Teaching NeuroImages: "numb chin syndrome" in a patient with breast cancer.

A51-year-old woman with breast cancer presented with progressive numbness and burning in the right lower gum and oral mucosa. Neurologic examination was normal except for reduced sensation in the right lower gum region. Inferior alveolar neuropathy from mandible metastasis was diagnosed (figures 1 and 2). “Numb chin syndrome” is characterized by decreased sensation in the chin or lower lip, oral mucosa, and gum. Median time from cancer diagnosis is 45.8 6 51 months. Median age is 48 years. It occurs in a variety of cancers, most commonly breast. Sites of neoplastic trigeminal nerve compression/infiltration include the skull base, leptomeninges, or mandible, the latter affecting the mental or inferior alveolar branches. Prompt diagnosis and treatment of the metastasis, typically with radiation therapy, can improve neurologic symptoms.