Summary

Numb chin syndrome (NCS) is a rare yet potentially ominous sensory neuropathy characterised by unilateral hypoesthesia or paraesthesia over the lower lip, chin and occasionally gingival mucosa. Recognising NCS clinically is important as this may be a subtle sign of occult malignancy progression or relapses. Current expert opinion is that patients with NCS without apparent cause should be assumed to have a malignant aetiology until proven otherwise. By far the most common non-haematologic neoplastic cause of NCS is breast cancer, while the most common haematologic neoplastic cause is non-Hodgkin lymphoma (NHL). The pathophysiology of NCS has been shown to be either direct compression of the mental nerve by tumour mass, leptomeningeal invasion or a bony lesion at mental foramen. Here we report a case of NHL presenting with NCS with no evidence of metastasis in brain parenchyma, cerebrospinal fluid or mandibular bone. Instead, diffuse dural thickening and focal lesion in clivus were identified. We propose that these may represent novel mechanisms of NCS.