CLINICAL HISTORY: 68 years of age, Male, history of cirrhosis, concern for invasive fungal infection of the sinuses.
Sinuses, anterior skull base, and extra-axial spaces: Again seen is near complete opacification of the left frontal sinus, with thick T2 hyperintense mucosal thickening peripherally and central T2 hypointense, T1 hyperintense nodule which measures 20 x 8 mm suggestive of a mycetoma/chronic fungal colonization. There are 2 suspected dehiscences of the posterior wall of the frontal sinus which are better demonstrated on prior CT, with larger dehiscence inferiorly extending into the anterior aspect of the fovea ethmoidalis/anterior skull base. Smaller dehiscence seen more superiorly. In the underlying epidural space, there is material which previously demonstrated enhancement and is predominantly T2 hypointense with patchy areas of T2 hyperintensity, predominantly representing epidural phlegmon. The areas of more T2 hyperintensity correspond to small pockets of restricted diffusion and likely represent tiny abscess pockets. Compared with prior MRI, phlegmon appears unchanged in extent over the left anterior frontal convexity and mildly decreased in thickness, now measuring up to 3 mm in maximal thickness, previously 6 mm at same level on prior exam. No mass effect on the underlying brain parenchyma.
Additionally, there are small paired subdural collections on both sides of the anterior falx extending superiorly from the anterior aspect of the anterior skull base, which demonstrate restricted diffusion compatible with subdural empyemas. Subdural empyemas are unchanged extent from prior exam and appears slightly decreased in thickness though difficult to optimally measure given small size. Inferior aspect of collection extends to the level of suspected inferior dehiscence and abuts epidural phlegmon.
Parenchyma: No acute infarct, focal lesion or restricted diffusion, edema, or mass effect to suggest parenchymal abscess. Moderate global volume loss.
Ventricles: Ex vacuo prominence related to global volume loss.
Orbits: Status post bilateral lens replacement.
Mastoid air cells: Clear.
Bones: Anterior skull base findings as above. Degenerative changes of the temporomandibular joints.
Additional comment: None.
1. Findings compatible with left frontal sinus mucosal disease and possible mycetoma, with two possible dehiscences of posterior wall of the left frontal sinus/anterior skull base and intracranial extension of infection with small epidural phlegmon and parafalcine subdural empyemas. While examination is somewhat limited in the absence of intravenous contrast which could not be administered due to impaired renal function, noncontrast exam shows decreased thickness of both epidural phlegmon and to lesser degree subdural empyemas, which are unchanged in extent. Both are small and exert no mass effect on the underlying brain parenchyma. No evidence of parenchymal brain abscess.
2. Imaging findings have concerning elements for fungal infection; T2 hypointense lesion within the left frontal sinus is suggestive of mycetoma, and lower T2 intensity material within the epidural phlegmon could represent fungal elements. However, central restricted diffusion with high T2 signal of subdural empyema is more typical bacterial etiology, and given suspected on dehiscence, polymicrobial infection is possible. Fundamentally, this exam cannot distinguish typical bacterial from fungal infection, though both should be considered.
3. Bony defects are poorly evaluated on MRI, and prior outside imaging is relatively thick section. If better delineation of bony dehiscence is required, consider thin section CT of the anterior skull base.
(Frontal sinusitis with epidural abscess and subdural empyema)