Proteus Mirabilis Skull Base Osteomyelitis with Canal Cholesteatoma in an Immunocompetent Teenager: Surgical and Medical Management

Objective: Description of a rare case of skull base osteomyelitis from Proteus mirabilis in an immunocompetent teenager, including a discussion of her diagnosis and management with literature review.

Methods: Case report from a tertiary-care urban pediatric hospital.

Clinical Case: An otherwise healthy 15-year-old girl presented with a left preauricular abscess and otorrhea. The external auditory canal (EAC) was filled with granulation tissue. Other than moderate ear pain and hearing loss, she did not have any other symptoms or neuropathies. Her initial presentation was typical for a first branchial anomaly, and the abscess was aspirated and sent for culture. An MRI showed severe inflammatory changes along the temporal bone and skull base extending to the clivus, consistent with skull base osteomyelitis. CT showed bony erosive changes in the EAC and osteomyelitis involving the temporal bone and clivus without cranial nerve foramina changes.

Abscess cultures were consistent with Proteus mirabilis. She was started on moxifloxacin and underwent mastoidectomy with canalplasty and debridement. A large canal cholesteatoma was found, with associated bony erosive changes but without extension to the glenoid fossa. Bony biopsy confirmed osteomyelitis without fibrous dysplasia.

Moxifloxacin was continued for 6 months. By 8 months postoperatively, she had neo-ossification of her EAC with complete bony stenosis. A CT showed bony regrowth in the EAC and mastoid, with soft tissue in the middle ear space. Using intraoperative image guidance, a revision mastoidectomy was performed including drillout of the EAC and removal of new bone over the facial nerve canal. Recurrent cholesteatoma was found over the oval window. Follow-up nuclear imaging showed resolution of her osteomyelitis and no evidence of cholesteatoma.

Discussion: Skull base osteomyelitis from Proteus mirabilis is exceedingly rare, with fewer than five case reports available in the worldwide literature. These typically occur in immunocompromised patients with associated cranial neuropathies. Proteus mirabilis can be part of the EAC flora, but is typically found in the GI tract.

We present a case of Proteus mirabilis skull base osteomyelitis in an immunocompetent teenager with minimal symptoms. High-quality CT/MRI images, patient photographs, and the use of intraoperative image guidance for a lateral skull base operation will be presented.