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Numb chin syndrome as the presenting symptom of carcinomatous meningitis
The numb chin syndrome (NCS) is a rare neurological condition which origins in the absence of a dental cause and is most often associated with malignancy [1–5]. Patients develop orofacial paraesthesia typically localized to the chin and lower lip.We present a series of four female patients (mean age = 66.2 years) who had been diagnosed with breast cancer and were complaining of orofacial numbness associated with neuralgia involving the chin and the lower lip. In one case, there was associated paralysis of the facial nerve. At the onset of the condition, the symptoms were monolateral but in one case, as the disease was progressing, the numbness involved the controlateral mental region.
Three patients were on treatment with i.v. bisphosphonates for their bone metastases, while the fourth subject had been treated with taxolo and, subsequently, with fulvestrant obtaining a good control of her disease.
Examination revealed an area of spontaneous paraesthesia in the distribution of the mental nerve, but no dental or periodontal lesions associated with the described symptoms.
In all patients, a digital panoramic radiograph and a computed tomography (CT) scan were taken and they both excluded a dental problem or a mandibular lesion as the origin of the numbness. Our patients were all having regular bone scans to monitor the neoplastic involvement; in all cases, they did not show abnormal metabolic activity of the jaws. In all patients, the gadolinium-enhanced magnetic resonance imaging (MRI) showed thickening of meninges.
For three patients, the analysis of the cerebrospinal fluid (CSF) revealed either the presence of carcinomatous cells or increase in proteins level and decrease in glucose concentration. The neurological examination, combined with the radiological features and the CSF analysis, confirmed the diagnoses of carcinomatous meningitis.
Table 1 summarises the clinical features of our patients.
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The NCS is an underappreciated though well-documented manifestation of neurological metastases.
A frequent aetiology is malignant infiltration or compression of the mental or inferior alveolar nerve by jaw metastases or local tumour [1]. NCS may also be caused by metastases to the base of the skull. Involvement of the leptomeninges is an uncommon feature, though estimation of its prevalence may be low due to underdiagnosis.
If mandibulare lesions are excluded by CT scan and scintigraphy, penetration of the dura and involvement of the leptomeninges or cerebral malignancy should be suspected and then confirmed by an MRI.
NCS has a better prognosis if it depends on leptomeningeal involvement compared with mandibular metastases. This is why it is important not only the recognition of the syndrome, but also its attribution to a causal factor.
Though rare, the NCS may be the first symptom in the presentation of an underlying malignancy. As an early diagnosis can have a significant improvement of treatment course and prognosis, we emphasise that dentists and physician should consider metastatic cancer in patients presenting with NCS in the absence of other local causes.
* E-mail: m.biasotto{at}fmc.units.it
References
1. Burt RK, Sharfman WH, Karp BI, Wilson WH. Mental neuropathy (numb chin syndrome). A harbinger of tumor progression or relapse. Cancer (1992) 70:877–881.[CrossRef][Web of Science][Medline]
2. Lossos A, Siegal T. Numb chin syndrome in cancer patients: etiology, response to treatment, and prognostic significance. Neurology (1992) 42:1181–1184.
3. Turner-Iannacci A, Mozaffari E, Stoopler ET. Mental nerve neuropathy: case report and review. Can J Emerg Med (2003) 5:259–262.
4. Baskaran RK, Krishnamoorthy, Smith M. Numb chin syndrome—a reflection of systemic malignancy. World J Surg Oncol (2006) 4:52.[CrossRef][Medline]
5. Laurencet FM, Anchisi S, Tullen E, Dietrich PY. Mental neuropathy: report of five cases and review of the literature. Crit Rev Oncol Hematol (2000) 34:71–79.[CrossRef][Medline]
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