External Approaches to the Paranasal Sinuses and Skull Base



10.1055/b-0034-79209

External Approaches to the Paranasal Sinuses and Skull Base

A. Janjua, I. J. Witterick

Introduction


External approaches to the sinuses were largely employed before the introduction of endoscopy. In the setting of inflammatory sinus disease, external approaches facilitated open visualization of the sinus mucosal lining, removal of diseased sinus lining and the creation of dependent (and presumed functional) drainage pathways from the sinus cavities into the nose. The introduction of rod lens technology and advances in clinicians’ understanding of the physiologic pattern of sinus drainage have largely led to the replacement of external approaches with endoscopic techniques, which preserve mucosal lining and restore the patency of the natural drainage pathways of the sinuses (toward which the cilia direct mucous outflow from the sinuses).


More recently, external approaches have continued to be employed when open access to the sinuses is required for the surgical removal of sinonasal tumors. Despite the development of endoscopic techniques in the 1970s and 1980s to address inflammatory sinus disease,16 the removal of nasal and sinus tumors continued to occur through external approaches. Only recently has the superiority of en bloc tumor resection been challenged,7 and the development of advanced endoscopic instrumentation allowed for endoscopic removal of nasal and sinus tumors.


Still, endoscopic approaches have some limitations and external approaches to the sinuses may be required (and, indeed, superior) in situations where substantially wider exposure to the sinuses is required;8 although, several authors have described more extensive endoscopic exposures to tackle these situations.911 Nonetheless, modern advanced endoscopic nasal surgery requires specialized and costly endoscopic instruments and technologies, to which some institutions may not have access. As such, all rhinologists should be familiar with external approaches to the paranasal sinuses. Due to decreased instruction regarding external approaches during surgical training, it is important that rhinologists understand their potential pitfalls and complications, and the preventive steps that may be taken to minimize them.


As with any surgery, bleeding that obscures visualization may lead to intraoperative complications, so minimizing intraoperative hemorrhage is essential. In each of the approaches described in this chapter, key steps to prevent intraoperative blood loss and avoid poor surgical visualization will be described ( Fig. 11.1 ).


A detailed review of the patient′s preoperative status and imaging is paramount in identifying potential complications and so minimizing their occurrence. Careful review of preoperative computed tomography scans to evaluate the integrity and height of the skull base is crucial, particularly for preventing intracranial complications. As the surgeon proceeds posteriorly, the skull base is not parallel to the hard palate; rather, it slopes inferiorly. The degree of the slope can be ascertained from preoperative imaging and this can alert the surgeon to the potential for violation of the cranial base posteriorly.


It is also prudent to review the patient′s ophthalmologic history, and document gross visual acuity and ocular range of motion. If abnormalities are suspected, a formal ophthalmologic consultation should take place. May and colleagues12 reported that the only significant difference between their analysis of complications during traditional sinus surgery versus functional endoscopic sinus surgery techniques was orbital complications, particularly retrobulbar hematoma. In their series of 2,108 patients, they reported minor and major orbital complication rates of 1.7% and 0.05%, respectively.


With the above issues taken into consideration preoperatively, complications may thereby be minimized. Still, the surgeon′s experience with open sinus surgical techniques may be the most crucial factor in determining the risk and type of complications that may ensue during external sinus surgery.



External Approaches to the Maxillary Sinus



Introduction


George Caldwell and Henri Luc first described an anterior approach to the maxillary sinus in the late 1800s. Their initial description was that of an upper gingivobuccal sulcus incision, entrance to the maxillary sinus via the canine fossa, complete stripping of the maxillary sinus mucosa and creation of an inferior meatal antrostomy.13 More recently, the term Caldwell–Luc is generally used to describe any form of access to the maxillary sinus via an upper gingivobuccal sulcus incision and entrance via the anterior wall of the maxillary sinus.

Schematic depiction of the paranasal sinuses and the surrounding major vascular anatomy. Depicted are the infraorbital artery between the roof of the maxillary sinus and orbit and the course of the facial artery supplying the external midface. The ophthalmic artery gives rise to the anterior and posterior ethmoid arteries which traverse the roof of the ethmoid sinuses (not shown).


Indications


External approaches to the maxillary sinus are indicated under the following conditions:




  • Septated or lateral inflammatory disease within the maxillary sinus that is either refractory to endoscopic techniques or difficult to access transnasally



  • The necessity for wide exposure of the posterior wall of the maxillary sinus (i.e., in juvenile angiofibroma resection, pterygopalatine fossa or infratemporal fossa exploration, and tumor resection)



  • For exposure of the orbital floor during transantral repair of orbital floor fractures



  • To facilitate instrumentation of the anterior wall of the maxillary sinus via endoscopic techniques (i.e., during removal of a mass lesion involving the anterior wall mucosa)



  • For direct closure of select oroantral fistulas (although the majority of these may be resolved via endoscopic creation of an unimpeded drainage pathway from the maxillary sinus into the nasal cavity and simple intraoral fistula closure with oral mucosal rotation flap techniques)



  • For transantral ligation of the maxillary artery in the setting of refractory epistaxis; however, this approach has largely been replaced by transnasal endoscopic sphenopalatine artery ligation.

Computed tomography of oroantral fistula (arrow) and chronic maxillary sinusitis.


Complications: Prevention and Management



Oroantral Fistulas

A persistent communication between the maxillary antrum and the maxillary alveolus (or gingivobuccal sulcus) may result following access to the maxillary sinus via an incision in this location. The reported incidence of an oroantral fistula is 1.0% ( Fig. 11.2 ).14


Prevention of postoperative fistulas may be achieved by the creation of a low-resistance drainage pathway from the maxillary sinus into the nose (most commonly via middle meatal antrostomy), to ensure adequate postoperative intranasal sinus drainage and to avoid excessive pressure or tension on the incision line. Resection of the fistula tract (if longstanding and subsequently epithelially lined) and utilization of maxillary sinus and/or oral mucosal flaps to interpose tissue over the fistula site should be performed. Planning an incision that preserves at least 5 mm of buccal mucosa away from the sulcus allows for adequate closure and good mucosal approximation, thereby minimizing the risk of fistula. Saline solution or other nonalcoholic mouth rinses are indicated for 1 to 2 weeks after surgery, to keep the area clean and to prevent postoperative infection.



Maxillary Artery Injury

The maxillary artery lies in close proximity to the posterior wall of the maxillary sinus. Avoiding violation of the posterior wall prevents the significant hemorrhage that can occur as the result of injury to this artery. Delayed hemorrhage following cauterization of the artery can occur, albeit rarely, and may result in significant postoperative epistaxis. Furthermore, posterior extension of a middle meatal antrostomy may result in injury to the sphenopalatine artery (the terminal branch of the maxillary artery) as it enters the nose immediately posterior to the crista ethmoidalis.



Infraorbital Nerve (V2) Dysesthesia

Dental numbness, facial pain and local hypoesthesia may occur as the result of injury to the infraorbital nerve or its superior alveolar branches. Surgical exposure involves reflection of soft tissue from the face of the maxillary sinus. The periosteum is incised and elevated to provide adequate exposure to the bony anterior maxillary sinus wall. During elevation, care must be taken to identify the infraorbital nerve and prevent injury or division. The pupil is an approximation in the sagittal plane where the infraorbital nerve exits the surface of the facial skeleton. The use of cautery in close proximity to the nerve, or failure to avoid excessive retraction of the cheek soft tissues overlying the nerve, will result in postoperative nerve dysfunction. Excessive removal of the anterior bony wall of the maxillary sinus is routinely complicated by anterior superior alveolar nerve dysfunction.


Injury to the infraorbital nerve may also occur as a result of instrumentation or violation of the superior wall of the maxillary sinus. Care must be taken when using instruments in this area or when stripping mucosa from the roof of the maxillary sinus, as the nerve may or may not have a bony covering in this location. The nerve may simply be hanging in a soft tissue mesentery within the roof of the maxillary sinus, making careful instrumentation of the area essential.


Violation or removal of the posterior wall of the maxillary sinus provides exposure of the pterygopalatine fossa and may also lead to injuries of the descending palatine branches from the maxillary nerve, resulting in numbness of the ipsilateral soft and hard palate.


Localized numbness of the upper lip resulting from cutting through the direct cutaneous sensory nerves when performing the gingivobuccal sulcus incision occurs frequently; however, it is usually temporary and resolves following healing and sensory nerve reinnervation. During healing, patients often complain of a numb and achy sensation along their ipsilateral maxillary dentition for several months postoperatively, and should be counseled appropriately preoperatively. Long-term facial numbness or paresthesia has been reported in ~ 9.0% of patients ( Fig. 11.3 ).14

Schematic depiction of the paranasal sinuses and surrounding sensory nerves as well as the associated cutaneous distributions. a Sagittal view of the first and second divisions of the trigeminal nerve and their proximity to the sinuses. b Illustration of the cutaneous distribution of the three major branches of the trigeminal nerve. The cutaneous branches of V1 and V2 that are at particular risk during external approaches to the sinuses are labelled.


Epiphora

The creation of a pathway for postoperative ventilation and drainage of the maxillary sinus occurs either via inferior meatal antrostomy or, more commonly, middle meatal antrostomy. Care must be exercised when creating either form of maxillary antrostomy to avoid injury to the nasolacrimal duct (NLD) or significant scarring, which may result in epiphora. Inadvertent lacrimal system injury occurs frequently, however, the exact incidence and prevalence is not known. Most injuries are believed to heal spontaneously, often without resultant symptomatic epiphora.


During inferior meatal antrostomy, avoidance of the anterior/superior region of the inferior meatus (the area of Hasner′s valve) minimizes this risk. Planning an inferior meatal antrostomy in the posterior two-thirds of the inferior meatus is prudent to avoid this complication.


During middle meatal antrostomy, the risk of injury to the NLD may be minimized by ensuring that the maxillary antrostomy is not extended too anteriorly along the lateral nasal wall. Should damage to the NLD occur, intubation of the lacrimal apparatus via the lacrimal puncta with temporary silicone tubing may be performed to stent the NLD during the healing phase; however, this procedure is rarely necessary.


In recurrent, severe or refractory cases of scarring of the lacrimal drainage apparatus, a formal dacryocystorhinostomy may be performed to allow lacrimal drainage superiorly in the nose, proximal to the area of NLD stenosis. This may be achieved endoscopically or through an open approach. Mucosa of the anterior lateral wall of the nose is elevated over the superior segment of the bony nasolacrimal canal. The medial wall of this bony canal is removed (often with a fine drill) and the NLD is entered medially and marsupialized to allow for free lacrimal flow. Once again, temporary silicone tubing may be placed during the healing phase and removed postoperatively in the office setting. Alternatively, a permanent glass Lester Jones tube may be inserted, should permanent stenting be required to ensure long-term patency.



Intranasal Crusting

Intranasal crusting usually results from postoperative exposure of bone or cartilage following stripping of the overlying mucosa. An intraoperative technique that minimizes removal of mucosal lining—and so does not expose the underlying bone or cartilage—significantly minimizes this complication. Frequent postoperative saline irrigation may minimize excessive crusting and promote more rapid mucosalization in the event that inadvertent mucosal stripping occurs or when pathologic mucosal lining must be removed. Intranasal crusting is associated with a foul odor; if crusting does occur, an intensified saline irrigation regimen, frequent debridement, and systemic antibiotics may be required.



Packing-Related Complications

It is usually not necessary to insert packing into a maxillary sinus following surgery. Should packing be required, either dissolvable or formal nasal packing may be used. The advantage of resorbable nasal packing is that it does not need to be removed postoperatively, a process which may be quite uncomfortable for the patient. Should the surgeon elect to use formal, nondissolving packing, care must be taken to ensure that all packing is secured, but easily removable from the nose, such that migration and aspiration of the packing cannot occur and no packing is inadvertently retained. Regardless of the type of nasal packing used, appropriate postoperative antibiotic coverage should be provided to prevent secondary infection. Of note, when packing is placed, early postoperative saline lavage may not be performed; rather, lavage should be initiated following packing removal.



Toxic Shock Syndrome

Toxic shock syndrome is a rare and potentially fatal infectious complication related to nasal packing. Most cases result from the release of an exotoxin produced by Staphylococcus aureus. Diagnostic criteria from the U.S. Centers for Disease Control and Prevention include a fever > 102°F (39°C), diffuse macular rash, desquamation, and hypotension; in addition, at least three organs must be involved. The presentation usually occurs within 48 hours of packing placement and has been associated with various types of nasal packing. Although antibiotics are commonly recommended for the prevention of toxic shock syndrome and other infectious complications, their efficacy is subject to debate.1517 Treatment includes packing removal, nasal cultures, debridement of necrotic or infected tissue, resuscitation of blood pressure, and the administration of antistaphylococcal antibiotics.



Hyperostotic Bone Formation

Following Caldwell–Luc approaches, substantial bony changes frequently occur along the violated anterior wall or concentrically within the maxillary sinus. This complication is more pronounced following mucosal stripping, but is not limited to this procedure. Hyperostotic bone formation may cause difficulty with respect to interpreting postoperative imaging and render subsequent access to the sinus difficult.



Cheek Edema

Cheek edema is a common occurrence following Caldwell–Luc approaches to the maxillary sinus, and is seen in 89% of patients.14 Postoperative icing for 24 to 48 hours and head elevation may minimize its severity.



Facial Cellulitis/Abscess

Secondary infection of the nasal vestibule or facial soft tissues overlying the maxillary area, most commonly caused by Staphylococcus aureus, may occur following external approaches to the maxillary sinus ( Fig. 11.4 ). Subsequent abscess collection may also occur ( Fig. 11.5 ). Patients should be given perioperative antibiotics to minimize the risk of these complications.

Nasal vestibulitis following Caldwell–Luc approach to the maxillary sinus.
Computed tomography displaying signs of right facial cellulitis/abscess following a Caldwell–Luc approach.


Facial Asymmetry

Excessive removal of the anterior bony wall of the maxillary sinus may result in various alterations in facial cosmesis. Excessive removal of the medial vertical maxillary buttress may result in depression or collapse of the lateral aspect of the lower lateral cartilage; the visual appearance is that of flattening of the lateral aspect of the nasal ala.


Excessive removal or weakening of the lateral maxillary buttress is further thought to lead to an increased potential for lateral facial asymmetry. It has been suggested that this risk may be minimized by leaving intact the bony wall lateral to the midpupillary line.18 The reported rate of asymmetry following resolution of postoperative facial swelling is 2 to 3%.19



Dental Complications

Injury to the maxillary tooth roots (most commonly the molars, as theirs roots project further into the maxillary sinus) may occur during surgical entrance to the maxillary sinus via its anterior wall, or during removal of the sinus mucosal lining in the setting of maxillary tooth roots that project superiorly into the sinus. Care must be taken to avoid low entrance into the maxillary sinus or removal of excessive bone inferiorly (along the anterior wall of the maxilla) when making the bony window for visualization within the maxillary sinus. Preoperative imaging may identify tooth roots that project into the maxillary sinus, and so are at increased risk. In a series of 670 Caldwell–Luc procedures, the rate of devitalized dentition was reported to be 0.4% (n = 2).14 These patients required root canal work to resolve the dental symptoms.



External Ethmoidectomy


The surgical technique for external ethmoidectomy was first described in 1933 by Ferris Smith.20 Since then, several modifications have been described, which include the use of a variety of facial incisions along the nasal sidewall. Typically, a curvilinear incision is made midway between the nasion and the medial canthus. Incisions may be extended superiorly or laterally to address concomitant frontal sinus pathology.


Currently, ethmoid surgery is generally accomplished by endoscopic techniques, which offer superior visualization of anatomical detail compared with headlight surgery through a small incision.



Indications


Indications for the utilization of external ethmoidectomy include the following:




  • To address chronic inflammatory sinus disease involving the ethmoid and frontal sinuses



  • For anterior and posterior ethmoid artery ligation



  • For transethmoid approaches to the sphenoid sinus and sella



  • Drainage of subperiosteal or orbital abscess; an external approach is routinely faster than an endoscopic approach. Moreover, endoscopic approaches may be further complicated by difficulty in visualization and endoscopic dissection of the ethmoids in the setting of acute sinus infection



  • Orbital decompression



  • In the setting of benign tumors with extension from the ethmoids into the medial orbit (e.g., osteoma). By using an external incision, the surgeon is able to protect the orbital contents by directly visualizing and retracting the periorbita laterally, and subsequently dissecting medially through the lateral nasal wall and into the ethmoid air cells



  • External approaches have also been used to provide wider access to the anterior cranial base and cribriform region to address cerebrospinal fluid (CSF) leak repairs, dermoid excisions, meningoencephalocele repairs, and tumor (e.g., esthesioneuroblastoma) resections.8



Technique


External access to the ethmoid sinuses occurs via a curvilinear incision extending inferiorly from the medial end of the eyebrow, along the nasal sidewall midway between the medial palpebral line and the nasal dorsum. This incision usually heals well, leaving an inconspicuous scar. However, in some patients hypertrophy or webbing of the scar can occur. Gentle tissue handling and careful closure can minimize scarring. A zigzag or running “W-plasty” may be used to further camouflage the facial scar and may be particularly useful to prevent hypertrophic scarring in prone individuals. The angular vessels in this area are ligated with bipolar cauterization. The dissection should be extended down to the periosteum. Care must be taken to avoid injury to the supraorbital and supratrochlear neurovascular bundles that lie further laterally along the orbital rim. The periosteum is incised anterior to the anterior lacrimal crest, and it is elevated off the lacrimal bone. The medial canthal ligament should be elevated cleanly off the underlying bone. In doing so, the medial canthal ligament attachment remains intact and the lacrimal apparatus may be elevated out of its bony groove and retracted laterally with the orbit. The medial canthal ligament is returned to its native site at the conclusion of the procedure to restore aesthetic facial symmetry. The ligament is commonly fixed in placed with a nonabsorbable braided suture through a small drill hole made in the adjacent nasal bone and then through the ligament to reapproximate the proper position of the medial canthus.


During dissection further posteriorly, care must be taken to avoid damage to the trochlea of the superior oblique muscle, and the periosteum in this region must be elevated cleanly off the bone to avoid postoperative diplopia. Elevation further posteriorly reveals the lamina papyracea, frontoethmoidal suture line, anterior and posterior ethmoid arteries, and the optic nerve. The ethmoid air cells may be entered by traversing the lamina papyracea. The entire lamina, or the portion of the lamina required for appropriate exposure of the anterior and posterior ethmoid air cells based on the indication, may be removed. The importance of understanding the inferior slope of the ethmoid roof as one progresses further posteriorly warrants repeating. The surgeon must understand this anatomy and maintain orientation within the posterior orbit/ethmoids to avoid inadvertent entry into the intracranial cavity. During the entirety of the procedure, globe retraction should be gentle and released on occasion to prevent retinal ischemia.



Complications: Prevention and Management



Bleeding and Blindness

Bleeding from the superficial angular vessels may obscure visualization and cause difficulty during deeper dissection. Bipolar cautery should be used for optimal hemostatic control. Effective cauterization of these vessels will significantly minimize postoperative periorbital ecchymosis. Ligation with ties may result in postoperative subcutaneous thickening in this thin-skinned area. Similarly, ligation with clips should be avoided.


Bleeding from the anterior or posterior ethmoid arteries may result in significant retrobulbar hemorrhage, which may in turn result in vision loss. Knowledge of the location of these arteries may prevent injury. The anterior ethmoid artery is located within the frontoethmoidal suture line, 20 to 26 mm posterior to the anterior lacrimal crest. The posterior ethmoid artery is located ~ 10 to 12 mm posterior to the anterior ethmoid artery. The optic nerve is in close proximity to the posterior ethmoid artery (range: 2 to 8 mm posterior to the posterior ethmoid artery).21 Control of these arteries should occur via clipping or bipolar cauterization. Many surgeons will elect to ligate at least the anterior ethmoid artery prophylactically such that further manipulation will not inadvertently transect it, resulting in an orbital hematoma. It may be safer to prophylactically ligate this artery because the consequences of an intraorbital hematoma are substantial. The posterior ethmoid artery does not need to be routinely ligated unless further lateralization of the orbit is required for greater posterior exposure. Should the posterior ethmoid artery be ligated, extra care must be taken to avoid injury to the optic nerve, given the close proximity of the optic nerve immediately posterior to the posterior ethmoid artery.


Injury of either of the ethmoid arteries may be complicated by retraction of the vessel into the orbital fat and subsequent retrobulbar hemorrhage and hematoma formation. Rapid proptosis may occur with brisk retro-orbital bleeds. Less rapid bleeds may be heralded by signs such as lid edema, ecchymosis, proptosis, and an afferent pupillary defect. Intraoperatively, the eyes should be exposed so that these signs may be recognized early. Postoperatively, regardless of whether this occurs intraoperatively or postoperatively, blindness may result after a brief duration (60 to 90 minutes) of retinal ischemia. Ophthalmologic consultation should occur immediately.


If proptosis occurs intraoperatively, steps should be taken to normalize intraocular pressure. This may be serially monitored with an ocular tonometer. The periorbita may be incised to allow egress of the blood collecting in the retro-orbital space. If visible, the cut end of the artery should be identified and controlled with cautery or clips; however, if the cut end of the artery is not visible, further dissection into the orbital fat to visualize the severed artery is not advised, as it may lead to further orbital injury. Removal of any remaining lamina allows for decompression of the orbital contents into the nasal cavity, thereby reducing intraocular pressure.22


Proptosis may only become apparent postoperatively, either in the setting of an occult anterior or posterior ethmoid artery injury that progresses rapidly in the recovery room following an episode of coughing/straining, or over a protracted period of time as the result of a slowly progressing venous bleed. In all cases of suspected intraoperative disruption of the orbital blood supply, tight packing and postoperative nose blowing are prohibited. Careful postoperative monitoring for ecchymosis, firmness of the globe and a differential globe compressibility compared with the contralateral normal eye should be undertaken. Intraocular pressures of 40 mmHg and an afferent pupillary defect may occur. Arterial or venous bleeds leading to progressive increases in intraocular pressure and deterioration in vision represent surgical emergencies, and require a return to the operating room to surgically decompress the orbit (either as above or endoscopically). Several steps may be undertaken immediately while awaiting assessment by ophthalmology and/or return to the operating theater (see Chapter 9, Figure 9.22 for the emergency management of orbital hematoma). Any ipsilateral nasal packing left in place should be removed. Lateral canthotomy (cutting laterally from the lateral lid commissure; the endpoint is the lateral orbital rim) and inferior cantholysis can be performed rapidly at the bedside to allow expansion of the orbital contents anteriorly and a return of blood flow. The inferior tarsal plate may be identified and divided sharply. A small portion of tarsus should be left laterally to allow subsequent reapposition following resolution of this emergency situation.


The optic nerve is prone to injury during dissection within a posteriormost ethmoid air cell that pneumatizes around the optic nerve (the Onodi cell). In this situation, lateral dissection within this ethmoid air cell may result in optic nerve injury and resultant visual dysfunction or blindness. Optic nerve injury results in decreased visual acuity and visual field defects. Guidelines for the optimal management of optic nerve trauma are lacking. The use of high doses of intravenous steroids remains controversial. When optic nerve injury is confirmed, common protocols suggest the administration of intravenous dexamethasone with an initial loading dose of 1 mg/kg followed by 0.5 mg/kg every 6 hours thereafter.23 If vision improves, therapy is continued for a further 5 days. If vision fails to improve within 36 hours, or initially improves but then deteriorates, optic nerve decompression should be considered. However, in the International Optic Nerve Trauma Study, a comparative interventional study of 133 patients, investigators failed to demonstrate a difference in outcomes when comparing steroid therapy, surgical optic nerve decompression, and observation in patients with traumatic optic neuropathy.24 They concluded that neither steroids nor surgical decompression should be considered the standard of care and that, in many cases, no intervention may suffice as management of a terminal traumatized optic nerve.


Significant lateral retraction of the orbital contents to improve visualization may also result in impaired blood flow to the retina and other orbital structures. Delicate and careful retraction, with frequent removal of retraction pressure, is recommended to facilitate blood flow to the orbit.

Injury to the right medial rectus muscle and subsequent alteration in eye movements.

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Jun 29, 2020 | Posted by in OTOLARYNGOLOGY | Comments Off on External Approaches to the Paranasal Sinuses and Skull Base
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