Numb Chin Syndrome in Nasopharyngeal Cancer Patients Demonstrated by Bone Scan: Report of Two Cases

Abstract

The numb chin syndrome (NCS), also referred to as mental neuropathy, is characterized by numbness and hypoesthesia confined to the chin and lower lip. We presented two patients with nasopharyngeal cancer (NPC) who had received operation and radiotherapy. Numbness feeling developed around the chin of both patients. The whole body bone scans showed increased (superscript 99m)Tc-MDP uptake around the mandible, which was consistent with bone metastasis. Literatures regarding NCS demonstrated by the bone scan were reviewed. Breast cancer alone accounts the most common cases of NCS in patients with malignancy. Other malignancies associated with the NCS include lymphoma, carcinomas of the lung, thyroid and kidney, and various leukemias. When NCS is presented in patients with malignancy, a whole body bone scan can help in detecting bony metastasis and treatment planning. However, the extraction of the maxillary posterior teeth to prevent dental osteoradionecrosis may cause the same bone scan pattern, interpretation of the picture of numb chin syndrome thus should be cautious. Clinical status, radiographies and dental records are helpful in differential diagnosis.