Accuracy in the diagnosis of the mental nerve loop: a comparative study between panoramic radiography and cone beam computed tomography / Precisión en el diagnóstico del bucle del nervio mental: estudio comparativo entre radiografía panorámica y tomografía computadorizada de haz cónico

Dental implant and chin osteotomy are executed on the mandible body and the mental nerve is an important anatomical limit. The aim of this research was to know the position of the mental nerve loop comparing result in panoramic radiography and cone beam computed tomography. We analyzed 94 hemimandibles and the patient sample comprised female and male subjects of ages ranging from 18 to 52 years (mean age, 35 years) selected randomly from the database of patients at the Division of Oral Radiology at Piracicaba Dental School State University of Campinas; the anterior loop (AL) of the mental nerve was evaluated regarding the presence or absence, which was classified as rectilinear or curvilinear and measurement of its length was obtained. The observations were made in the digital panoramic radiography (PR) and the cone beam computed tomography (CBCT) according to a routine technique. The frequencies of the AL identified through PR and CBCT were different: in PR the loop was identified in 42.6% of cases, and only 12.8% were bilateral. In contrast, the AL was detected in 29.8% of the samples using CBCT, with 6.4% being bilateral; Statistical comparison between PR and CBCT showed that the PR led to false-positive diagnosis of the AL in this sample. According to the results of this study, the frequency of AL is low. Thus, it can be assumed that it is not a common condition in this population.

Implantes dentales y la osteotomía de mentón son realizadas en el cuerpo mandibular y el nervio mental es un importante limite anatómico. El objetivo de esta investigación es conocer la posición del bucle del nervio mental comparando resultados entre radiografia panorámica y tomografía computadorizada de haz cónico (TCHC). Fueron analizadas 94 hemimandíbulas; la muestra de pacientes de sexo feminino y masculino con edades fluctuando entre 18 y 52 años (edad media, 35 años) seleccionados de la base de datos de pacientes de la División de Radiología de la Facultad de Odontología de Piracicaba, Universidad Estadual de Campinas; el bucle anterior (BA) del nervio mental fue evaluado según su presencia o ausencia, el cual fue clasificado como rectilíneo o curvilíneo obteniéndose el largo total del bucle; las observaciones fueron realizadas en radiografías panorámicas digitales (RP) y en TCHC de acuerdo a técnicas de rutina. La frecuencia de identificación del BA en RP y TCHC fue diferente: en la PR, el BA se identificó en un 42,6% de los casos y solo el 12,8% fue bilateral. En contraste, el BA fue detectado en el 29,8% de la muestra utilizando TCHC, con un 6,4% bilateral; la comparación estadística entre RP y TCHC muestra que la RP lleva a diagnósticos falsos positivos de la muestra de BA. De acuerdo con los resultados de este estudio, la frecuencia de BA es baja. Por este motivo se puede asumir que esta es una condición anatómica poco frecuente en la población estudiada.

Numb chin syndrome: A case report and review of the literature.

Numbness of the lower lip, the skin of the chin, or the gingiva of the lower anterior teeth secondary to various dental diseases is a common manifestation that is largely underappreciated. The association of numb chin syndrome (NCS) with serious disease like metastatic malignancy and systemic conditions is frequent enough to warrant a search for these possible etiologies. In this paper we report a case of NCS that occurred secondary to malignant disease; we discuss our findings with special emphasis on metastatic malignancies leading to NCS, when the survival is only for a few months.

Numb chin syndrome as a manifestation of metastatic squamous cell carcinoma of esophagus.

Numb chin syndrome (NCS) is a sensory neuropathy presenting with numbness of the chin in the distribution of the mental nerve and the branches of the mandibular division of the trigeminal nerve. Though it can be caused by a benign process, NCS should be regarded as being due to malignancy until proven otherwise. Among the malignancies that cause NCS the most common are breast cancer, prostate cancer, and lymphoreticular malignancy. In squamous cell carcinoma (SCC) of the esophagus, spread to the mandible is a rare and often late event. An often overlooked clinical sign in mandibular metastases is hypoesthesia or paresthesia over the peripheral distribution of the inferior alveolar nerve/mental nerve; this sign has been referred to in the literature as NCS or numb lip syndrome or mental nerve neuropathy. Rarely, this may be the first presentation of a disseminated malignancy. Prognosis is usually poor. The discovery of this symptom should alert the clinician to the possibility of disseminated disease. In this article we report a rare case of metastatic SCC of the esophagus in a 40-year-old male patient who presented with NCS. We also review the mechanism, causes, and evaluation of NCS.