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Figure 45 Sagittal (a) and endoscopic (b) views with the lacrimal sac and duct marsupialized by completely removing the medial bony and membranous wall. S = lacrimal sac. D = lacrimal duct. MT = middle turbinate. IT = inferior turbinate.

Sphenoid Sinus Abscess

Figure 46

Sagittal (a) and endoscopic (b) views after removing an anterior segment of inferior turbinate to expose the entire course of the nasolacrimal duct. Small arrows denote the resected edges of the inferior lacrimal sac and duct. Probe illustrates Hasner's valve (H). MT = middle turbinate. IT = inferior turbinate. IM = inferior meatus.

Middle Turbinate Visual
Figure 47

Sagittal view illustrating a patulous opening and absent Hasner's valve. A patulous opening is encountered superiorly in the inferior meatus in some cases. Small arrows illustrate the membranous canal leading up to the nasolacrimal opening. IT = inferior turbinate.

D. Orbital Decompression (Figures 48-50)

Orbital decompression may be indicated for a patient with an orbital abscess, periorbital or orbital hematoma, or severe Graves' ophthalmopathy with exposure keratitis and threatened visual loss (69-79). When a subperiosteal abscess is present, only the lamina papyracea needs partial or complete removal to ensure adequate drainage of the abscess loculations into the nose. This may require exposing the periorbita over the superomedial or inferomedial orbital walls to ensure adequate drainage of all potential abscess loculations. Nasal packing is usually avoided. The peri-orbita is left intact.

For patients with Graves' ophthalmopathy, the lamina papyracea and MOF are removed medial to the infraorbital nerve through a wide antrostomy. Postoperative diplopia is possible, but may be minimized by preserving the horizontal ridge of the antrostomy (80). The periorbita is incised to allow herniation of orbital fat into the ethmoid and maxillary sinus cavities. The latter generally allows for approximately 4-5 mm of orbital decompression. This may have to be combined with a lateral orbital decompression through an external approach. Care is taken not to occlude the maxillary, frontal, or sphenoid ostia with orbital fat, as this may result in secondary ostial obstruction and rhinosinusitis (81,82). In these situations an extended middle meatal, frontal, and/or sphenoid sinusotomy may be prudent.

Figure 48 Endoscopic view showing careful elevation and piecemeal removal of lamina papyracea (arrows) away from the periorbita (P). Periorbital abscesses and hematomas occur in this space.

Figure 49 Sagittal (a) and endoscopic (b) views denoting longitudinal incisions for orbital fat decompression as performed for Graves' ophthalmopathy.

Figure 49 Sagittal (a) and endoscopic (b) views denoting longitudinal incisions for orbital fat decompression as performed for Graves' ophthalmopathy.

Sphenoid Sinusosopy
Figure 50 Endoscopic view with orbital fat extending into the ethmoid cavity.

E. Optic Nerve Decompression and the Carotid Artery (Figure 51)

In patients with worsening visual acuity due to traumatic neuropathy or neoplastic compression, an optic nerve decompression may be indicated (83-86). The orbital apex may be found by following a line from the superior vertical ridge of the antrostomy to the roof of the posterior ethmoid sinus adjacent to the orbital wall. It is located at the same level as the posterior wall of the maxillary sinus in the coronal plane, and approximately 7 cm from the columnella. The canalicular portion of the optic nerve is identified as it takes an abrupt turn medially at this point as it courses toward the optic chiasm. The thicker bone in this area is carefully thinned with a diamond bur and removed with a periosteal elevator. In the laboratory this can be carefully performed utilizing a bone curette. The length of the canalicular portion is approximately 8-12 mm. The optic nerve sheath is continuous with the dura mater in this area. Incision of this thick sheath reveals the optic nerve. The space around the nerve is continuous with the subdural space and results in a CSF leak if left open to the nasal cavity. Therefore, if the optic nerve sheath is opened, one must be prepared to close the CSF leak with a small mucoperichondrial graft.

The intrasphenoid carotid artery runs in a posteroinferior to anterosuperior direction, giving it the appearance of an inverted S. Its most anterior (cavernous) segment runs immediately inferior to the canalicular portion of the optic nerve as it courses intracranially, creating a small triangular recess (opticocarotid recess). In some patients with a well-pneumatized sphenoid, the carotid projects into the lumen of the sphenoid and is prone to inadvertent injury if one enters too far laterally through the posterior wall of the posterior ethmoid sinus. For this reason the sphenoid is generally entered medially adjacent to the septum, as previously described.

Figure 51 Sagittal (a) and endoscopic (b) views showing the canalicular portion of the optic nerve (ON) and intrasphenoid carotid artery (CA) after bone removal. Asterisks denotes the opticocarotid recess. The area of the anulus of Zinn (dotted oval) and the antrostomy ridge (small arrows) are shown.

Figure 51 Sagittal (a) and endoscopic (b) views showing the canalicular portion of the optic nerve (ON) and intrasphenoid carotid artery (CA) after bone removal. Asterisks denotes the opticocarotid recess. The area of the anulus of Zinn (dotted oval) and the antrostomy ridge (small arrows) are shown.

Opticicocarotid Recess

F. Orbital Dissection (Figures 52 and 53)

Removal of the periorbita and fat reveals the medial rectus muscle coursing along the medial wall of the orbit. The medial aspects of the inferior rectus muscle may be seen running adjacent to the horizontal ridge of the antrostomy. Further removal of fat between the two muscles reveals the orbital segment of the optic nerve and globe. The anulus of Zinn, representing the thick fibrotic insertion point for all the extraocular muscles, can be identified after removing bone at the orbital apex. By longitudinally transecting the anulus of Zinn, between the medial and inferior rectus muscles, one can expose the entire course of the intraorbital and canalicular segments of the optic nerve.

Figure 52 Sagittal (a) and endoscopic (b) views after removal of the periorbita and fat, showing the medial rectus muscle (MR), inferior rectus muscle (IR), and globe (G). The anulus of Zinn is circled. The optic nerve sheath has been opened to reveal the canalicular portion of the optic nerve (O). C = intrasphenoid carotid artery.

Figure 52 Sagittal (a) and endoscopic (b) views after removal of the periorbita and fat, showing the medial rectus muscle (MR), inferior rectus muscle (IR), and globe (G). The anulus of Zinn is circled. The optic nerve sheath has been opened to reveal the canalicular portion of the optic nerve (O). C = intrasphenoid carotid artery.

Canalicular Segment Optic Nerve
Figure 53 Sagittal view after transection of the anulus of Zinn, revealing the orbital (small arrows) and canalicular (large arrows) segments of the optic nerve.

G. Extended Frontal Sinusotomy and the Lothrop Procedure (Figures 54-57)

An extended frontal sinusotomy may be indicated in select cases with chronic frontal rhino-sinusitis refractory to medical and/or more traditional endoscopic surgical management (87-90). After identifying the superior aspect of the lamina papyracea and anterior ethmoid roof, the approximate coronal level of the posterior frontal sinus wall is determined on at least one side. This may be accomplished either directly through the natural frontal ostium area or through a transeptal approach bypassing this area altogether (91). A 30- or 70-degree telescope looking superiorly is used.

The mucosa on the posterior wall of the frontal recess area is preserved whenever possible. However, in many cases this is not possible because of the significant amount of fibrosis and/or osteoneogenesis in the area. The perpendicular plate of the ethmoid is conservatively resected with cutting forceps anterior to the coronal plane of the posterior wall of the frontal sinus as seen through the frontal sinus ostium or through a transeptal frontal sinusotomy. Posterior to this plane, the potential is increased for inadvertent intracranial penetration, or injury to the cribriform plate and olfactory fibers. An imaginary horizontal line is maintained (in the coronal plane) across the posterior wall of the frontal sinus at all times. The perpendicular plate and intersinus septum of the frontal sinus is followed superiorly, anterior to this line, working simultaneously from both sides of the nose. The perpendicular plate is resected posterior to the nasal bones, and followed superiorly toward the intersinus septum. The dense bone at the nasofrontal area is removed with cervical spine bone curettes, cutting forceps, and/or frontal rasps, until the posterior table of the frontal sinus is clearly visualized. Once the common frontal sinus ostium is visualized, further enlargement can be performed with powered instrumentation.

Occasionally, one or more intersinus cells within the frontal sinus intersinus septum have to be completely removed to create the common frontal ostium. The final common frontal sinusotomy opening is horseshoe-shaped, measuring approximately 8 x 24 mm in the anteroposterior and lateral dimension, respectively (89). The posterior, lateral, and anterior walls of the common ostium are made up of the posterior wall of the frontal sinus, lamina papyracea, and anterior wall of the frontal sinus at the nasion area, respectively. The final ostium should allow for complete transillumination and visualization of the full extent of the frontal sinus, including its lateral recesses. If closer examination of the frontal sinus is warranted, a flexible fiberoptic nasopharyngoscope may be inserted through the common frontal ostium.

Frontal Ostium

Figure 54 Sagittal (a) and endoscopic (b) views denoting the degree of perpendicular plate removal (circle) for an endoscopic Lothrop procedure. Care is taken not to extend the septal resection margins too far posteriorly to minimize the chance of inadvertent injury to the olfactory apparatus or intracranial penetration. Small arrows show the area of the olfactory bulb and cribriform plate. A frontal intersinus cell (F) is frequently encountered. The dotted line shows the trajectory for a transeptal penetration into the frontal sinus. CG = crista galli. MT = middle turbinate. NS = nasal septum.

Figure 54 Sagittal (a) and endoscopic (b) views denoting the degree of perpendicular plate removal (circle) for an endoscopic Lothrop procedure. Care is taken not to extend the septal resection margins too far posteriorly to minimize the chance of inadvertent injury to the olfactory apparatus or intracranial penetration. Small arrows show the area of the olfactory bulb and cribriform plate. A frontal intersinus cell (F) is frequently encountered. The dotted line shows the trajectory for a transeptal penetration into the frontal sinus. CG = crista galli. MT = middle turbinate. NS = nasal septum.

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