Mental neuropathy (numb chin syndrome) leading to diagnosis of metastatic mediastinal cancer.

Neuropathy of the mental nerve is a rare condition that demands accurate differential diagnosis. A 69-year-old male experienced progressive hypoaesthesia of the right side of the corner of the mouth and chin, associated with intermittent phases of pain. Plain radiographs and computerised tomography (CT) scans revealed the mental foramen on the top of the toothless mandible and a symmetrically depicted mandibular canal. Surgical exploration demonstrated a tumour inside the mandibular canal, not visible on radiographs. Subsequently performed CT scans revealed an extensive mediastinal tumour with metastasis to multiple lymph nodes and further metastases to the kidney and liver. Diagnosis was small-cell bronchial carcinoma (extensive disease, stage grouping II B, Marburg classification). Palliative chemotherapy was ineffective and the patient died with evidence of tumour progression. The cause of a numb chin needs to be clarified further, and the syndrome should be seriously considered, using thorough diagnosis, including the surgical revision of the affected nerve.