Numb Chin Syndrome
- Numbness/decreased sensation of the chin and lower lip
- Easily underemphasised by clinicians and patients
- Caused by a wide range of differentials - some associated with significant morbidity and mortality
Epidemiology
- Epidemiology
- ♀ > < = ♂
Clinical Features
- Paraesthesia, dysaesthesia or anaesthesia to chin and lower lip (mental/inferior alveolar nerve region)
- Malignancy tends to be associated with numbness (pain occurs in <10% of cases associated with malignancy)[1]
- Patients with skull based metastasis can also present with other cranial nerve abnormalities
- Patients with mandibular tumours may also present with swelling, loose teeth etc
Differential Diagnosis
- Differential Diagnosis
Aetiology and Pathogenesis
Pathophysiology
- Can occur from a lesion anywhere along the course of the trigeminal nerve (including as proximal as trigeminal ganglion and pons)
- Lesions can be divided into:
- Peripheral lesions - involving mandible, direct nerve infiltration , inflammation or compression
- Central lesions - involving the base of skull, leptomeninges, or brainstem
- Malignancy associated cases can occur through the following mechanisms:
- Direct infiltration of the nerve
- Head and neck primary or metastasis from distant site to mandible
- Leptomeningeal seeding
- Cervical lymphadenopathy
- Nodes in the deeper upper cervical region can exert pressure on the inferior alveolar nerve just before it enters the mandibular foramen[5]
- Paraneoplastic Phenomenon
- Antibodies may be directed against unknown antigens in the nervous system[6]
- Direct infiltration of the nerve
- Aetiology and pathogenesis
Investigations
Laboratory Investigations
Imaging
Other
Management
- Management
Prognosis and Complications
- Prognosis and Complications
Follow-up
- Follow-up
References
- ↑ Galán Gil S, Peñarrocha Diago M, Peñarrocha Diago M. Malignant mental nerve neuropathy: systematic review
- ↑ Lossos A, Siegal T. Numb chin syndrome in cancer patients: etiology, response to treatment, and prognostic significance. Neurology. 1992 Jun 1;42(6):1181-.
- ↑ Rubinstein MK. Cranial mononeuropathy as the first sign of intracranial metastases. Annals of internal medicine. 1969 Jan 1;70(1):49-54.
- ↑ Massey EW, Moore J, Schold SC. Mental neuropathy from systemic cancer. Neurology. 1981 Oct 1;31(10):1277-.
- ↑ Nobler MP. Mental nerve palsy in malignant lymphoma. Cancer. 1969 Jul;24(1):122-7.
- ↑ Raaphorst J, Vanneste J. Numb cheek syndrome as the first manifestation of anti-Hu paraneoplastic neuronopathy. Journal of neurology. 2006 May 1;253(5):664.
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