**9. Case report of the patient of brain abscesses caused by MRONJ [34]**

other groups have described an increased incidence of BRONJ who were treated with BPs for longer than 4 years. From these results, AAOMS recommended that, for patients receiving antiresorptive therapy for longer than 4 years and who have low fracture risk but potentially high risk for BRONJ, discontinuation of antiresorptive treatment for approximately 2 months before invasive dental treatment should be considered, in consultation with the physician [5]. Thus, no consensus has yet been reached regarding whether a BP drug holiday before invasive dental treatment is appropriate and neces-

**2.** Suggested dental treatment in patients with cancer and osteoporosis who are receiving BPs

3. Suggested dental treatment in patients with cancer and osteoporosis who are receiving

of time within the 6-month interval to plan for dental treatments [12]. **4.** Discontinuation of antiresorptive therapy after invasive dental treatment

of healing of surgical wounds in the oral cavity.

**5.** Timing of resumption of antiresorptive therapy

For cancer patients with bone metastases, studies have found that the benefits of denosumab are highly superior to those of zoledronic acid [11]. The incidence of DRONJ and BRONJ, however, was found to be similar in patients with cancer [3]. Similar to case of patients treated with BPs, dentists perform conservative dental treatment without drug holiday. Invasive dental treatments, if inevitable, can be conducted without a drug holiday following appropriate infection control. Given that denosumab is administered to osteoporotic patients once every 6 months and the half-life of denosumab is approximately 1 month, there is an ample window

Antiresorptive agents may interfere with the healing of surgical wounds, especially epithelialization [33]. The decision to continue or discontinue antiresorptive treatment must be made jointly by the physician and dentist based on fracture risk, and the status

The time at which to resume antiresorptive administration after a drug holiday is dependent on the balance between the healing of surgical wounds and control of the primary disease. If fracture risk or bone metastasis is well-controlled, resumption of antiresorptive treatment is recommended approximately 2 months after invasive dental procedure, when the damaged alveolar bones are expected to have healed. However, if fracture risk is high or bone metastasis progresses during the drug holiday and resumption of antiresorptive therapy is urgent, it may resume antiresorptive drug with no sign of infection around surgical wounds and epithelialization of the surgical site at 2 weeks after invasive dental treatment, when epithelialization of the surgical site is almost complete, may be the earliest possibility [12].

Dental experts will need to educate patients on the importance of daily oral sanitation, including how to clean the oral cavity after each meal and rinse their mouths with antibacterial mouthwash. Subsequently, dentists begin conservative dental treatment without discontinuation of BPs. In the case that invasive dental treatment such as removal of the teeth responsible for BRONJ is inevitable, however, antibacterial agents will be administered to the patients in advance, and invasive dental treatments should be restricted to the minimum extent and area possible to avoid discontinuation of BP treatment [12].

sary for prevention of BRONJ [12].

denosumab

102 Osteonecrosis

Reports of brain abscesses caused by MRONJ are very rare. The case of a 76-year-old man with terminal-stage prostatic carcinoma and a brain abscess caused by MRONJ at the maxilla with conscious loss is presented here. The zoledronic acid and denosumab were administered for bone metastasis. In the case of maxillary, MRONJ spreads beyond the maxillary sinus into the ethmoid sinus and into the brain. For the brain abscess, an antibiotic regimen based on ceftriaxone and metronidazole and a sequestrectomy contributed to a successful outcome (**Figures 12**–**15**).

**Figure 12.** Intra-oral examination. The 17 was lost naturally 2 months from the first visit and sequester was revealed. The sequester expanded in 8 months from socket.

**Figure 13.** Preoperative CT. Abscess formation is revealed in right maxillary sinus.

**Figure 14.** CT after conscious lost in ER. The absorption image in right frontal lobe is revealed.

**Figure 15.** MRI (T2WI) after conscious lost in ER. Right frontal lobe abscess is depicted.
