OBJECTIVE: We sought to document the diagnostic and management difficulties in masked skull base osteomyelitis secondary to malignant otitis externa, with emphasis on establishing diagnostic criteria in recurrence. STUDY DESIGN: Retrospective analysis of 3 cases of inadequately treated malignant otitis externa in elderly diabetic individuals leading to recurrence and atypical manifestations of skull base osteomyelitis on contralateral side with or without multiple cranial nerve involvement. RESULTS: Two of the 3 cases died of the disease despite aggressive treatment. One case was treated successfully with combination of antipsuedamonal microbial drugs for 8 to 12 weeks and hyperbaric oxygen therapy. Major complications such as thrombosis of lateral sinus and internal jugular vein, meningitis, ophthalmoplegia, blindness, cervical spine erosion and paralysis of all cranial nerves with exception of 1st cranial nerve were observed. CONCLUSION: There is high morbitity and mortality associated with skull base osteomyelitis. In partially treated cases of malignant otitis externa, atypical symptoms and findings of unilateral severe otalgia, unremitting headache, and presence of high ESR, unilateral OME, constitute diagnostic clues of skull base osteomyelitis. Such cases require further investigation with CT, MRI, Technetium 99 and gallium 67 scintigraphy and aggressive management. (c) 2005 American Academy of Otolaryngology-Head and Neck Surgery Foundation, Inc. All rights reserved.