Atypical Skull Base Osteomyelitis of the Clivus Mimicking a Malignant Lesion: A Case Report

Background/Objectives: Atypical skull base osteomyelitis (ASBO) is a rare disease, typically involving the basisphenoid and basiocciput. Diagnosis consists of clinical examination, imaging methods such as PET-CT scans and MRI, microbiological testing, and possibly native tissue samples. Long-term intravenous antibiotic therapy is the treatment of choice. Methods/Case Report: We present a case of ASBO of the clivus initially suspected to be a malignant lesion due to malignant melanoma in the patient’s history. Several tissue biopsies were taken, and microbiological testing of native tissue biopsies in combination with PET-CT and MRI imaging led to the diagnosis of ASBO. The patient received long-term antibiotic therapy with meropenem and drastically improved in his overall health. Discussion and Conclusions: This case highlights the challenges encountered in the diagnosis and management of ASBO, especially with relevant possible differential diagnoses.