[Numb chin syndrome caused by biphosphonates-induced osteonecrosis of the jaw]

Numb chin syndrome is caused by a mental or inferior alveolar nerve neuropathy. Traumatic and infectious injuries are the most frequent causes of the syndrome but, if an evident cause does not exist, a neoplastic etiology must be investigated. Other causes of the numb chin syndrome are rare.

A 73-year-old woman had had a diagnosis of metastatic breast cancer and was been treated with zoledronic acid. She attended because of hypoesthesia and dysesthesia of the chin congruent with mental nerve distribution. A computed tomography of the jaw showed an osteolytic lesion with central bone sequestration, so biphosphonate-induced osteonecrosis of the jaw was diagnosed. After zoledronic acid was withdrawn, clinical neuropathy and imaging findings remained stable.

Biphosphonates-induced osteonecrosis of the jaw is a recently described condition. It has been rarely reported as a cause for numb chin syndrome. In the future, osteonecrosis of the jaw must be considered in the differential diagnosis of this syndrome in cancer patients treated with biphosphonates.