Approaches to the Ethmoid and Sphenoid Sinuses

For external ethmoidectomy/sphenoidotomy indications are:

Chronic ethmoid sinusitis unresponsive to conservative intranasal procedures. As an approach to the orbital apex for optic nerve decompression.

As an approach to the anterior skull base or sphenoid sinus in the treatment of CSF rhinor rhea or other abnormality, such as encephalo-cele.

As an approach to the lacrimal sac for dacryo-cystorhinostomy.

As an approach to the anterior and posterior ethmoid arteries in the treatment of refractory epistaxis.

No true ethmoidectomy is necessary, just the exploration of the medial orbital wall. For the treatment of acute complicated ethmoid sinusitis.

Orbital abscess or subperiosteal abscess.

The external ethmoidectomy approach is a classic approach that has been used to address a large variety of conditions, including acute and chronic infection of the ethmoid and sphenoid sinus; as an approach to infections of the orbit; as an approach to the cribriform and fovea ethmoidalis in the treatment of CSF fistulae and defects of the anterior skull base; as an approach to the anterior and posterior ethmoid arteries in the treatment of recalcitrant epistaxis; and as a portion of several larger operations, such as approaches to the

Trephination
Fig. 22.2. Incisions for external ethmoidectomy and frontal sinus trephination

nasofrontal drainage system, maxillectomy and craniofacial resection.

Prior to beginning an external ethmoidectomy, the nasal cavity is packed with cottonoid pledgets that have been impregnated with vasoconstrictor. The external ethmoidectomy is performed via a gull-wing incision centered midway between the medial canthus and the midline dorsum of the nose (Fig. 22.2). The incision is carried down through skin and orbicularis muscle. The angular vessels are ligated and the periosteum is elevated medially and laterally and retracted with stay sutures that are weighted with small hemostats and laid over gauze sponges covering the eyes. Sequentially, the anterior lacrimal crest, lacrimal fossa and posterior lacrimal crest are identifiers. The medial canthal tendon is released by dissecting the periosteum from the medial orbital wall and retracting the orbital contents laterally with a Sewell retractor. The lacrimal sac is elevated out of the fossa and reflected medially. The lacrimal duct is preserved. If the lacrimal duct is to be sacrificed as for maxillectomy, it is cannulated at the end of the procedure with a double-ended silastic lacrimal stent, one end inserted through each lacrimal punctum.

With use of a Sewell retractor to retract the orbital contents laterally, the dissection extends from superficial to deep along the medial orbital wall and the lamina papyracea. The anterior and posterior ethmoidal arteries are identified and ligated. These serve as a landmark to the level of the floor of the anterior cranial fossa. The pressure head to these arteries is from the ophthalmic artery on the orbital side of the wound. They must not be allowed to retract back into the orbit unligated. A hemaclip is applied to the orbital side, a bipolar cautery used to cauterize the nasal side, and then the vessel is transected medial to the hemaclip. Care is taken to avoid opening the periorbita, which leads to the herniation of orbital fat. The ethmoid sinus is then entered via the lacrimal fossa and this opening is enlarged toward the nasal dorsum with a Kerrison rongeur. The anterior ethmoid cells (agger nasi) are entered with a mas-toid curette and the mucosa forming the lateral nasal wall anterior to the middle turbinate is exposed. An incision is made in this mucosa and the nasal pledgets previously placed in the nose are identified and removed. The middle turbinate and nasal septum can now be visualized. Using the lamina pap-yracea, middle turbinate and ethmoid foraminae as landmarks, one removes the ethmoid cells from anterior to posterior with Blakesley or Takahashi forceps. Approximately the anterior half of the lamina papyracea is resected to allow visualization. Remember that the plane of the fovea ethmoidalis falls inferiorly as one proceeds from anterior to posterior. The orbital contents, cribriform plate and nasal septum are avoided by direct visualization. If necessary, the sphenoid sinus is entered medially and inferiorly and its front wall removed with Kerrison-type forceps. The middle turbinate is resected at its attachment to the skull base with turbinate scissors and removed. The maxillary sinus can easily be entered and any Haller cells removed. The frontal sinus drainage system is immediately accessible. Ono-di cells can be directly visualized along the posterior orbital wall. If an orbital abscess is suspected, the periorbita can be incised and the medial orbital contents explored (Fig. 22.3).

At the conclusion of the procedure, the medial orbital periosteum with its attached medial canthal tendon is reattached to the nasal periosteum.

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