Skull Base Osteomyelitis and Bone Defect Induced by Anti-Resorptive Agent-Related Osteonecrosis of the Jaw in the Mandible: A Case Report

A 57-year-old woman with a history of breast cancer and bone metastasis was referred to our hospital for pain following bone exposure surrounding the right molar teeth. As computed tomography (CT) revealed a periosteal reaction in that region, the condition was diagnosed as stage 2 anti-resorptive agent-related osteonecrosis of the jaw (ARONJ). She desired conservative therapy, not curative surgical therapy. However, ARONJ progressed with skin fistula formation in the external auditory canal and submandibular region, and more bacterial temporomandibular arthritis occurred. Twenty-five months later, she was admitted to the emergency department of our hospital for headache and fever. CT and magnetic resonance imaging revealed osteomyelitis of the temporal bone and extradural and brain abscess formation in the middle cranial fossa. Antibiotics were administered and craniotomy with drainage was performed, and the symptoms improved immediately after drainage. Ninety months after the diagnosis, mandibular bone exposure has increased markedly, and the temporal bone of the middle skull base shows a bone defect. This study suggests that ARONJ has the potential to lead to multiple complications.