[Benign neuropathy of the chin]

A 49-year old man without relevant prior neurological disorder but with overweight, dyslipidaemia and mild glucose dysregulation, noticed on awakening a spontaneous, left-sided and painless numb chin, attributed to isolated mental neuropathy, which regressed entirely within a few weeks. The clinical condition was stable at 1-year follow-up. Ancillary investigations (including electromyography) did not disclose any cause to this episode, notably there was no underlying malignancy or systemic disease. A thorough literature review revealed another similar case which too remained unexplained. The hypothesis of a microvascular neuropathy in relation to vascular risk factors is cautiously raised; such a mechanism has been inferred previously in exceptional cases of regressive mental neuropathy in the context of sickle-cell crisis or systemic vasculitis. Thus, at variance with classical notions, the outlook of the numb chin syndrome is occasionally benign.