Cone beam computed tomography in the differential diagnosis of mental neuropathy (numb chin syndrome) in metastatic colon cancer.

Neuropathy of the mental nerve, also referred to as numb chin syndrome (NCS), is a rare finding that demands for accurate differential diagnosis and therapy. This is a report of two patients with a history of colonic cancer, who experienced a progressive hypaesthesia of one side of the corner of the mouth, lower lip and chin, associated with intermittent phases of pain some weeks prior to admission to hospital. Orthopantomograms were insufficient to disclose the relationship between the osseous lesion and the nerve canal. Cone beam computed tomography (CBCT) clearly disclosed the widely spreading, in-growing tumour of the mandible and the affection of the canal's boundary. CBCT is recommended as the imaging modality of primary choice to disclose apparent osseous affections of the mandibular canal and foramina associated with NCS, in particular in the diagnostics of outpatients admitted to specialized clinics and in the dental office.