Orbital compartment syndrome in orbital mucormycosis: spot the threat through radiologist's eye.

Purpose: To illustrate the imaging findings of orbital compartment syndrome (OCS) in patients with orbital mucormycosis and to identify the red flag signs on imaging for prompt diagnosis and timely intervention.

Methods: We conducted a retrospective analysis of CT and MRI scans from patients diagnosed with sino-nasal mucormycosis within three months of a confirmed COVID-19 infection. Microbiologically proven cases of mucormycosis were included. Images were analysed for: Route of spread; proptosis; tenting of globe, Retro-orbital fat/extraocular muscle (EOM) nonenhancement; Intra-orbital abscess, superior ophthalmic vein (SOV) thrombosis, stretching/thickening/enhancement/diffusion restriction of optic nerve, orbital coat, and EOM. Descriptive statistics were elaborated in the form of mean/standard deviations for continuous variables and frequencies and percentages for categorical variables.

Results: Out of 138 patients with mucormycosis, 49 had orbital involvement, OCS was present in 16 orbits. The mean age was 48.6 years with M: F of 2.75:1. Adjacent sinuses were involved in all patients. Spread along nerves and nasolacrimal duct was seen in 94% patients. Globe tenting was seen in all and thickening/coat enhancement in 53.3%. Optic nerve (ON) was thickened in 87.5%, diffusion restriction of ON and EOM in 78.5% cases. Non enhancement of retro-orbital fat was seen in 50% and intra-orbital abscess in 62.5% cases.

Conclusions: OCS is a vision-threatening orbital emergency, leading to OIS and permanent blindness, if not managed promptly. Imaging features that warrant immediate clinical/ surgical intervention to avoid permanent loss of vision are distorted globe, posterior tenting of the globe, stretching of the optic nerve, non-enhancement of retro-bulbar fat and extra-ocular muscles (EOMs).