Discussion
Globally, the prevalence of unilateral involvement of paranasal sinuses is higher than bilaterally. However, with the present study, this index, related to the frontal sinus fungal ball, is equivalent, corresponding to 50% of unilateral involvement and 50% of bilateral involvement, perhaps due to some anatomical alteration of the frontal sinus.
All reported cases of fungal ball in the frontal sinus affected male patients, contrary to the common female prevalence in fungal ball of the other paranasal sinuses; a possibility for this gender difference may be hormonal. The average age of the reported cases is 65.29 years, with a minimum age of 61.16 and a maximum age of 69 years, exceeding the age range common to other fungal balls with paranasal sinuses; the fact that it occurs in older patients may be related to the delay in the proliferation of fungi, reaching more this age group21.
The aerogenic hypothesis22 suggests that fungal spores are deposited on the mucosa by inhalation and acquire pathogenic capacity when in anaerobic conditions within the sinus23. Other authors indicate osteomeatal complex obstruction or chronic rhinosinusitis as predisposing24. However, this theory does not explain the cases of fungal ball that affect the sphenoid or frontal sinus. Not all patients with occluded frontal sinuses develop a fungal ball, which probably means that spores are not always able to reach the frontal sinus due to the complex anatomy of the frontal recess.
Of the several anatomical sinonasal variants, the presence of bullous shell was significantly associated with the development of fungal ball, as well as a narrow infundibulum and anatomical variations in the region of the ostiomeatal complex, known to cause sinus hypoventilation, may also be related to this pathogenesis25. Concomitant to this, our patient also had fronto-ethmoidal cells that obstructed the frontal recess, which may explain the pathophysiological mechanism.
The therapeutic approach of choice is the endonasal endoscopy in any paranasal sinuses, as the pharmacological treatment does not result in improvement of the condition. The endonasal endoscopic therapeutic approach corresponded to 80% of cases with frontal osteoplasty reserved only for those in whom the endonasal approach is not possible.
Many important neurovascular structures are adjacent to the frontal sinus, putting the patient at risk for orbital and intracranial complications. Thus, the presence of a fungal ball in the frontal sinus, although non-invasive, is potentially much more serious when compared to the involvement of the other sinuses. Thus, early diagnosis and surgical intervention are essential.