(A840) Local Antibiotic Therapy Using Calcium Sulfate in Lateral Skull Base Osteomyelitis: A Case Series

Introduction: Skull base osteomyelitis (SBO) is a severe condition with a high mortality rate in cases involving cranial nerve palsy. The treatment of SBO presents significant challenges due to anatomical limitations that complicate surgical debridement and the restricted efficacy of systemic antibiotic therapy. We report initial experiences using calcium sulfate, a resorbable antibiotic carrier, as a long-term local adjuvant therapy in conjunction with surgical management for the treatment of SBO.

Methods: Four cases of lateral SBO secondary to otitis externa were treated with a multimodal approach from December 2023 to October 2024. Preoperative cranial nerve involvement was observed in two patients, presenting as facial nerve palsy, with one case additionally showing hypoglossal nerve palsy. One patient developed a salivary fistula at the floor of the auditory canal, while another experienced extension of malignant otitis externa to the temporomandibular joint. Complementary to a systemic antibiotic therapy with Piperacillin/ Tazobactam i.v., individualized surgical debridement and defect coverage using gentamicin-impregnated calcium sulfate were performed. Subsequently, the patients received Ciprofloxacin p.o.. Outcomes were evaluated through clinical findings and erythrocyte sedimentation rate (ESR).

Results: The mean follow-up period was 6 months [Range: 3-13 months] from December 2023 to January 2025, with an average patient age of 77,5 years. Postoperatively, preexisting cranial nerve deficits showed partial to full resolution, and the ESR has decreased. No complications related to the calcium sulfate carrier, such as wound healing disorders or abnormal serum calcium levels were observed. Functional diagnostics ruled out gentamicin-induced ototoxicity. All patients have remained free of recurrence to date.

Conclusions: The combination of surgical debridement and the application of antibiotic-impregnated, resorbable calcium sulfate may become an integral component, alongside systemic antibiotic, in the management of SBO by enabling localized, long-term antibiotic delivery.