Spectrum of Orbital Cellulitis on Magnetic Resonance Imaging

Abstract

Introduction Orbital infection is an ophthalmological emergency as it can lead to blindness and intracranial spread. Imaging is needed to determine the extent of the infection, to localize an abscess, and for surgical planning. The role of magnetic resonance imaging (MRI) is well established in the evaluation of orbital pathologies, including orbital cellulitis and abscess, mainly due to its ability to evaluate early intracranial involvement. The objective of the study was to highlight the spectrum of MR imaging findings and the pattern of spread in fifteen patients with orbital cellulitis. Methods A prospective study was conducted in a tertiary care hospital. Fifteen patients of all age groups, of either sex, presenting with clinical findings suggestive of orbital cellulitis, referred for MRI of orbits, were included in the study. Written informed consent was obtained prior to the study. Patients' demographic data such as age and gender, associated co-morbidities, complications, and the pattern of spread of disease on MRI were recorded and evaluated. Descriptive statistics were used. Results Orbital/periorbital abscess was found to be the most common complication of orbital cellulitis (eight cases, 53.3%), followed by optic neuritis/perineuritis (four cases, 26.67%), intracranial involvement (four cases, 26.67%), dacryoadenitis (three cases, 20%) and cavernous sinus thrombophlebitis (three cases, 20%). Seven cases (46.67%) had right orbital involvement. Sinusitis was found to be the most common predisposing factor. Amongst the cases associated with sinusitis, the commonest inflamed paranasal sinus was found to be the ethmoid sinus (twelve cases). Amongst the fifteen cases of orbital/periorbital cellulitis, there were only two cases of isolated preseptal cellulitis (13.33%), five cases of postseptal cellulitis (33.33%) and eight cases of both preseptal and postseptal orbital cellulitis (53.33%). Conclusion MRI is the imaging modality of choice in the evaluation of orbital cellulitis because of its superior soft tissue and contrast resolution. It is vital to evaluate the extent of the orbital infection, underlying paranasal sinus involvement, as well as detect complications of orbital cellulitis, especially intracranial spread.

Keywords: abscess; cavernous sinus thrombophlebitis; cellulitis; intracranial complications; magnetic resonance imaging; orbital; thrombosis.

Figure 1. Graph showing the age distribution of fifteen cases of orbital cellulitis

Figure 2. Orbital cellulitis: axial T2WI shows abnormal soft tissue in the left posterior ethmoid air cells (arrow) appearing hyperintense

TW2I - T2-weighted image

Figure 3. Orbital cellulitis: coronal STIR image shows hyperintense soft tissue (arrow) extending into the extraconal compartment of the left orbit, abutting the medial rectus with surrounding fat stranding

STIR - short tau inversion recovery

Figure 4. Orbital cellulitis: axial post-contrast T1WI shows enhancement of the abnormal soft tissue (arrow)

T1WI - T1-weighted image

Figure 5. Orbital abscess: coronal STIR image shows two well defined hyperintense lesions (arrows) in the intraconal and extraconal compartments of left orbit in the inferior and medial aspects

STIR - short tau inversion recovery

Figure 6. Orbital abscess: coronal post gadolinium T1WI shows peripheral enhancement of the lesions (arrows), indicative of abscess

T1WI - T1-weighted image

Figure 7. Preseptal cellulitis with abscess: axial STIR image shows abnormal hyperintense signal in the preseptal region in subcutaneous plane

STIR - short tau inversion recovery

Figure 8. Preseptal cellulitis with abscess: axial post gadolinium T1WI shows diffuse enhancement in the preseptal space with a small peripherally enhancing area medially (arrow), indicative of preseptal abscess

T1WI - T1-weighted image

Figure 9. Periorbital cellulitis: axial STIR image shows preseptal soft tissue thickening on right with hyperintense signal (arrow) involving the preseptal region and extending in the infratemporal fossa

STIR - short tau inversion recovery

Figure 10. Periorbital cellulitis: axial post gadolinium T1WI shows abnormal enhancement of the preseptal soft tissue thickening (arrow) and extending in the infratemporal fossa

T1WI - T1-weighted image

Figure 11. Dacryoadenitis: coronal T2WI shows bulky right lacrimal gland with slight heterogeneous signal (arrow)

T2WI - T2-weighted image

Figure 12. Dacryoadenitis: coronal post gadolinium T1WI shows abnormal enhancement of the enlarged lacrimal gland (arrow)

T1WI - T1-weighted image

Figure 13. Optic perineuritis: coronal post gadolinium T1WI shows mild perineural enhancement around the left optic nerve (arrow), indicative of optic perineuritis. Enhancement is also noted in the extraconal compartment medially, suggestive of orbital cellulitis

T1WI - T1-weighted image

Figure 14. Cavernous sinus thrombophlebitis: coronal post-contrast T1WI (arrow) shows differential enhancement of the right cavernous sinus, suggestive of cavernous sinus thrombophlebitis

T1WI - T1-weighted image