A Case of Masticatory Muscle Interstitial Abscess Secondary to Medication-related Osteonecrosis of the Jaw

Abstract

This was a case of an 80-year-old woman, who presented to the clinic with the chief complaint of left jaw pain. CT showed erythema and swelling from the left temporal region to the left mandibular angle, and hypointense shadows mainly inside the temporalis muscle and masseter muscle along the perimandibular branch from the left temporal region to the mandibular angle. The margins were accompanied by contrast effect, and the patient was admitted to the hospital with a diagnosis of masticatory muscle space abscess. The patient also had a history of treatment with denosumab for bone metastasis from a previous left breast cancer, and bone exposure in the right lower central incisor and left upper lateral incisor, which was also associated with medication-related osteonecrosis of the jaw (MRONJ). The patient was treated with antimicrobial agents and incisional drainage and daily washing, and although improvement was observed, a small amount of pus continued to drain. Considering the patient’s wishes, the antimicrobial agents were changed to oral administration, and the patient was followed up on an outpatient basis.

In this case, the MRONJ was accompanied by a masticatory muscle abscess, and the treatment period required for the MRONJ-associated masticatory muscle abscess was longer than that for a masticatory muscle abscess without MRONJ. The duration of antimicrobial therapy was long and the course of treatment may be refractory. With the development of drug therapy for cancer treatment, long-term survival is now possible in many carcinomas. The number of patients with bone metastases treated with anti-RANKL monoclonal antibody products is expected to increase in the future. Thus, it is necessary to be aware of MRONJ and be cautious in the treatment of such patients.