction and works well in spontaneous and iatrogenic cases. This flap may provide adequate coverage of the entire ethmoid skull base (Fig. 8) as well as the sphenoid skull base. Modifications have been described to help the flap extend into the frontal recess.

Fig. 7. Endoscopic view of the left ethmoid sinuses after a free mucosa graft (short arrows) has been placed over an ethmoid skull base injury that resulted in CSF rhinorrhea. A frontal stent (long arrow) helps hold the graft in place.

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Fig. 8. Endoscopic view of the left ethmoid skull base, which sustained a large defect caused by microdebrider injury. This defect was repaired using a pedicled nasoseptal flap (arrowheads). The frontal sinus stent (long arrow) helps hold the flap in place. The inferior turbinate (IT), maxillary (M) sinus, and sphenoid (S) sinus can be visualized and are intentionally widened to prevent postoperative obstruction.

Regardless of reconstructive technique, the cavity is gently packed with Gelfoam and then with a nonabsorbable pack. The patient should be observed for 48 to 72 hours after the procedure. It is prudent to consult neurosurgery and to have the patient undergo postoperative imaging to assess for pneumocephalus and intracranial bleeding. Although routine imaging after uncomplicated skull base surgery has not been shown to alter postoperative management,41 surgeons should consider iatrogenic leaks to be unexpected. Given the current medical and legal climates, thorough evaluation of this complication is indicated. It is best to involve a neurosurgical colleague when more significant intracranial and neurologic complications do occur. These complications include meningitis, seizures, and intracranial bleeds. SUMMARY

Neurologic complications can occur despite the best of intentions and expert treatment of patients with CRS. Knowing where these complications occur and taking extra time to identify these critical areas can help reduce the likelihood of causing an injury. Once a neurologic complication occurs, prompt and comprehensive action can make the difference in outcomes. REFERENCES

1. Stankiewicz JA, Lal D, Connor M, et al. Complications in endoscopic sinus surgery for chronic rhinosinusitis: a 25-year experience. Laryngoscope 2011; 121:2684–701. 2. Ramakrishnan VR, Kingdom TT, Nayak JV, et al. Nationwide incidence of major complications in endoscopic sinus surgery. Int Forum Allergy Rhinol 2012;2:34–9.

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3. Krings JG, Kallogjeri D, Wineland A, et al. Complications of primary and revision functional endoscopic sinus surgery for chronic rhinosinusitis. Laryngoscope 2014;124:838–45. 4. Hou W, Wen Y, Wang Z, et al. Clinical analysis of the cranial complications of endoscopic sinus surgery. Acta Otolaryngol 2013;133:739–43. 5. Armengot-Carcellar M, Hernandez-Sandemetrio R. Endocranial complications of endoscopic sinus surgery: learning from experience. Int J Otolaryngol Head Neck Surg 2014;3:298–303. 6. Stumpe MR, Sindwani R, Chandra RK. Endoscopic management of sinus disease with frontal lobe displacement. Am J Rhinol 2007;21:324–9. 7. Llorente Pendas JL, del Campo A, Perez Vazquez P, et al. Complicated sinusitis and nasal endoscopic surgery. Acta Otorrinolaringol Esp 2003;54:551–6 [in Spanish]. 8. Emmez H, Durdag E, Uslu S, et al. Intracerebral tension pneumocephalus complicating endoscopic sinus surgery: case report. Acta Neurochir (Wien) 2009;151:1001–2. 9. Whitmore RG, Bonhomme G, Balcer LJ, et al. Tension pneumocephalus after endoscopic sinus surgery: case report of repair and management in absence of obvious skull base defect. Ear Nose Throat J 2008;87:96–9. 10. DelGaudio JM, Ingley AP. Treatment of pneumocephalus after endoscopic sinus and microscopic skull base surgery. Am J Otolaryngol 2010;31:226–30. 11. Stankiewicz JA. Complications of endoscopic intranasal ethmoidectomy. Laryngoscope 1987;97:1270–3. 12. Stankiewicz JA. Complications in endoscopic intranasal ethmoidectomy: an update. Laryngoscope 1989;99:686–90. 13. Keros P. On the practical value of differences in the level of the lamina cribrosa of the ethmoid. Z Laryngol Rhinol Otol 1962;41:809–13. 14. Moon HJ, Kim HU, Lee JG, et al. Surgical anatomy of the anterior ethmoidal canal in ethmoid roof. Laryngoscope 2001;111:900–4. 15. Meyers RM, Valvassori G. Interpretation of anatomic variations of computed tomography scans of the sinuses: a surgeon’s perspective. Laryngoscope 1998;108:422–5. 16. Stankiewicz JA, Chow JM. The low skull base: an invitation to disaster. Am J Rhinol 2004;18:35–40. 17. Tan HK, Ong YK. Sphenoid sinus: an anatomic and endoscopic study in Asian cadavers. Clin Anat 2007;20:745–50. 18. Ali A, Kurien M, Shyamkumar NK. Anterior skull base: high risk areas in endoscopic sinus surgery in chronic rhinosinusitis. Indian J Otolaryngol Head Neck Surg 2005;57:5–8. 19. Citardi MJ. Principles of registration. In: Citardi MJ, editor. Computer-aided otorhinolaryngology – head and neck surgery. New York: Marcel Dekker; 2002. p. 49–71. 20. Citardi MJ. Image-guided functional endoscopic sinus surgery. In: Citardi MJ, editor. Computer-aided otorhinolaryngology – head and neck surgery. New York: Marcel Dekker; 2002. p. 201–22. 21. Reardon EJ. Navigational risks associated with sinus surgery and the clinical effects of implementing a navigational system for sinus surgery. Laryngoscope 2002;112:1–19. 22. Metson R. Image-guided sinus surgery: lessons learned from the first 1000 cases. Otolaryngol Head Neck Surg 2003;128:8–13. 23. Smith TL, Stewart MG, Orlandi RR, et al. Indications for image-guided sinus surgery: the current evidence. Am J Rhinol 2007;21:80–3.

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