NUMB Chin Syndrome
Introduction
Numb chin syndrome ( NCS ) also called mental neuropathy , is a rare sensory neuropathy of the mental nerve characterized by numbness, hypoesthesia, paraesthesia, and very rarely pain.
Because the inferior alveolar nerve has no motor fibers, NCS is a purely sensory neuropathy. Common symptoms include numbness over the lower lip, chin, and gingival mucosa; pain is not usually a feature of NCS.
Dental causes, especially iatrogenic ones, maxillofacial trauma, or malignant neoplasm are etiologic factors for this rare syndrome. Compression of the mandibular division of the trigeminal nerve at the base of the skull by a tumor mass or leptomeningeal invasion may also cause NCS.
The most common cause of NCS is breast cancer or lymphoma that has metastasized to the mandible with invasion or compression of the inferior alveolar or mental nerve. Many malignant and metastatic neoplasms are causing this syndrome, like primary osteosarcoma, squamous cell carcinoma, and mandibular metastasis of primary carcinoma of breast, lung, thyroid, kidney, prostate, and nasopharynx. Haematological malignancies like acute lymphocytic leukaemia, Hodgkin and non-Hodgkin lymphoma, and myeloma can cause this neuropathy.
In fact, 47% of cases, numb chin syndrome preceded the diagnosis of the primary tumor.
NCS may be the first manifestation of malignancy or a sign of metastatic disease in a patient with known malignancy, clinicians must be aware that the seemingly trivial symptom of lower facial numbness may signal serious disease.
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| Etiologies Of Numb Chin Syndrome |
Anatomy
The trigeminal nerve has three branches, designated V1, V2, and V3, which provide several sensory and motor functions to the face. The mandibular branch of the trigeminal nerve (V3) exits the skull through the foramen ovale and divides into an anterior motor division that supplies the muscles of mastication and a posterior sensory division that continues through the mandible as the inferior alveolar nerve. The inferior alveolar nerve provides sensory innervation to the gingiva, lower lip, and chin area.
The inferior alveolar nerve exits the mental foramen of the mandible as the mental nerve, which also supplies sensation to the skin of the chin, mucous membranes of the lower lip, and the mandibular gingiva around the incisors.
The inferior alveolar nerve exits the mental foramen of the mandible as the mental nerve, which also supplies sensation to the skin of the chin, mucous membranes of the lower lip, and the mandibular gingiva around the incisors.
Sign And Symptoms
Symptoms of NCS typically include unilateral numbness of the skin of the chin, the lip, and, occasionally, the gingiva.Numbness is usually unilateral, not circumoral as in cases of hyperventilation or hypocalcemia.
Pain and swelling may be present in cases of a locally destructive process such as malignancy or infection. Hypoesthesia or anesthesia is usually present over the chin, lip, and gingiva, but motor function of the lower face is intact.
Percussion-induced pain and loosening of the mandibular teeth may occur in cases of infiltration of the mandibular canal with leukemic cells. If metastatic malignancy is present, patients may have symptoms such as weight loss, fever, fatigue, and pain in addition to symptoms and signs related to the primary tumor. However, symptoms of NCS may precede any other symptoms of malignancy.
Pain and swelling may be present in cases of a locally destructive process such as malignancy or infection. Hypoesthesia or anesthesia is usually present over the chin, lip, and gingiva, but motor function of the lower face is intact.
Percussion-induced pain and loosening of the mandibular teeth may occur in cases of infiltration of the mandibular canal with leukemic cells. If metastatic malignancy is present, patients may have symptoms such as weight loss, fever, fatigue, and pain in addition to symptoms and signs related to the primary tumor. However, symptoms of NCS may precede any other symptoms of malignancy.
Case Report :
Treatment
In general, treatment of the underlying disease causing NCS is the primary mode of therapy. For instance, in cases of dental disease (eg, abscess), primary treatment by a dental consultant is warranted. However, in patients with NCS caused by metastatic cancer, treatment does little to affect outcome; average survival after NCS is diagnosed is approximately 5 months if caused by mandibular metastases and 12 months if leptomeningeal metastases are present. Local radiotherapy has been utilized in patients with skull-base metastases, and cranial irradiation has been used to treat patients with leptomeningeal metastases or carcinomatous meningitis. Mandibular lesions do not typically require local radiotherapy because symptoms.
Numb chin syndrome is a seemingly small complaint that may foretell a serious illness. In an otherwise healthy patient, it should prompt a search for a primary malignancy. In a patient with a known malignancy, it should prompt a search for recurrent and progressive disease.
Source : www.turner-white.com
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