Julien W. Hsieh

Acute invasive fungal rhinosinusitis (AIFR) is a rare, severe, and life-threatening opportunistic infection associated with high mortality and morbidity. Rapid and accurate diagnosis and treatment are crucial for survival and effective disease management. Diagnosing AIFR is challenging because no single pathognomonic feature exists other than surgical biopsy showing fungal angioinvasion and necrosis. This narrative review focuses on the diagnostic challenges and pitfalls, emphasizing the critical clinical value of magnetic resonance imaging (MRI) for early diagnosis of AIFR. It includes selected cases that illustrate the significance of MRI. When AIFR is suspected, clinical symptoms, nasal endoscopy, blood samples, and facial computed tomography all provide non-specific information. In contrast, MRI can identify signs of devitalized sinonasal mucosa consistent with AIFR. The absence of mucosal enhancement on T1-weighted images, combined with restricted diffusivity, are characteristic MRI features of AIFR. The cases presented underscore the usefulness of MRI in supporting clinical suspicion of AIFR and accurately determining its topography, thereby guiding early surgical biopsies and debridement. In suspected cases of AIFR, MRI serves as a valuable supplementary, non-invasive tool to help determine whether prompt surgical biopsy or debridement is necessary, thereby enhancing early diagnosis and improving survival rates. Therefore, the threshold for conducting an MRI in these cases should be low.