Introduction

This chapter describes the anatomy of the sphenopalatine and internal maxillary arteries in detail to provide a framework for the surgical management of these regions. Techniques for the endonasal endoscopic approach to the sphenopalatine artery (SPA) are discussed. Approaches to the maxillary artery within the pterygopalatine fossa are also discussed including the transantral approach. Complications of these approaches as well as tips and pitfalls are also highlighted.

8.1 Anatomy of the Sphenopalatine and Maxillary Arteries

8.1.1 Maxillary Artery

The maxillary artery is one of two large terminal branches of the external carotid artery and arises deep to or within the parotid gland, below the level of the temporomandibular joint. It then passes horizontally between the sphenomandibular ligament and the ramus of the mandible to cross the lower head of the lateral pterygoid muscle where it is embedded within the pterygoid venous plexus. Next it enters the pterygomaxillary fissure and runs posterior to the posterior wall of the maxillary sinus and terminates by entering the nasal cavity as the SPA via the sphenopalatine foramen ( Fig. 8.1 ).

The maxillary artery is typically described as having three parts based on its relationship to the lateral pterygoid muscle. The first part lies medial to the mandible and lateral to the lateral pterygoid muscle and typically has four branches. The second part is the portion crossing the lateral pterygoid muscle and typically has six muscular branches and a variable relationship to that muscle. The third portion of the maxillary artery is the part of most interest to the rhinologist. It enters the pterygopalatine fossa via the pterygomaxillary fissure. Within the pterygopalatine fossa, the artery runs a torturous course and gives off several branches, coming to an end as it exits the sphenopalatine foramen as the SPA.1 Choi and Park2 demonstrated five arteries arising from the third part of the maxillary artery commencing at a level of one-third the height of the posterior maxillary wall. These were the posterior superior alveolar, infraorbital, pterygoid canal, descending palatine, and sphenopalatine arteries, with their origins occurring in this order from lateral to medial in 85% of cases.

The third part of the maxillary artery passes in an anteromedial superior direction upon entering the pterygopalatine fossa ( Fig. 8.2 ). Within the pterygopalatine fossa, the course of the maxillary artery can be described as looped (most common), bifurcated, or straight. As the maxillary artery traverses the pterygopalatine fossa, it is always located anterior to the neural elements, and the terminal division occurs in the medial superior third in 60% of cases and the middle medial third in 30% of cases, with occasional divisions elsewhere within the pterygopalatine fossa. The configuration of the terminal branches of the maxillary artery is also quite variable and can take several different formats, also previously described by Choi and Park.2 While these descriptions are a helpful aid, it is difficult to predict the individual variation that will be encountered in any particular case; hence, it is incumbent upon the surgeon to expect wide variation in the course of the maxillary artery and its branches and to operate in such a manner as to account for possible variations.

8.1.2 Sphenopalatine Artery

The SPA is the terminal branch of the maxillary artery and supplies the mucosa of the nasal septum and lateral nasal wall. It enters the nasal cavity via the sphenopalatine foramen ( Fig. 8.3 ) and divides into posterior lateral nasal and posterior nasal arteries. The larger of the branches is the posterior lateral nasal branch, which goes on to supply the middle and inferior turbinates. The posterior nasal branch crosses the anterior face of the sphenoid sinus below the level of the sphenoid ostium before dividing into branches on the septum.1 It is the vessel commonly encountered during endoscopic sinus surgery as the surgeon opens the sphenoid sinus inferiorly and is the critical vascular supply for the nasoseptal flap.

The sphenopalatine foramen is located on the lateral wall of the nose at the level of or within 10 mm of the posterior wall of the maxillary sinus.3 It is bounded superiorly by the body of the sphenoid bone, while the palatine bone forms the anterior, posterior, and inferior borders via its orbital process, perpendicular plate, and sphenoidal processes, respectively. The crista ethmoidalis ( Fig. 8.3 ) is a reliable lateral nasal wall landmark for the SPA and is formed by a small bony crest of the perpendicular plate or ascending process of the palatine bone that meets the most posterior, inferior, and lateral aspect of the middle turbinate.4 It typically lies immediately anterior to the anteroinferior aspect of the sphenopalatine foramen and on occasion is directly inferior. It can be used as a landmark for SPA ligation. Wareing et al.5 demonstrated that the location of the sphenopalatine foramen can be within the middle meatus, superior meatus, or transition region between the two.

The sphenopalatine foramen is approximately 6 mm in vertical dimension and often takes an hourglasstype shape.3 Accessory sphenopalatine ostia have been demonstrated to be present in 10 to 13% of cases by several authors.6,7 Accessory foramina are typically located anterior and inferior to the true foramen.5

Within the sphenopalatine foramen, the SPA divides into its branches in 80% of cases prior to the passage of the vessel into the nasal cavity.6 Consequently, there are often multiple branches emanating from the foramen at its entry point into the nasal cavity. Simmen et al8 have demonstrated that 97% of specimens had two or more branches and 64% had three or more. Typically, there are two major branches. This is a key observation, as successful ligation of the SPA at the foramen typically requires multiple branches to be addressed. Failure to do so is proposed to be a significant reason for failed management of posterior epistaxis via endoscopic SPA ligation.9

8.2 Indications for Approaches to the Sphenopalatine and Maxillary Arteries

There are several indications for utilizing direct surgical approaches to the sphenopalatine and maxillary arteries. These indications include:

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  Posterior or refractory epistaxis.

  
  
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  Surgery for benign and malignant neoplasms of the paranasal sinuses, nasal cavity, and pterygopalatine fossa.

  
  
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  As part of the initial approach to the vidian nerve in the pterygoid canal.

Furthermore, approaches toward the sphenopalatine and maxillary arteries may form an important part of several extended endoscopic endonasal approaches involving the following sites:

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  Lateral recess of the sphenoid sinus.

  
  
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  Cavernous sinus and middle cranial fossa.

  
  
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  Pterygopalatine and infratemporal fossa.

  
  
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  Posterior cranial fossa.

  
  
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  Petrous temporal bone.

The choice of approach is largely dictated by the particular pathology, its anatomic extent, and the fundamental need of the surgeon to have adequate exposure to operate safely and efficiently.

8.3 Surgical Approach to the Sphenopalatine Artery

The SPA is typically approached under a general anesthesia. In occasional instances where a patient is not fit for general anesthesia, the approach may be conducted under local anesthetic.

In both instances, the nose is prepared with injection of local anesthetic with adrenaline, in particular addressing the mucosa in the surgical field located above the inferior turbinate within the middle meatus. Topical vasoconstrictor (if possible, cocaine < 3 mg/kg with adrenaline 1:10,000) is also applied via cottonoids to the mucosa within the surgical field and along the operative channels (nasal septum and inferior turbinates). Preparation of the nose in this manner prior to the surgical scrub allows the full benefits of the topical and injected agents to be realized and hence the patience of the surgeon is rewarded with an improved surgical field. In instances where there is temporary nasal packing in place maintaining hemostasis, the surgeon may elect to perform the preparation of the nose once all equipment is prepared and the surgeon has performed a surgical scrub and established a sterile surgical field.

Once the surgical scrub has been completed and a sterile surgical field established, the surgeon may elect to infiltrate additional local anesthetic with adrenaline via the greater palatine canal, as described by Douglas and Wormald.10 This can enhance the surgical field by inducing vasoconstriction of the SPA and may be of particular benefit in the management of posterior epistaxis and those patients with an ongoing anticoagulant need. To perform this infiltration, the surgeon places his or her finger into the mouth and palpates the hard palate in the region of the second upper molar tooth. A depression should be felt indicating the entry point to the canal. Using an endoscope, the surgeon can identify the position of the foramen visually and maintain this visualization for introduction of the needle. A 25-G needle, bent to 45 degrees at 25 mm from the tip of the needle, is introduced into the foramen at the previously identified position and then advanced to the point of the bend. At this point, 2 mL of local anesthetic with adrenaline is infiltrated. Often, but not always, the ipsilateral hard palate mucosa will be seen to blanch following the injection, which is a reassuring indication of correct placement.

At the commencement of the procedure, a septoplasty may be needed in some instances to access the middle meatus, and this should be performed before any procedure upon the SPA is begun. Once the middle meatus is easily accessible, the endoscope is passed into the middle meatus, and the posterior fontanelle of the lateral nasal wall is identified as an anterior landmark for surgery via palpation of the lateral nasal wall within the middle meatus. The posterior fontanelle is a site within the wall separating the maxillary sinus and nasal cavity where the mucosa is intact but the bone deficient. A vertical incision is then made with a no. 15 blade scalpel on a 7 BP handle just posterior to the fontanelle onto the palatine bone from the upper part of the middle meatus and carried down to the level of the inferior turbinate insertion. Horizontal incisions are made at the top and bottom of this incision to allow the elevation of a posteriorly based nasal mucosal flap ( Fig. 8.4 ). A suction Freer elevator is used to elevate this flap. Malleable instrumentation can be an advantage at this stage if available. It is important to ensure the surgeon is directly dissecting onto the bone, as dissection in this surgical plane greatly simplifies the procedure. Dissection should be commenced at the inferior aspect of the flap and gradually elevated posteriorly and superiorly.

As the dissection progresses, the crista ethmoidalis will be approached just anterior to the sphenopalatine foramen. This can be easily removed with a Hajek-Koffler punch or similar instrument, being careful not to damage the sphenopalatine neurovascular bundle. To avoid this problem, ensure that the instrument is firmly engaged upon the bone prior to removal of the crest. Upon closure of the instrument, be sure to fully release the instrument from the dissected bone. This permits the release of the artery if inadvertently captured in the device and significantly reduces the risk of avulsion or tear to the vessel as can be seen when the instrument is engaged and then directly removed from the nasal cavity. Bone fragments noted after release can be removed at this point via a simple grasping instrument.

Immediately posterior to the crest, the SPA will be enco untered as it exits the sphenopalatine foramen. At this site, it should be carefully isolated from the surrounding connective tissue. A sickle knife or suction Freer is commonly employed for this task. Once identified along a suitable length, it is our practice to use suction bipolar forceps to diathermize the vessel. The vessel is then divided, and dissection continues posteriorly and superiorly to identify further branches of the SPA and importantly the posterior nasal artery ( Fig. 8.5 and 8.6 ). As they are encountered, these vessels are coagulated with bipolar electrocautery and divided. At the conclusion of the dissection, the divided vessel stumps will be discernable on the lateral nasal wall and the lateral aspect of the anterior face of the sphenoid clean and visible at the posterior aspect of the dissection. In some instances, vascular clips may be utilized to aid hemostasis. It is our preference to use bipolar cautery in all instances, including when clips are utilized, as inadequately placed clips can become dislodged and lead to bleeding intraoperatively or postoperatively.

The mucosal flap is then replaced and a small piece of Surgicel placed over the flap to maintain its position. The patient is usually able to be discharged 12 to 24 hours postprocedure and is sent home on 6 hourly nasal saline douches and with a 5- to 10-day course of oral antibiotics.

Related posts:

Chapter 4 Frontal Sinus and Draf Approaches Chapter 5 Sphenoid Sinus Chapter 6 Medial Maxillectomy Chapter 3 Endoscopic Lateral Nasal Wall and Anterior and Posterior Ethmoid Sinus Dissection Chapter 7 Anterior and Posterior Ethmoidal Arteries Chapter 28 Retrosigmoid–Transclival Approach

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