Optic nerve restricted diffusion in rhinocerebral mucormicosys

A 54-year-old male patient with chronic liver failure and alcoholism was admitted in our hospital with an acute right orbital apex syndrome and vision loss with 3 days of evolution, no fever. Brain CT revealed inflammatory changes in the right paranasal sinuses with blurring of the orbital apex fat.

There were inflammatory changes in the right paranasal sinuses and orbit, with blurring of the orbital fat and enhancement of the retromaxilary fossa structures (Fig. 1, 2). DWI established the presence of optic nerve infarction, demonstrated by restriction in water mobility (Fig. 3, 4).

Rhino-orbito-cerebral mucormycosis is an acute and fulminant infection.
Patients present with nonspecific complaints such as headache, low-grade fever, facial swelling, sinusitis, and ocular symptoms. Due to its lethal nature, mucormycosis must be recognised early and treated aggressively without waiting for onset of tissue necrosis. Orbital involvement results from spread through the nasolacrimal duct, thin medial orbital wall and commonly presents with proptosis, intra-orbital muscular thickening and obliteration of fat shadow.
In the literature we found only a few cases reporting this peculiar finding in DWI sequences, showing a characteristic pattern of acute optic nerve infaction in patients with mucormycosis [1, 2, 3, 4, 5], possibly due to infiltration of the optic nerve by Mucor organisms. The main contribution of MR imaging to the diagnosis of mucormycosis is its clear demonstration of the relationship between nasal, sinus, and orbital disease along with tissue necrosis, a relationship so typical of mucormycosis that this diagnosis should be considered whenever combined nasal, sinus, and orbital diseases are encountered, especially in an immunodepressed patient [2]. Another author also described similar findings in DWI sequences in a patient with a staphylococcus aureus infection of the optic nerve [6].
The addition of DWI increases the imaging diagnosis of ischaemic optic neuropathy, as shown in this patient, and we should add this sequence in our protocol if optic nerve infarction is suspected. Restricted diffusion on MR imaging may be the earliest abnormality detectable in acute ischaemic optic neuropathy due to rhinocerebral mucormycosis.
In our case the ophthalmologic examination confirmed the diagnosis of central retinal artery oclusion, and tissue biopsy confirmed the diagnosis of mucormycosis (Fig. 5). Despite aggressive treatment the patient died shortly after admission.