Neurosurgical Management of Bipolaris-Specific Skull Base Allergic Fungal Sinusitis: Diagnostic Criteria and Outcome

Neurosurgical Management of Bipolaris-Specific Skull Base Allergic Fungal Sinusitis: Diagnostic Criteria and Outcome O the past decade, the incidence of fungal infections has increased dramatically. Fungal paranasal sinus disease, a large component of fungal infections, is common and is defined by the host and the host’s response to the fungus. Invasive fungal sinusitis occurs in immunocompromised hosts and can manifest as acute, fulminant, and lifethreatening or as a more manageable chronic/granulomatous indolent form. However, the hallmark of invasive disease is the presence of large amounts of the fungal element in the associated pathology without immune containment. In contrast, noninvasive fungal sinusitis occurs in immunocompetent individuals. It exists in two forms, both characterized by the host’s response to the fungal agent. With the first, mycetoma, the host’s immune response is inadequate and the fungal agent proliferates as an encapsulated mass. The second, AFS, the subject of this report, occurs when the host provides an overly exuberant immune response to the antigens of the fungus. Skull base allergic fungal sinusitis, a term first introduced by Kinsella et al., denotes the specific condition in which AFS extends intracranially.10 Ten to 20% of patients with AFS have an intracranial extension.13 Once SBAFS is encountered, neurosurgical intervention is required. Because of their variable presentation and rarity, these lesions are seldom expected preoperatively.15 Consequently, SBAFS is often mistaken for a malignancy,11,12,18,27 and patients may receive overly aggressive therapy. Because SBAFS is noninvasive, surgical debulkment is standard therapy; radical resection or toxic medSkull base allergic fungal sinusitis is a rare but important neurosurgical entity that can be mistaken for a skull base tumor during preoperative assessment. Due to the significantly variable clinical presentation of and preoperative evaluation for this disease, clinicians are often surprised when the diagnosis becomes apparent during surgery or thereafter. However, SBAFS must be differentiated from malignancy and invasive fungal disease because this allergic disease does not require aggressive, complete resection or potentially toxic antifungal medications. We report six cases of SBAFS to illustrate the neurosurgical management of this rare disease.