Beware the Trojan Horse

The patient had further contrasted MRI imaging of the head and orbit, showing persistent soft tissue swelling of the left orbital apex with intracranial extension along the meninges in the left temporal fossa and left cavernous sinus, and focal skull base osteomyelitis. She underwent a second trans-sphenoidal endoscopic biopsy and debridement of the left orbit. Gram stain of the biopsy showed pus cells but no organisms, and calcofluor stain did not demonstrate fungi. Nevertheless, enrichment cultures grew Pseudomonas aeruginosa sensitive to tazobactam. Importantly, histology of the second biopsy showed an acute on chronic sino-sinusitis with pyogenic response consistent with a bacterial not fungal infection. The patient was maintained on oral ciprofloxacin monotherapy and began to demonstrate clinical improvement with normalization of her renal function. Retrospectively, we found she had a 6-month history of chronic left otalgia following an episode of otitis externa that was treated with a short course of oral ciprofloxacin. Ear swabs at that time grew skin flora and pseudomonas species that were thought to represent colonization by these organisms only. Though she did not complain of otorrhea or otalgia at the onset of her orbital signs, the ear canal was the most likely source of infection. Diabetics are particularly susceptible to malignant otitis externa (MOE) complicated by skull base osteomyelitis and multiple cranial neuropathies, which has a mortality of up to 50%1 . Prompt diagnosis by tissue biopsy combined with debridement of necrotic tissue is required to maximize outcome4 . Although most cases are caused by Pseudomonas aeruginosa, fungi and other organisms are also implicated 2,3 . The facial nerve or lower cranial nerves are most commonly involved in MOE, whereas involvement of the optic nerve is rare5-7 . Nevertheless, an otological history ought to be sought from diabetic patients with suspected orbital infection.