Academic literature on the topic 'Mandibular prognathism'

Mandibular prognathism is one of the most concerning subjects in the oral and maxillofacial fields. In our previous studies, we attempted to clarify the etiology of mandibular prognathism. They revealed that one of the major characteristics of mandibular prognathism was the lower volume/length ratio of the mandibular condyle and body compared to normal, and the masseter muscle showed parallelism with this. This study aimed to evaluate the relationship between mandibular prognathism and the lateral pterygoid muscle by measuring the orientation and volume/length ratio of the lateral pterygoid muscle. Computed tomography was used to calculate the volume/length ratio of the lateral pterygoid muscle in 60 Korean individuals. Mimics 10.0 and Maya version 2018 were used to reconstruct the surface area and surface planes. The results showed that the prognathic group showed smaller lateral pterygoid volume/length ratios compared to the normal group (p < 0.05). In addition, the normal group displayed a larger horizontal angle (p < 0.05) to the mandibular and palatal planes than the prognathic group. This demonstrated that the mechanical drawback of the lateral pterygoid in the prognathic group is associated with mandibular prognathism.

Introduction Mandibular retrognathism is considered to be the most important risk factor for upper airway obstruction. Aim This cross-sectional study intended to examine the relationship between craniofacial morphology and the pharyngeal airway space (PAS) in patients with mandibular retrognathism and mandibular prognathism, when compared to normal subjects. The study also analyzed the influence of mandibular morphology on pharyngeal length (PL). Materials and Methods The PAS was assessed in 92 females (age 15-30 years) further divided into three groups - Group 1- normal mandible (76°≤ SNB ≤82°; n = 31); Group 2-mandibular retrognathism (SNB <76°; n = 31); Group 3-Mandibular prognathism (SNB >82°; n = 30). All subjects were examined by lateral cephalometry with head position standardized using an inclinometer. Craniocervical angulation, uvula length, thickness and angulation were compared among different groups. Results The results showed no statistically significant difference in the pharyngeal airway between the three groups. Measurements of PL showed statistically significant higher values for retrognathic mandible group than normal and prognathic mandible group. Conclusion There is no significant difference between PAS between patients with mandibular retrognathism, normal mandible and mandibular prognathism. Mandibular retrognathism patients show a significantly higher uvula angulation than patients with mandibular prognathism. Craniocervical angulation showed maximum value in retrognathic mandible group followed by normal and prognathic mandible group respectively. Mean PL for retrognathic mandible patients was significantly higher than prognathic mandible patients.

Mandibular prognathism causes functional and esthetic problems. Therefore, many studies have been conducted to understand its etiology. Following our previous study, which revealed that the major characteristic of the mandible with prognathism is the volume/length ratio of the mandibular body and condyle, we analyzed the volume and orientation of the masseter muscle, which inserts into the mandibular body, expecting that the difference in the size of the masseter muscle causes the difference in the mandibular size. This study compared the masseter muscle of the participants in the prognathic group to those in the normal group on the volume/length ratio and orientation. The masseter muscle ratios (volume/length); the angle between the superficial and deep head of the masseter muscle; and the three planes (the palatal, occlusal, and mandibular) were analyzed. A total of 30 participants constituted the normal group (male: 15, female: 15) and 30 patients, the prognathic group (male: 15, female: 15). The results showed that the volume/length ratio of the masseter of the normal group was greater than that of the prognathic group (p < 0.05). In addition, the orientation of both the superficial and deep head of the masseter of the participants in the normal group was more vertical with respect to the mandibular plane than that of the prognathic group (p < 0.05). We concluded that the mechanical disadvantage of the masseter muscle of the prognathic group is attributed to mandibular prognathism.

ABSTRACT Sagittal split ramus osteotomy (SSRO) is commonly used for treatment of mandibular prognathism. This study evaluated masseter muscle activity using electromyography device, in patients with mandibular prognathism before and after bilateral SSRO of the mandible. Twelve prognathic patients (five males and seven females; mean age 20.6 years) were examined. Initial phase of orthodontic treatment was completed in all included patients. Electromyographic activity of masseter muscle was recorded during maximum voluntary clenching as follows: First evaluation: 7 days prior to surgery, second evaluation: 3 months after surgery and third evaluation: 6 months after surgery. Electro-myography quantities were significantly decreased 3 months after surgery. Electromyographic activity of masseter muscle was recovered to the preoperative level 6 months after bilateral SSRO of the mandible. SSRO of the mandible is a safe technique for correction of mandibular prognathism and not seriously affects masticatory muscle electromyographic activity. How to cite this article Eshghpour M, Danesh Sani SA. Electromyographic Analysis of Masseter Muscle after Surgical Correction of Mandibular Prognathism. Int J Head and Neck Surg 2012;3(3):121-124.

Mandibular prognathism is a hereditary condition where there is an excess growth of the mandible in relation to the maxilla that can be associated with maxillary retrusion, mandibular protrusion, or both. Skeletal mandibular prognathism is most prevalent in Eastern Asian populations. This paper focuses on a Korean family with skeletal mandibular prognathism that was inherited through three generations. Apparently, neither mandible nor maxilla is retruded in the affected individuals, but there is a concave facial profile. The dentition has a class I occlusion with skeletal mandibular prognathism, and the only way to treat this case would be orthognathic surgery with the help of orthodontic appliances.

Introduction/Aim. Patients with mandibular prognathism as dominant symptom have disordered sagittal interjaw relations that make prominent appearance to this dental craniofacial anomaly beside hyperplastic mandibles and inverted front teeth overlap. The aim of this study was to examine the differences in dimensions of sella turcica in patients with mandibular prognathism and in eugnathic. Methods. On profile teleradiographs of 30 eugnathic control and 30 patients with mandibular prognathism, three parameters, which represent dimensions of sella turcica, were measured (surface, width and depth). Results. Statistically significant difference in values between the groups was found. All the three measured parameters were significantly higher in the patients with mandibular prognathism (p < 0.01). Conclusion. In the patients with mandibular prognathism all the measured dimensions of sella turcica were bigger, and so was sella turcica, but that enlargement was not in correlation with the degree of anomaly itself.

Background/Aim. The middle part of the face, that is the maxilla, has always been mentioned as a possible etiologic factor of skeletal Class III. However, the importance of the relationship of maxillary retroposition towards the cranial base is still unclear, although it has been examined many times. The aim of this study was to conduct cephalometric analysis of the morphology of maxilla, including the whole middle part of the face in patients with divergent and convergent facial types of mandibular prognathism, as well as to determine differences betweeen them. Methods. Lateral cephalometric teleradiograph images of 90 patients were analyzed at the Dental Clinic of the Military Medical Academy, Belgrade, Serbia. All the patients were male, aged 18-35 years, not previously treated orthodontically. On the basis of dentalskeletal relations of jaws and teeth, the patients were divided into three groups: the group P1 (patients with divergent facial type of mandibular prognathism), P2 (patients with convergent facial type of mandibular pragmathism) and the group E (control group or eugnathic patients). A total of 9 cephalometric parameters related to the middle face were measured and analyzed: the length of the hard palate - SnaSnp, the length of the maxillary corpus - AptmPP, the length of the soft palate, the angle between the hard and soft palate - SnaSnpUt, the angle of inclination of the maxillary alveolar process, the angle of inclination of the upper front teeth, the effective maxillary length - CoA, the posterior maxillary alveolar hyperplasia - U6PP and the angle of maxillary prognathism. Results. The obtained results showed that the CoA, AptmPP and SnaSnp were significally shorter in patients with divergent facial type of mandibular prognathism compared to patients with convergent facial type of the mandibular prognathism and also in both experimental groups of patients compared to the control group. SnaSnp was significantly shorter in patients with divergent facial type of mandibular prognathism compared to the control group, whereas SnaSnp was significantly smaller in patients with convergent facial type of mandibular prognathism compared to the control group. Additionally, there was a pronounced incisor dentoalveolar compensation of skeletal discrepancy in both groups of patients with mandibular prognathism manifested in the form of a significant upper front teeth protrusion, but without significant differences among the groups, while the maxillary retrognathism was present in most patients of both experimental groups. A pronounced UGPP was found only in the patients with divergent type of mandibular prognathism. Conclusion. The maxilla is certainly one of the key factors which contributes to making the diagnosis, but primarily to making a plan for mandibular prognathism treatment. Accurate assessment of the manifestation of abnormality, localization of skeletal problems and understanding of the biological potential are key factors of the stability of the results of surgical-orthodontic treatment of this abnormality.

Orientador: Fausto Berzin
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Objetivos: Avaliar os sinais e sintomas das disfunções temporomandibulares, a dor crônica, a depressão, assim como também avaliar a função muscular dos masseteres e do temporal na mastigação habitual. Todas estas variáveis foram analisadas pré e após cinco anos da cirurgia ortognática. Materiais: Foi utilizado o questionário RDC (reseach diagnostic Criteria), para avaliar e classificar o tipo de disfunção temporomandibular (DTM), assim como para observar o grau de dor crônica e depressão (eixo II), para a análise dos sinais e sintomas das DTMs foi utilizado o eixo I do RDC. Na análise do ciclo mastigatório foi utilizado o eletromiógráfo Myosystem I e software Myosystem BRI, versão 2.52 (DataHominis Tecnologia Ltda). Os músculos avaliados foram a parte anterior do temporal e a parte superficial do masseter de ambos os lados. O comportamento muscular foi avaliado em cinco períodos: pré-cirurgia 2-3 meses (T0); Pós-cirurgia 6 meses (T1), 12 meses (T2), 24 meses (T3) e 60 meses (T4). Resultados: A dor crônica e a depressão apresentaram melhoras após 5 anos do tratamento cirúrgico. Em relação às outras variáveis analisadas, observamos, que após 12, 24 e 60 meses da cirurgia, existe um aumento do tempo e do instante máximo da atividade do ciclo mastigatório. O RMS apresenta o sinal eletromiográfico mais estável após cinco anos do tratamento cirúrgico. Conclusão: A cirurgia ortognatica não é tratamento para as disfunções temporomandibulares. O ciclo mastigatório mostra melhoras no sinal eletromiográfico para pacientes prognatas que não apresentem nenhum tipo de disfunção temporo mandibular
Abstract: Objectives : To evaluate the signs and symptoms of temporomandibular disorders , chronic pain , depression , as well as evaluate the muscle function of the masseter and temporal in mastication . All these variables were analyzed before and five years after orthognathic surgery. Materials : RDC ( reseach diagnostic Criteria) questionnaire was used to assess and classify the type of temporomandibular disorders ( TMD ) , as well as to observe the degree of chronic pain and depression ( axis II ) , for the analysis of the signs and symptoms of the TMD axis I RDC was used . In the analysis of the masticatory cycle Myosystem I electromyography and software Myosystem BRI , version 2.52 ( DataHominis Technology Ltd. ) was used . The muscles tested were the anterior part of the temporal and superficial part of the masseter muscle on both sides . Muscle performance was evaluated in five periods : pre - surgery 2-3 months ( T0 ), 6 months post- surgery ( T1 ) , 12 months ( T2 ) , 24 months ( T3 ) and 60 months ( T4 ) . Results: Chronic pain and depression showed improvement after 5 years of surgical treatment . Regarding the other variables , we observe that 12 , 24 and 60 months after surgery , there is an increase in the time and the maximum moment of the masticatory cycle activity. The RMS has the most stable EMG signal after five years of surgical treatment Conclusion : orthognathic surgery is no treatment for temporomandibular disorders . The masticatory cycle shows improvement in electromyographic signal for prognathic patients without any type of temporomandibular disorders
Doutorado
Anatomia
Doutora em Biologia Buco-Dental

Orientador: Valfrido Antônio Pereira Filho, Márcio de Moraes
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: A configuração e as dimensões da via aérea superior são determinadas pelas estruturas anatômicas como: tecidos moles, musculatura e esqueleto craniofacial, que compõem ou circundam a faringe. As alterações anatômicas dos tecidos moles e/ou do esqueleto craniofacial poderão tornar a via aérea superior (VAS) mais estreita. Estes pontos são os principais fatores etiológicos de um distúrbio cada vez mais diagnosticado na população brasileira conhecida como síndrome da apnéia e hipoapnéia obstrutiva do sono (SAHOS). A cirurgia ortognática, que é utilizada na correção das deformidades dento-esqueléticas, tem se mostrado como o tratamento mais eficiente nos casos graves de SAHOS. Boa parte dos pacientes portadores da síndrome apresenta deformidade dento-esquelética. A síndrome é mais comum nos pacientes portadores de deformidade do tipo classe II. Pacientes com deformidade dento-esquelética de classe III resultante do prognatismo mandibular e/ou deficiência maxilar apresentam uma diminuição da VAS após a cirurgia ortognática de recuo mandibular, embora seja menos tratada na literatura, não deixando claras as consequências dos recuos mandibulares isolados, bem como das cirurgias combinadas de avanço maxilar e recuo mandibular na via aérea superior a longo prazo. Em vista dos fatos apresentados, o presente estudo teve como objetivo avaliar as alterações da via aérea superior em pacientes com deformidade dento-esquelética classe III submetidos à cirurgia ortognática e se há diferença na resposta da via aérea superior quando comparados os gêneros. Para tanto, foi realizada uma avaliação cefalométrica de 45 pacientes divididos em três grupos: grupo 1- cirurgia bimaxilar (23 pacientes); grupo 2- cirurgia de avanço maxilar (15 pacientes) e grupo 3- cirurgia de recuo mandibular (7 pacientes). Desses 45 pacientes, 25 são do gênero masculino e 20 do gênero feminino. A via aérea superior foi avaliada utilizando a análise cefalométrica de Arnett-Gunson FAB-Surgery e o software Dolphin Imaging 11 (Dolphing Imaging and Management Solutions, Chatsworth CA, EUA) em 3 períodos distintos: T0 - pré-operatório; T1 - pós-operatório de 1 semana e T2 - pós-operatório de no mínimo 1 ano. Nos pacientes submetidos à cirurgia bimaxilar houve alteração da VAS no pós-operatório imediato, porém, a longo prazo, a medida da orofaringe voltou ao valor pré-operatório. No grupo 2 existiu um aumento da VAS que se manteve por longo tempo. Nos pacientes submetidos ao recuo mandibular não houve alterações da VAS. Quando se comparou a VAS entre os gêneros, observou-se que tanto os homens quanto as mulheres apresentaram alteração na região da nasofaringe, porém só as mulheres apresentaram uma alteração significativa na aérea da orofaringe. Como conclusão foi possível afirmar que: nos pacientes submetidos à cirurgia bimaxilar o avanço maxilar compensou as alterações na VAS acarretadas pelo recuo mandibular; os pacientes submetidos à cirurgia de recuo mandibular não apresentaram mudanças na VAS; o grupo submetido ao avanço maxilar apresentou um ganho significativo da VAS que se manteve estável pelo período avaliado e que as mulheres registraram alterações na região da nasofaringe e orofaringe, enquanto os homens somente na região da nasofaringe.
Abstract: The configuration and dimensions of the upper airway are determined by the anatomical structures such as soft tissue, muscles and craniofacial skeleton, which comprise or surround the pharynx. Anatomic abnormalities of the soft tissue and/or the craniofacial skeleton may narrow the upper airway leading to obstructive sleep apnea. Class III patients, after orthognathic surgery frequently show a decrease in upper airway which has been less evaluated in the literature. These points are the main factors influencing a disorder increasingly being diagnoses in our population known as obstructive sleep apnea. Orthognathic surgery that is used in the correction of dento-skeletal deformities has been shown to be the most effective treatment in severe cases of obstructive sleep apnea. Many of the patients with the syndrome have dento-skeletal deformities in various degrees. The syndrome is more common in patients with class II deformity. However patients with class III deformity resulting from mandibular prognathism and/or maxillary deficiency after a mandibular setback orthognathic surgery showed a decrease in upper airway which has been less evaluated in the literature. The influence of not making clear the influenced of isolated mandibular setbacks and bimaxillary surgery on the upper airway lacks long-term evaluation. This study aimed to evaluate the changes of upper airway dimensions in patients with class III dento-skeletal deformity treated with orthognathic surgery and the difference in the response of the upper airway between genders. A cephalometric evaluation of 45 patients was performed. The subjects were divided into three groups: group 1 - bimaxillary surgery (23 patients), group 2 - maxillary advancement surgery (15 patients) and group 3 - mandibular setback surgery (7 patients). Of these 45 patients 25 were males and 20 females. The upper airway was evaluated through the cephalometric analysis of Arnett-Gunson FAB-Surgery and the software Dolphin Imaging 11 (Dolphing Imaging and Management Solutions, Chatsworth CA, EUA) in three distinct periods: T0 - preoperative, T1 - one week postoperative and T2 - at least one year postoperative. In patients undergoing bimaxillary surgery we observed changes in the upper airway in the immediate postoperative period, but long-term measures the oropharynx returned to preoperative values. In maxillary advancement there was an increase in the upper airway that remained long-term. In patients who underwent mandibular setback no changes in the upper airway was observed. When comparing the upper airway between the genders we found that both men and women showed abnormalities in the nasopharynx, but only women showed a significant change in the oropharynx area. As conclusion, it was possible to state that: in patients who underwent bimaxillary surgery the jaw advancement compensated the changes of the upper airway brought about by the mandibular setback, the patients who received mandibular setback surgery showed no changes in the upper airway, and the group submitted to maxillary advancement showed a significant increase of the upper airway and that remained stable for the evaluation period. Women had abnormalities in the nasopharynx and oropharynx while men presented abnormalities only in the nasopharynx.
Mestrado
Cirurgia e Traumatologia Buco-Maxilo-Faciais
Mestre em Clínica Odontológica

碩士
高雄醫學大學
牙醫學研究所
89
Mandibular prognathism is characterized by excessive mandibular growth, which may compromise the masticatory function and facial appearance, and this may distort the personality of the patient. Surgical correction of mandibular prognathism will generally improve both the masticatory function and dentofacial aesthetics. This study was undertaken to examine the factors that might be responsible for skeletal stability occurring during one to two years postoperative mandibular setback. Forty-four patients, treated for absolute mandibular prognathism by modified intraoral bilateral vertical ramus osteotomy, were evaluated cephalometrically at least 1-year postoperatively. A set of 7 standardized lateral cephalograms were obtained from each subject, i.e., preoperative (T1) and immediately postoperative (T2), prior to removing the maxillomandibular fixation (T3), 3 months (T4), 6 months (T5), 1-year (T6) and 2-years postoperative (T7). There were 20 patients who underwent a 2-year follow-up with cephalograms. The mean setback of the menton was 12.3mm in the horizontal direction and 0.8mm downward in the vertical direction. Relapse was defined as forward movement of the menton during the 2-year postoperative period. The average movement for 1-year follow-up (12 of 20 patients) in the horizontal direction was as follows; 4 with 2.1mm (16% = 2.1/13.1) in forward movement and 8 with 1.6mm (12.4% = 1.6/12.9) in backward movement. The average movement during the 1-year follow-up (12 of 20 patients) in the vertical direction was 7 patients with 1.5mm in upward movement and 8 with 0.7mm in downward movement. The average movement during the 2-year follow-up (20 patients) in the horizontal direction was as follows; 14 with 2mm (16.3% = 2/12.3) in forward movement and 5 with 1.4mm (12.1% = 1.4/11.6) in backward movement. The average movement during the 2-year follow-up (20 patients) in the vertical direction was as follows; 11 patients with 1.7mm in upward movement and 8 with 1.2mm in downward movement. The variables included vertical and horizontal Me (T21) distance, Rp-Cut (distance between osteotomy point and the most posterior point of inferior ramus)(T1), and area of the pterygomasseteric sling (Rp-Cut-H ×V-T1) The multiple regression showed that the vertical amount of setback (T21) that predicated the vertical relapse (T72) was significant, whereas no significant correlations were noted between the variables and horizontal relapse (T72). In patients whose distal segments were still in the backward group 2-years postoperaviely, their osteotomy positions were anterior to the forward group. This tell us: the more anterior osteotomy position the more acceptable capacity of the pterygomasseteric sling will be created and this allow the distal segment to setback more without distend the pterygomasseteric sling. These results suggest that this technique can provide greater acceptable capacity for larger amount of distal segment setback and is feasible for the correction of severe mandibular prognathism. Key Words: Postoperative Stability, Mandibular Prognathism Modified Intraoral Vertical Ramus Osteotomy

碩士
國立臺灣大學
臨床牙醫學研究所
96
Purpose The purpose of this retrospective study was to compare post-operative changes and skeletal stability between bilateral saggital split ramus osteotomy (BSSO) and intraoral vertical ramus osteotomy (IVRO) used for mandibular setback. Factors contributing to skeletal instability were also identified. Patients and Methods The study included 48 patients with mandibular prognathism, who underwent mandibular setback surgery at the Department of Oral and Maxillo-facial Surgery, National Taiwan University Hospital (NTUH) from January 2001 to December 2006. Twenty-five of them recieved with rigid internal fixation, the remaining 23 underwent IVRO with intermaxillary fixation. Lateral cephalometric radiographs were taken within 1 month before surgery (T1), immediately after the operation (within 1 week, T2), and at the time of completion of post-op orthodontic treatment (T3). The T1,T2, and T3 radiographs were traced and superimposed with “best-fit” technique and the data were digitalized to analyze the changes at T2-T1 and T3-T2. Mann-Whitney test was used to verify the differences in post-operative changes and long-term skeletal stability between the two groups. And the linear regression model was established to find the contributing factors. Results The mean amount of horizontal setback at pogonion was 6.55 mm in BSSO group and 9.68 mm in IVRO group. The mean amount of vertical movement at menton was 0.99 mm upward in BSSO group and 0.12 mm downward in IVRO group. Long-term observation (T3-T2) showed that the chin moved upward (1.10 mm) and forward (1.48 mm) after BSSO, and moved downward (0.32 mm) and backward (1.19 mm) after IVRO. Significant differences were noted between the two procedures in horizontal skeletal instability at pogonion (T3-T2, p=.002), and vertical skeletal instability at menton (T3-T2, p=.004). In BSSO group, the horizontal soft/hard tissue ratio was 1.06 at B point, 0.88 at pogonion, 1.04 at menton. And the vertical soft/hard tissue ratio was 0.97 at B point, 1.00 at pogonion, 0.57 at menton. In IVRO group, the horizontal soft/hard tissue ratio was 1.03 at B point, 0.88 at pogonion, 1.01 at menton. And the vertical soft/hard tissue ratio was 0.91 at B point, 1.00 at pogonion, 2.07 at menton. No significant difference was found in the soft/hard tissue ratio. In BSSO group, the significant predictor for the horizontal skeletal instability was age and rotation of condylar axis. For vertical skeletal instability, it was significantly correlated to change of mandibular plane angle. In IVRO group, the significant predictors for horizontal skeletal instability were gender, openbite, and jaw deviation. And vertical skeletal instability was significantly correlated to age, amount of horizontal setback, grade of openbite, and follow-up period. Discussion The patterns of post-operative instability are significantly different between BSSO and IVRO. The key factors contributing to this difference was considered be the change in condylar axis and the application of RIF or IMF. In BSSO, the tooth-bearing segment was rigidly fixed with the bilateral condylar segments. Therefore, the chin moves upward and forward as the condylar axis rotates counter-clockwise post-operatively. But in IVRO, osseous remodeling takes place at the osteotomy site. The chin may not move while the condylar axis rotates counter-clockwise post-operatively. Moreover, the application of IMF will lead to an increase of lower facial height. Thus, the chin moves downward and backward after the surgery.

Klinefelter syndrome (KS) was first identified by Dr. Harry Klinefelter in 1942 (Klinefelter, Reifenstein, and Albright 1942) in a report of nine tall men with hypogonadism, sparse body hair, gynecomastia, and infertility. The associated chromosome disorder 47XXY was identified several years later (Jacobs and Strong 1959). The full phenotype consists of hypogonadism, low testosterone levels, infertility, gynecomastia, sparse body hair, eunuchoid body habitus, long legs and arm span, and above-average height. However, except for hypogonadism (small testes), which is present in nearly all individuals with XXY, the physical phenotype may be quite variable. In live-born males, KS has an incidence of 1:500 to 1:1,000 (Bojesen, Juul, and Gravholt 2003; Hamerton, Canning, Ray, and Smith 1975; Ratcliffe, Bancroft, Axworthy, and McLaren 1982; Rovet, Netley, Keenan, Bailey, and Stewart 1996), with a further incidence of 1:300 in spontaneous abortions (Hassold and Jacobs 1984). Klinefelter syndrome is the most common of the sex chromosome abnormalities and the second most common chromosomal disorder after Down syndrome. The possibility that incidence is increasing has also been raised (Morris, Alberman, Scott, and Jacobs 2008). Despite this, possibly as a consequence of poor identification, the syndrome has been studied less extensively than, for example, Turner syndrome (45XO) and many other developmental disorders. Boys with KS are generally tall and long-limbed but with increasing height in the population, these characteristics alone are not necessarily distinguishing. Individuals with KS are generally not immediately identifiable, and many cases of KS remain unidentified throughout life. Up to two-thirds of cases may never be identified clinically (Lanfranco, Kamischke, Zitzmann, and Nieschlag 2004). There is no clearly identifiable facial appearance, although mandibular prognathism (a prominent lower jaw and extended chin) is reported on group analysis using radiographic cephalometry (Brown, Alvesalo, and Townsend 1993). Increased genetic screening now means that 10% of cases in the United Kingdom are diagnosed prenatally on the basis of karyotype, with a further 25% of cases diagnosed during childhood (Abramsky and Chapple 1997). However, this means that 65% of cases reach puberty undiagnosed. In Belgium, fewer than 10% of expected cases are diagnosed before puberty (Bojesen et al. 2003).