Numb Chin Syndrome — ORE Part 1 MCQ

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HardOral MedicineNumb Chin SyndromeORE Part 1

A patient reports progressive unilateral numbness of the lower lip and chin for 3 weeks. There has been no recent dental treatment, local anaesthetic injection, facial trauma, dental pain or clinical evidence of odontogenic infection. What is the most important diagnosis to exclude?

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Correct answer: D — Malignant infiltration of the mental or inferior alveolar nerve

Explanation lettering: E = shown as A · D = shown as B · A = shown as D · B = shown as E

A is correct. Progressive unilateral sensory loss in the mental nerve distribution, without a dental, traumatic or iatrogenic cause, is numb chin syndrome and warrants exclusion of malignancy. It may reflect metastatic disease or primary/haematological malignancy involving the mandible, inferior alveolar nerve, skull base or leptomeninges. UK dental literature recommends urgent investigation and referral when this presentation has no odontogenic explanation. Facial nerve palsy causes motor weakness, not isolated lower-lip/chin anaesthesia. Trigeminal neuralgia is characterised by brief paroxysms of facial pain rather than persistent sensory loss. Odontogenic infection remains a differential, but the stem specifically excludes pain and clinical evidence of infection. Vitamin B12 deficiency more typically produces a diffuse peripheral neuropathy, not an isolated unilateral mental neuropathy.

Reference: Ryba F, Rice S, Hutchison IL. Numb chin syndrome: an ominous clinical sign. British Dental Journal. 2010;208:283-285. https://pubmed.ncbi.nlm.nih.gov/35644699/