Utility of Fluorescent Microscopy for Rapid Intraoperative Diagnosis of Rhinocerebral Mucormycosis: Experience from a Tertiary Care Center in Central India.

Rhino-orbital-cerebral mucormycosis is an uncommon life-threatening infection caused by the angioinvasive fungus Mucorales and is associated with high morbidity and mortality. In India, the pandemic of COVID-19 was associated with another deadly disease, rhinocerebral mucormycosis, which further complicated the course of the disease, necessitating an accurate and rapid diagnosis. Conventional methods of diagnosis, like fungal culture, histopathology, Gomori methenamine silver (GMS), and periodic acid-Schiff (PAS) stain, are not feasible for intraoperative diagnosis. We studied the use of fluorescent brightener calcofluor white (CFW) for rapid intraoperative diagnosis of mucormycosis and compared it with intraoperative crush smear cytology and frozen section. A total of 37 intraoperative samples were studied, of which 11 were positive for the fungus. Calcofluor white detected fungus in seven samples, while frozen section detected fungus in eight samples. Calcofluor white stain showed less sensitivity than the frozen section but had high specificity. In the presence of marked necrosis, suspicious fragments on frozen sections could be quickly confirmed by fluorescent stain. Thus, CFW direct microscopy is a useful adjunct for the rapid diagnosis of mucormycosis.