CT imaging of mental nerve neuropathy: the numb chin syndrome.

Abstract

F acial numbness localized to the distribution of the mental nervemental nerve neuritis or mental nerve neuropathy-has been labelled the numb chin syndrome. The inferior alveolar nerve may also be involved. This uncommon neuropathy is almost always unilateral, with anesthesia or hypoesthesia of the chin and lower lip found on physical examination. When not associated with iatrogenic local anesthesia, the condition is most cornmonly due to dental diseases. In the absence of these causes. the condition is clinically significant because of its frequent association with malignant diseases [1-4). In some cases the numb chin syndrome may even be the presenting symptom of an unsuspected malignancy: more frequently it heralds a relapse in a patient with a known neoplasm [1]. In such cases this finding, despite its seemingly clinically benign symptoms, is ominous because it usually implies a grave prognosis [2, 4]. Although painless mental nerve neuropathy may be the only symptom of distant malignant disease, mandibular metastases may be accompanied by paresthesia, pain, local swelling, and bone destruction.