A 36-year-old female presented with gradually increasing left eye swelling, progressive loss of vision and left-sided facial pain for 2 months. A few days prior to the peaking of symptoms, she had symptoms of cold. She was a known diabetic and hypertensive. On examination (Figure 1a,b), there was left periorbital oedema, swelling on the dorsal aspect of the root of the nose and lower conjunctival oedema with mild proptosis of the mucosa. The patient was unable to open the left eyelid completely. She could not perform any ocular movements. The pupil was fixed and dilated. On ophthalmoscopy, the disc appeared pale. Blood sugar level at the time of admission was 280 mg dl-1. The surgeon suspected left paranasal sinus pathology with orbital extension and requested a CT scan of the paranasal sinuses and an MRI of the orbits with screening of the brain.
CT scan of the paranasal sinuses (Figure 2a-c) demonstrated mild mucosal thickening of the left maxillary and ethmoid sinuses, bony defect in the alveolar margin of the maxilla at the root of the left incisor tooth and an oroantral fistula. CT scan of the orbital region demonstrated proptosis of the left globe, retro-orbital fat stranding and soft tissue thickening along the medial wall of the orbit with subtle bony erosion in the left lamina papyracea.
 T 1 weighted images (Figure 3a) demonstrated fat stranding in the retro-orbital, orbital apex and left cavernous sinus regions, with minimal proptosis of the left globe.
 T 2 weighted fat-saturated axial images (Figure 3a,b) and short tau inversion-recovery coronal images (Figure 3d) demonstrated extensive fat stranding in the retro-orbital region; ill-defined isointense to hypointense soft tissue along the medial wall of the left orbit and the intraconal retro-orbital space, which extended to the orbital apex. The extraocular muscles appeared oedematous. Left internal carotid artery flow void was small in calibre with adjacent soft tissue thickening in the left cavernous sinus. A small focal hyperintense collection was seen in the left preseptal space.
Diffusion-weighted images (Figure 4a-e) showed restricted diffusion in the two intraorbital lesions (including the encased optic nerve) with low apparent diffusion coefficient values (0.45 x 10-3 mm2 s-1). The preseptal lesion did not show any restriction of diffusion. Multiple small acute infarcts were seen in the left corona radiata and parietal lobe with an apparent diffusion coefficient value similar to the orbital lesions (0.407 x 10-3 mm2 s-1).
Susceptibility weighted imaging (Figure 5a) demonstrated blooming in the two intraorbital images. MR angiography (Figure 5b) demonstrated narrowing of the left internal carotid artery from its origin, involving both the intracranial and extracranial portions.
Post-contrast fat-saturated T 1 weighted images (Figure 6a-d) demonstrated three peripherally enhancing lesions in the left orbit. A 15 x 8 x 10 mm lesion was seen in the extraconal space on the medial aspect of the orbit subperiosteally, displacing the medial rectus laterally with subtle enhancement in the left ethmoid sinus (Figure 6a). A 33 x 18 x 15 mm intraconal retro-orbital lesion was seen communicating with the lesion along the medial wall and extending to the orbital apex and the left cavernous sinus, with the intracranial component measuring 7 mm (Figure 6a,c). The left optic nerve was encased by the intraconal lesion with enhancement in the distal part of the optic nerve close to its insertion into the globe (Figure 6a,b). The enhancement was seen to extend along the left internal carotid artery, which had a small calibre with a thickened wall (Figure 6a-d). There was also inferior extension into the left pterygopalatine fossa (Figure 6b). The third lesion was seen in the lower preseptal space measuring 23 x 7 x 9 mm and showed signal intensity similar to fluid with peripheral enhancement.
Surgical endoscopic excision of the orbital lesion was performed. Intraoperatively, cheesy white material with whitish spots was noted. It was thick in consistency and showed minimal bleeding on dissection.
Tissue samples from the left orbit and orbital apex on haematoxylin and eosin staining showed necrotic tissue with inflammatory cells composed of neutrophils, lymphocytes, plasma cells, histiocytes and a few giant cells amid which were seen broad, aseptate, obtuse-angle branching hyphal elements (Figure 7a,b). The presence of fungal elements was confirmed with periodic acid-Schiff staining (Figure 7c).
Tissue samples from the left ethmoid and maxillary sinuses demonstrated moderate chronic inflammatory cell infiltrate and fragments of bony lamellae. Tissue samples from the left ethmoid sinus demonstrated epithelioid granuloma with giant cells. However, acid-fast bacillus stain and culture were negative and so tuberculosis was ruled out.