Abstract
Numb chin syndrome (NCS) refers to a rare sensory neuropathy characterized by numbness of the chin within the distribution of the mental or inferior alveolar nerve. Although NCS is usually caused by a benign process, it should not be underestimated and a thorough diagnostic evaluation for a new or known progressive malignancy should always be performed. Here, we report a case of salivary ductal adenocarcinoma that mimicked a pulpitis and periodontitis in its early presentation accompanied by numbness of chin. The course and diagnosis of this case are discussed, and a brief review of the literature is presented. It is hoped for clinicians to keep the malignant possibility of NCS in mind and take a thorough examination.
Highlights
Numb chin syndrome (NCS), often synonymously named as “mental nerve neuropathy,” is a sensory neuropathy characterized by numbness or, very rarely, pain of the chin and lower lip within the mental or inferior alveolar nerve distribution
The mandibular division of the trigeminal nerve, after exiting the skull base through the foramen ovale, branches into the inferior alveolar nerve passing through the mandible canal, and exits at the mental foramen as the mental nerve
The diagnostic process may require thoracic or abdominal radiographs, sonography, and, if needed, abdominal computerized tomography (CT) scans and Magnetic resonance imaging (MRI), positron emission tomography combined with computed tomography (PET-CT) scans to look for primary neoplasm and its metastatic sites [6, 24]
Summary
Numb chin syndrome (NCS), often synonymously named as “mental nerve neuropathy,” is a sensory neuropathy characterized by numbness (hypoesthesia, paresthesia, dysesthesia, and anesthesia) or, very rarely, pain of the chin and lower lip within the mental or inferior alveolar nerve distribution. Most cases are caused by odontogenic diseases such as trauma, dental extraction, dentoalveolar abscess, and osteomyelitis [1, 2]. This innocuous complaint is sometimes considered as a “red flag” symptom of an incipient malignancy or an indication of the spread of an established tumor. Compared to intraoral mucosal malignancies, NCS does relate more to metastatic tumors. Intraoral mucosal malignancies, such as squamous cell carcinoma of the oral mucosa or lip or cancer of the small salivary glands, are usually associated with typical mucosal signs, for example, ulceration with raised margins, lumps with abnormal vessels, or abnormal swellings. In this paper, aimed to highlight that NCS might lead to severe conditions and to show how the diagnosis was made, we reported a case with an initial character of NCS that was confirmed as a mandible malignancy originating from salivary duct adenocarcinoma and reviewed the causes, the possible mechanism, the diagnostic approaches, and differential diagnosis of NCS
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