Endoscopic frontal sinusotomy can be performed under local or general anesthesia depending on the patient's preference, the surgeon's experience, the health and age of the patient, and the severity of the sinus problem.
As previously described for ethmoidectomy and antrostomy, surgery begins with a careful examination of the nose. The extent of the frontal sinusotomy is determined by the site of frontal sinusitis and the variations in the patient's anatomy which may predispose them to sinusitis.
In those patients with sinusitis secondary to obstructing disease within the frontal recess area of the ethmoid sinus, surgery is directed towards removal of this disease. This procedure is known as a type I frontal sinusotomy. The procedure usually begins with a partial or total ethmoidectomy as described elsewhere. Following ethmoidectomy the remaining ethmoid cells within the frontal recess, polyps and uncinate process are removed. The procedure is complete when the ostium or opening of the frontal sinus is exposed and this sinus can freely drain into the nose.
Illustration of frontal sinusitis (1, orange) secondary to obstruction of the frontal recess (2, yellow). Such obstruction could be secondary to nasal polyps, scarring from prior surgery or variations in anatomy of the frontal recess (such as the uncinate process or ethmoid cells obstructing frontal sinus drainage).
The next level of surgical complexity in the treating frontal sinusitis is the removal of part, or the entire floor of one or both frontal sinuses. These procedures are known as type IIa and type IIb frontal sinusotomies, respectively.
Type I endoscopic frontal sinusotomy. Intraoperative photograph shows the frontal sinus (FS) is exposed after removal of anterior ethmoid cells. As the diseased mucous membrane and remaining anterior ethmoid cells were removed, the entire frontal sinus became evident (dotted line).
Illustration of type II frontal sinusotomies. Type IIa consists of removing the floor of the frontal sinus between the lamina papyracea (the bony wall separating the orbit from the ethmoid sinus) and the middle turbinate. Type IIb frontal sinusotomy in the removal of the entire floor of the frontal sinus. Unlike a type III frontal sinusotomy, the nasal septum and intra-frontal septum are undisturbed.
Coronal CT scan of patient with bilateral frontal sinusitis (1) secondary to extension of ethmoid cells (2, also described previously as a frontal cell) into the floor of the frontal sinus. These ethmoid cells literally balloon into the floor of the frontal sinus and are visible due to the contrast between the mucous in the frontal and ethmoid sinuses (1) and the air within the ethmoid or frontal cells (3).
Type II frontal sinusotomy is usually performed in conjunction with ethmoidectomy. The extent of removal of the floor of the frontal sinus is determined by the etiology of the obstruction, the site of the sinusitis and history of prior surgery. Individuals with small openings from their frontal sinus to the nose, and scarring within the frontal recess area, are more likely to require removal of the entire floor of the affected frontal sinus, than those who have discrete anatomic anomalies which can be completely removed to permit drainage of the sinus. The latter is shown below and restoration of frontal sinus drainage is limited to removing an ethmoid cell which constitutes the lateral floor of the sinus.
A. Ethmoid cell or frontal cell (green ellipse) extending into the floor of the frontal sinus.
B. Restoring drainage of the frontal due to an obstructing frontal cell has been likened to removing an egg from an inverted egg cup (dotted blue line [Stammberger, 2000]).
Intraoperative photograph demonstrates the Stammberger analogy of removing an egg from an inverted egg cup as visualized from the perspective of being within the cup (Stammberger, 2000). The top of the inside of the egg is the upper surface of the frontal cell (1). The egg cup is the surrounding bony perimeter of the frontal recess and frontal sinus. The forceps (2) are shown beginning the removal of the egg (i.e., the frontal cell) without injuring the egg cup.
As the ethmoid cell (EC) is removed the frontal sinus (FS) becomes visible.
Further removal of the ethmoid cell reveals part of the frontal sinus. As surgery further progressed, the remaining ethmoid cell was removed (encompassed by green dotted line) leaving the mucous membrane lining the frontal recess (blue dotted line) intact.
When frontal sinusitis is due to either bone or dense scar from prior surgery obliterating the communication of the frontal sinus to the nose, one approach to restoring drainage is to remove the entire floor of both frontal sinuses. This procedure is known as a type III frontal sinusotomy (Weber, 2002).
The elements of type III frontal sinusotomy are removal of the entire floor of both frontal sinuses, the intrasinus septum which divides the frontal sinus into a left and right cavity and upper nasal septum.
Intraoperative CT reconstruction utilizing computer assisted image guided surgery. In this image, the end of a probe placed within the right frontal is identified as the convergence of the vertical and horizontal lines. To restore drainage of the frontal sinus, the floor of the sinus (1) is removed as are the intrasinus septum (2) and the upper nasal septum (3).
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