How is surgery performed for allergic fungal sinusitis (AFS)?

Updated: Mar 16, 2018
  • Author: John E McClay, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

At surgery, 3 surgical goals should be achieved: (1) complete extirpation of all allergic mucin and fungal debris, (2) permanent drainage and ventilation of the affected sinuses while preserving the integrity of the underlying mucosa, and (3) postoperative access to the previously diseased areas.

First, surgery should result in complete extirpation of all allergic mucin and fungal debris, thus greatly reducing or eliminating the antigenic inciting factor within the atopic individual, as depicted in the image below. At times, this may be challenging because the nasal polyposis inherent in allergic fungal sinusitis (AFS) can range from subtle to extensive, causing distortion of local anatomy and loss of useful surgical landmarks. Bleeding often occurs in response to surgical manipulation of the polyps, increasing the potential for disorientation. The operating surgeon must recognize that these factors, in combination with the high likelihood of bony dehiscence, increase the risk of iatrogenic injury.

Immediate postoperative 30° angled view showing th Immediate postoperative 30° angled view showing the complete removal of polyps with a widened frontal sinus recess superiorly and widened ethmoid cavity in the mid portion. The middle turbinate is on the right, pushed against the septum. The lateral nasal wall is on the left.

Aside from these problems, polyps can provide an important intraoperative role by serving as a marker of disease. Allergic fungal sinusitis (AFS) causes a relatively consistent configuration of disease. The involved paranasal sinus, acting as a reservoir for allergic fungal mucin, is the epicenter of the disease process. Allergic fungal mucin completely occupies the sinus cavity and almost always is mixed with fungal elements, as depicted in the images below, while the lining mucosa, demonstrating only mild-to-moderate inflammation, remains an intact barrier to the fungus. More significant inflammation located at the sinus ostia gives rise to polyps that extend into the infundibulum, middle meatus, sphenoethmoid recess, and nasal cavity. Recognition of this allows the surgeon to follow the polyps to the disease.

Fungal ball in the right maxillary sinus. Fungal ball in the right maxillary sinus.
Fungal debris being removed from the ethmoid compl Fungal debris being removed from the ethmoid complex. A suction device is seen in the right lower corner of the picture.
Allergic mucin, fungal debris, and polyps are show Allergic mucin, fungal debris, and polyps are shown after removal from the patient. The scale is in inches.

The allergic mucin, not the polyps, should be sent to a pathologist to confirm the diagnosis of allergic fungal sinusitis (AFS; see Histologic Findings). The fungal elements and mucin can be sent for culture and pathologic stain to help make the diagnosis and identify the fungus responsible for the disease. Fungal stains are positive more often than fungal cultures, but both should be attempted.

Resulting nasal polyposis also can facilitate surgical treatment of allergic fungal sinusitis (AFS) in another fashion. The expansile behavior of allergic fungal sinusitis (AFS) increases access to involved paranasal sinuses. As revealed radiographically, the combination of slowly growing nasal polyps and accumulating allergic fungal mucin expands the involved paranasal sinuses and the surgical route to the involved sinuses. Enlargement of the nasal cavity, middle meatus, and frontal recess provides the surgeon with access adequate to address the disease, even in the most difficult areas, such as the lateral area of the frontal sinus, which once was thought to require a traditional nonendoscopic approach, as depicted in the image below.

Coronal CT scan showing extensive allergic fungal Coronal CT scan showing extensive allergic fungal sinusitis involving the right side with mucocele above the right orbit and expansion of the sinuses on the right.
Coronal CT scan showing the postoperative view fol Coronal CT scan showing the postoperative view following removal of disease after significant disease recurred on both the right and left sides of the nasal cavity and sinuses; mild mucosal thickening of all involved sinuses is present, with some moderate thickening of the left maxillary sinus. All disease, even the lateral mucocele, was removed or drained endoscopically.

After surgical access to the involved sinus is achieved, a dilated cavity filled with allergic fungal mucin is encountered. This material is thick, tenacious, and viscous and may vary in color from light tan to black. Because of its noninvasive behavior, it may be removed in a blunt fashion, leaving the involved sinus completely lined with intact mucosa. Preservation of mucosa provides protection of adjacent anatomic structures, even in the face of large areas of bony dehiscence.

The next goal of surgery is to produce permanent drainage and ventilation of the affected sinuses while preserving the integrity of the underlying mucosa. This has been aided greatly by the recent advent of tissue-sparing instrumentation. Even in the setting of significant dissolution of the fovea ethmoidalis, lamina papyracea, clivus, and sphenoid planum, wide marsupialization of diseased areas can be achieved without causing trauma to the underlying mucosa. Careful preservation of mucosa ensures that underlying periosteum, dura, and/or periorbita remain free of penetrating injury. Sinonasal polyposis initially may preclude orientation, but removal in a controlled fashion using powered microdissection provides the operating surgeon with eventual access to areas of fungal presence. After adequate ventilation and drainage are achieved, the preserved underlying mucosa is able to revert to its normal state.

Adequate ventilation and drainage also provide for the final goal of surgery, postoperative access to the previously diseased areas. Even under ideal conditions, small residua of fungus may remain in situ, inciting recurrence if not controlled postoperatively. Surgery should be performed with facilitation of postsurgical care in mind. This goal can be attained reliably in most patients while preserving the integrity of important intranasal structures, such as the middle and inferior turbinates.

These surgical goals can be accomplished through a number of approaches and techniques, the choice of which ultimately is influenced by the experience and training of the surgeon. Endoscopic powered instrumentation has demonstrated its effectiveness; this technique allows for removal of soft tissue and thin bone while maintaining superb visibility. Exercise great care when using powered instrumentation because the well-recognized bone dissolution associated with allergic fungal sinusitis (AFS) increases the potential risk of inadvertent orbital and/or intracranial penetration. In the event of extensive remodeling or bone erosion, image-guided systems (eg, Stealth, InstaTrak) may be of benefit.


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