Neurosurgical implications of allergic fungal sinusitis

OBJECT: Allergic fungal sinusitis (AFS) is a form of paranasal mycosis that often involves bone destruction and extension into the orbit and anterior skull base. Treatment consists of surgical extirpation and a course of corticosteroids. Despite frequent intracranial involvement, AFS is rarely reported in the neurosurgical literature. METHODS: The records of 21 patients with the histological diagnosis of AFS were reviewed. The histological diagnosis was based on findings of branching septated fungi interspersed with eosinophilic mucin and Charcot-Leyden crystals without fungal invasion of soft tissue. The average age of the 21 patients in this study was 25 years (range 9-46) and the male/female ratio was 3.75:1. All patients were immunocompetent. All had a history of chronic sinusitis and imaging findings of expansile disease involving multiple sinuses. Fifteen patients had nasal polyposis, eight had erosion of bone, which was observed on computerized tomography (CT) scans, eight had disease extending intracranially, and six had disease that involved the lamina papyracea. All patients underwent transnasal and/or transmaxillary endoscopic approaches for debridement and irrigation, six underwent orbital decompression, and three underwent a bifrontal craniotomy for removal of intracranial extradural disease. No patient had a cerebrospinal fluid leak. Postoperatively, one patient was treated with amphotericin B and the other 20 were treated with a short course of corticosteroids. The follow-up period ranged from 2 to 19 years. CONCLUSIONS: Allergic fungal sinusitis is a unique form of fungal disease that may mimic anterior skull base and paranasal sinus tumors. A cranial base team approach of neurosurgeons and otolaryngologists is recommended. Most cases can be successfully managed with transnasal and/or transmaxillary endoscopic techniques. A craniotomy is rarely indicated unless there is the suspicion of dural invasion or extensive intracranial and/or intraorbital involvement that is inaccessible from below.