Preoperative Management

To obtain optimum information about a paranasal sinus or skull base pathology, we recommend both preoperative high-resolution computed tomography (CT) and magnetic resonance imaging (MRI). CT is superior in determining osseous involvement, as it provides information about areas of bone erosion, expansion, or bowing. MRI will help in determining endocranial extension of the disease. MRI also can help differentiate neoplasia from polyps, inflammation, and secretions ( Fig. 42.1 ). The former pathologic conditions present a low to intermediate intensity signal on T2-weighted images, whereas the latter present high-intensity images. Further imaging is used to exclude local or distant metastases in the staging of disease ( Fig. 42.2 ).

CT and MRI can be fused for intraoperative navigation through bony and parenchymal windows. Image fusion is used to confirm the visual impression of the surgical anatomy, notably critical neurovascular structures, thereby facilitating a targeted resection. Intraoperative CT can be performed if necessary to update the image guidance system throughout surgery. The vascularity of a lesion can be evaluated with either CT angiography, MR angiography, or digital subtraction angiography. If the tumor has reached or involved the internal carotid artery, a balloon occlusion test should be performed together with a perfusion scintigraphy of the brain. In cases of a suspected cerebrospinal fluid (CSF) leak, CT or MR cisternography might be a helpful investigation.

Depending on the lesion′s pathology, location, and extension, the presence of cranial neuropathies should be addressed prior to surgery by a neurologist and ophthalmologist. Endoscopic evaluation should be performed with local anesthetic, although in cases of limited access to the lesion and when difficulty in controlling hemorrhage is expected, biopsies should be undertaken using general anesthesia. Additional care must be taken to inspect the area beyond the lesion, to confirm the extent of the disease ( Fig. 42.3 ).

Anesthesia and Patient Positioning

All procedures are performed under general anesthesia; the key point for the anesthetist is to reduce cardiac output primarily by ensuring bradycardia. The patient is positioned supine at 20 degrees body up to reduce the venous pressure. The head can be fixed in a Mayfield holder. This reduces intraoperative movement, especially during drilling and neurovascular dissection, but is not mandatory. In many of our cases, the patient′s head rests freely in a horseshoe head holder and is reclined and angled ~20 degrees toward the right shoulder. This arrangement allows the surgeon to stand or sit comfortably on the patient′s right side and gives enough space to work from caudally. We prefer to operate from a live screen that is positioned opposite the surgeon at a level just above the plane of the surgeon′s visual axis. If a four-hand technique is needed (i.e., two surgeons are working), then both are standing or sitting at the right side of the patient′s head, with the video screen positioned opposite them. The anesthetist sits at the left foot, and the surgical assistant stands at the right foot of the table.

We routinely use frameless stereotactic image guidance, which is ideally positioned directly beside the video screen. We advocate neurophysiologic monitoring, including cortical function (somatosensory evoked potentials) with or without brainstem function (brainstem evoked responses), for cases that will require intradural surgery or dissection near the circle of Willis or internal carotid arteries. When dissection of cranial nerves is predicted based on tumor anatomy, cranial nerve electromyography is also performed.

After optimal positioning, the skin of the external nose and nasal vestibule, as well as the abdomen or hip (fat graft or fascia lata site, respectively, if potentially needed), is prepped with an iodine antiseptic solution. For vasoconstriction, we use ribbon gauze soaked with xylometazoline, which is placed in the nasal airway and the middle meatus. For local anesthesia, we inject lidocaine 1% with adrenaline 1:200,000. Perioperative wide-spectrum antibiotic prophylaxis is administered (usually a cephalosporin).

Indications

• 
  

  Benign tumors (e.g., inverted papilloma, juvenile angiofibroma, osteoma)

  
  
• 
  

  Malignant tumors

Contraindications

• 
  

  Tumor infiltration of the orbit

  
  
• 
  

  Far lateral tumor extension to the frontal sinus and/or lateral infratemporal fossa

  
  
• 
  

  Massive involvement of the skull base

  
  
• 
  

  Encasement of the internal carotid artery

  
  
• 
  

  Previously treated patients (e.g., with radiotherapy)

Surgical Steps

There are two main principles in endonasal tumor surgery: 1) to dissect around the tumor from all sides (from lateral, caudal, and cranial) along normal anatomical structures resulting in an “in toto” tumor resection and 2) to debulk (i.e., piecemeal multilayer tumor removal from the center to the periphery so that the tumor collapses, the borders will become visible, and the tumor can be resected along them with an adequate safety margin) ( Fig. 42.4 ). Radical extirpation of the disease does not depend on en bloc resection as shown by our long-term results of inverted papilloma and malignant tumors.5,6 Instead, the primary purpose is to identify and widely remove the tumor origin as well as the infiltrated structures, i.e. anterior skull base, dura, or lamina papyracea. It is acceptable, therefore, to resect larger tumors segmentally.5,7–12

We usually start anteriorly with a frontal sinus drainage type III according to Draf,13 then resect the upper nasal septum and explore the anterior skull base, dissecting the tumor down to the sphenoid sinus. If necessary, this includes the removal of the cribriform plate, the crista galli, and the surrounding dura. Laterally, the margin of dissection is the periorbit and medially usually the nasal septum or the opposite nasal cavity, and in large lesions the opposite periorbit. In the case of periorbital infiltration, the periorbit can be removed and reconstructed with Tutoplast fascia lata (Tutogen Medical Co., Neunkirchen am Brand, Germany). Duraplasty is generally performed as described by Schick et al.14

In some circumstances, it will be necessary to combine the endonasal approach with an external procedure (i.e., a midfacial degloving or a subcranial approach according to Raveh et al15) to achieve clear margins. Then, the surgeon must have the expertise to proceed. In cases of expected incomplete tumor removal (tumor infiltrating the internal carotid artery, the optic nerve, or the cavernous sinus, i.e., in adenoid cystic carcinoma or in metastases), endonasal palliative surgery may be indicated, not with curative intent but as an attempt to achieve considerable improvement in quality of life. Finally, it is important to recognize when endonasal resection is not in the patient′s best interests (e.g., tumor infiltration of the frontal lobe or the cavernous sinus, although benign tumors involving the cavernous sinus can often be addressed endonasally).

For more details, see Chapter 43.

General Remarks on Anatomical Considerations

The infraorbital nerve (maxillary division of the fifth cranial nerve) exits the infraorbital foramen just below the inferior orbital rim and innervates the skin of the cheek, upper lip, lateral nose, and gingiva ( Fig. 42.5 ).

The superior maxillary wall is the floor of the orbit, and the inferior wall is the palatine bone, which forms the hard palate with the contralateral wall. The medial maxillary wall, including the respective inferior and middle turbinates and the ethmoid sinuses, forms the lateral nasal wall. Care must be taken, as the nasolacrimal apparatus lies just anterior to this. The inferior nasal cavity wall is formed by the palatine bone.

The angular vein is located close to the medial canthus and the nasofacial junction. The anterior and posterior ethmoidal arteries lie within the frontoethmoidal suture line. The anterior ethmoidal artery lies in average 24 mm posterior to the lacrimal crest. The posterior ethmoidal artery lies ~12 mm behind the anterior ethmoidal artery, and the optic nerve lies 6 mm farther posteriorly and therefore can easily be damaged. (24–12–6 mnemonic rule). The anterior cranial fossa lies immediately above the level of the frontoethmoidal suture line.

Mobilization of the maxillary bone should take into consideration its attachments to the facial skeleton:

1. 
   

   Superiorly, the frontal process is connected to the frontal and nasal bones.

   
   
2. 
   

   Laterally, the zygomatic process is connected to the zygomatic bone.

   
   
3. 
   

   Inferiorly, the alveolar ridge to the contralateral wall anteriorly, the palatine bone to the contralateral wall medially, and the maxillary tuberosity to the pterygoid plates posteriorly.

Lateral Rhinotomy with Medial Maxillectomy

Contraindications

Large tumors, with an extension beyond the lateral wall of the nasal cavity (invasion of the cribriform plate, ethmoidal roof, sphenoid sinus, or floor of the nose) cannot be removed fully via this approach and therefore may require more extensive procedures.

Surgical Steps

An oral endotracheal tube is placed and fixed contralateral to the lesion ( Figs. 42.6 , 42.7 , and 42.8 ). The patient is placed in a reverse Trendelenburg position, and the head is slightly rotated contralateral to the affected side. Subsequently, appropriate vasoconstriction of the nasal cavity is performed. Next, the patient is scrubbed and draped, and an ipsilateral tarsorrhaphy is performed. As mentioned previously, detailed assessment of the lesion and its extent is necessary prior to starting the procedure.

The incision starts at the philtrum, close to the columella, and continues around the nasal vestibule and ala, entering the nasolabial crease and extending superiorly along the nasofacial junction. The superior end varies according to the extent of the disease, reaching up to the midpoint between the medial canthus and the nasal dorsum. The incision is designed so that it is medial to the attachment of the medial canthal ligament. Careful cross-hatching of the incision is mandatory to achieve accurate wound closure.16–18

If further access is needed, the original incision can be extended as follows:

1. 
   

   Extending from the columella down the middle to the upper lip (Weber-Ferguson incision)

   
   
2. 
   

   From the superior end at the level of the medial canthus to the medial edge of the eyebrow (Lynch extension)

   
   
3. 
   

   From the superior end at the level of the medial canthus along the lower eyelid to the lateral canthus (subciliary extension)

Throughout the procedure, traction is applied to provide wide access; inferiorly, sharp retractors can be used to great effect to reflect the nasal ala contralaterally, offering access to the anterior nasal cavity. Care, however, must be taken in the orbital region, because the skin, fascia, orbital contents, and infraorbital nerve can be easily damaged. In these cases, malleable or orbital retractors should be used.

During the procedure, hemostasis is maintained with bipolar diathermy, hemostats, and ties. The angular vein is a common source of bleeding during the initial stages of the procedure, which needs to be controlled accordingly. Care should also be taken to ligate the anterior ethmoidal artery if a maxillectomy is performed. The posterior ethmoidal artery should be preserved as the posterior margin of the dissection. Bleeding is also encountered at the final stages of the procedure from branches of the internal maxillary artery.

The incision is brought down to bone, and the periosteum is elevated from the maxilla and frontal process.

In cases of small anterior septal lesions, the dissection continues to gain access into the nasal cavity. By dividing the vestibular mucosa, the nasal cavity is accessible, and with the use of appropriate traction, the area of interest is visualized directly. The lesion is removed with a surrounding cuff of mucosa and the underlying cartilage, while the contralateral septal mucosa is maintained intact.

In cases of larger lesions of the lateral nasal wall, osteotomies are performed to enable a medial maxillectomy. Initial dissection is performed on a wider front and continues laterally. Superiorly, the extension of the periosteal elevation reaches the medial orbital rim, at which point the medial canthal ligament is detached from the lacrimal fossa crests. If the ligament is transected, it should be tagged so that it can be repositioned during closure. Next, the lacrimal sac is mobilized from its fossa and reflected superiorly. Elevation of the periorbita continues, and the eye is gently mobilized laterally. Following these manipulations, the frontoethmoidal suture line, anterior ethmoidal artery, and 12 mm deeper, posterior ethmoidal artery are identified; the latter being the posterior margin of the osteotomies. Extra care must be taken during these maneuvers, as the optic nerve lies ~6 mm farther posteriorly and therefore is at risk. As the anterior cranial fossa is located above the frontoethmoidal suture line, this landmark is the superior dissection margin.

Elevation of the maxillary periosteum continues laterally until the infraorbital foramen, which is the lateral margin of dissection.

The following osteotomies are performed to mobilize the lateral nasal wall specimen (see Fig. 42.7a ):

1. 
   

   The nasal pyramid is separated from the frontal process with a lateral osteotomy. The attached nasal soft tissues and the bone are reflected toward the other side, providing improved access.

   
   
2. 
   

   The anterior antral wall is entered via an opening created at the canine fossa, which is gradually enlarged to confirm that the disease has not extended beyond the lateral nasal wall.

   
   
3. 
   

   A further osteotomy is performed inferiorly across the piriform rim, reaching the inferior meatus, which is extended backward under the inferior turbinate attachment.

   
   
4. 
   

   Another osteotomy is made from the antrum opening, upward toward the inferior orbital rim, staying medially to the infraorbital foramen.

   
   
5. 
   

   A further oblique cut is performed just in front of the pterygoid plates.

   
   
6. 
   

   A cut is performed along the frontoethmoidal suture line. Care needs to be taken to avoid entering the anterior cranial fossa, which lies just above this level, and to preserve the posterior ethmoidal artery, which is the posterior margin.

   
   
7. 
   

   A further anterior cut just above the lacrimal fossa releases the specimen from the frontal maxillary process.

   
   
8. 
   

   A final posterior cut is made from the level of the posterior ethmoidal artery toward the infraorbital rim section.

The specimen is delivered en bloc, with a rocking motion. Any further bleeding is arrested accordingly, with ligation, cautery, or packing. A nasal pack is usually inserted and left in place for the next few days.

Closure should be performed with care to avoid unwanted postoperative deformities. Special care needs to be taken with the exact repositioning of the medial canthal ligament, which should be resutured to the periosteum or attached through a hole opened with a drill to the nasal bone. After the tarsorrhaphies are removed, both the superior and inferior canaliculi can be stented with Silastic tubes to avoid stenosis and subsequent epiphora. Appropriate eye care is applied (i.e., eye ointment, eye pad).

Broad-spectrum antibiotics are prescribed for the next few days.

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