Skull-base osteomyelitis: fungal vs. bacterial infection.

Skull-base osteomyelitis (SBO) occurs secondary to invasive bacterial and fungal infection. Distinguishing between fungal and bacterial aetiologies of SBO has significant therapeutic implications. An 18-year (1990-2007) retrospective review of patients with SBO presenting to Westmead Hospital was performed. Epidemiological, clinical, laboratory and radiology data were collated. Twenty-one patients (median age 58 years) with SBO were identified: ten (48%) had bacterial and 11 (52%) had fungal SBO. Diabetes mellitus (57%) and chronic otitis externa (33%) were the most frequent co-morbidities; immunosuppression was present in five cases (24%). Cranial nerve deficits occurred in ten (48%) patients. The commonest pathogens were Pseudomonas aeruginosa (50% bacterial SBO) and a zygomycete (55% fungal SBO). Compared to bacterial SBO, fungal SBO was more frequently associated with underlying chronic sinusitis, sinonasal pain, facial/periorbital swelling and nasal stuffiness or discharge and the absence of purulent ear discharge (all p <0.05). Bacterial SBO was more frequently associated with deafness, ear pain or ear discharge (all p <0.05). Median time to presentation was longer in patients with bacterial SBO (26.3 weeks vs. 8.1 weeks, p 0.08). Overall 6-month survival was 88% (14/18 patients). All four deaths occurred in patients with fungal SBO. Immunosuppression was a risk factor for death (p <0.05). Early diagnostic sampling is recommended in patients at increased risk of fungal SBO to enable optimal antimicrobial and surgical management.