Pseudomonal Osteomyelitis of the Anterior Skull Base: Case Report and Review of the Literature

Background: Skull base osteomyelitis (SBO) is a rare, life-threatening infection of the bone caused by either bacterial or fungal pathogens and most commonly associated with patients in immunocompromized states. Some reports have highlighted only 8.4 cases per year. SBO has a mortality rate of around 10% and a recurrence rate of 10 to 15%. Studies have reported similar incidence rates of fungal (52%) and bacterial (48%) etiologies for all types of SBO. However, the profile of causative organism changes drastically by anatomical site. For example, temporal SBO is commonly caused by Pseudomonas aeruginosa (90–98% incidence), often as a complication of otitis externa in diabetes mellitus patients. Meanwhile, central skull base osteomyelitis has a more diverse distribution, with Staphylococcus aureus (21%), Pseudomonas aeruginosa (19%), and all fungal sources (17%) as the most common pathogens. Here, we present a case of a patient with Pseudomonal SBO and review the literature to raise awareness of this uncommon clinical entity.

Case: In this report, we describe the case of a 51-year-old patient with a history of chronic lymphocytic leukemia complicated by chemotherapy-induced neutropenia, treated for Pseudomonal SBO. He presented with persistent nasal drainage and right sided facial and eye pain. Treatment included bone marrow stimulants for his neutropenia, multiple rounds of surgical debridement and removal of necrotic bone, and intravenous antibiotic and antifungal therapy. Cultures were conducted following surgical intervention to obtain identification of the causative organism and obtain antimicrobial sensitivities. After identifying that the source was Pseudomonas aeruginosa, culture-directed antibiotics were modified accordingly, with persistent prophylactic antimicrobial therapy due to the patient's immunocompromized state.

Discussion and Conclusion: Pseudomonal SBO is a rare and potentially life-threatening condition that is clinically indistinguishable from fungal etiologies. Compared with other bacterial etiologies of SBO, Pseudomonal SBO is associated with higher recurrence rates, increased likelihood of treatment failure, and decreased overall prognosis. Due to the aggressive nature of the disease, rapid empiric therapy and subsequent tissue biopsy with culture and sensitivities is recommended. After initial empiric treatment, rapid identification of the causative microorganism is suggested, as the evidence surrounding surgical resection is equivocal in cases of bacterial SBO, but is widely recommended in fungal etiologies. Following biopsy and surgical resection (if indicated), long-term intravenous antibiotics for 6 months duration tailored to microorganism's sensitivities is recommended in both bacterial and fungal etiologies to reduce the risk of infection recurrence. In immunocompromized patients with neutropenia, especially those post-chemotherapy, therapies that increase absolute neutrophil counts are also advised to improve chances for complete resolution of SBO. Through this case and literature review, we conclude that early diagnosis and subsequent aggressive treatment, both surgical and medical, are necessary for patients with suspected SBO to reduce the potentially life-threatening complications associated with the condition.

Fig. 1 Computed tomography showing right lamina papyracea multifocal dehiscence (red arrow) with intraorbital extension of disease, resulting in proptosis (white arrow). There is right anterior skull base dehiscence (green arrow), which raises suspicion for intracranial extension of disease.

Fig. 2 Timeline of events.