Fungus Ball

Overview:
-Also known as mycetoma
-Relatively uncommon manifestation of fungal sinusitis
-Most widely accepted pathogenesis theorizes a deficient mucociliary
clearance mechanism in which fungal organisms deposited in the
paranasal sinuses are inadequately cleared
-Fungal organisms germinate, replicate, and incite an inflammatory
response within the paranasal sinus
-Represents a tangled collection of fungal hyphae in a mucoid matrix
-Most commonly caused by Alternaria, Aspergillus, and
Pseudallescheria

Clinical Presentation:

-Tends to be a disease of older individuals with an apparent female
predilection
-Afflicted individuals are immunocompetent
-Variable clinical presentation; may sometimes be asymptomatic
-Individuals commonly describe a chronic pressure sensation involving
one of the paranasal sinuses
-Other symptoms include nasal discharge and cacosmia (foul smelling)
-May be associated with proptosis or seizures if complicated by
intraorbital or intracranial extension.

Imaging:

-Fungus ball appears as a mass within the lumen of a paranasal sinus
-Usually limited to one paranasal sinus
-Maxillary sinus involvement is most common, followed by the sphenoid
sinus
-Appearance is typically hyperdense on non-contrast CT
-May demonstrate punctate calcifications within the fungus ball
-Appears hypointense on T1 WI and T2 WI
-Calcifications and paramagnetic metals such as iron, magnesium, and
manganese generate areas of T2 WI signal void
-Inflamed mucosal lining of the paranasal sinus is frequently hypodense
on non-contrast CT and hyperintense on T2 WI (MRI)
-Bony walls of the paranasal sinus may be sclerotic and thickened or
expanded and thinned with focal areas of erosion from pressure
necrosis

Treatment and Prognosis:

-Treatment requires surgical removal and restoration of drainage of the
paranasal sinus
-Antifungal medications are generally unnecessary
-Recurrence is rare