|Year : 2012 | Volume
| Issue : 3 | Page : 237-241
Detection of orbicularis oris muscle defects in first degree relatives of cleft lip children using ultrasound
M Mittal1, N Maheshwari1, K Ahlawat2, V Sharma2, A Sultan3, R Chopra1
1 Department of Pediatric Denistry, SGT Dental College, Gurgaon, Haryana, India
2 Department of Radiology, Medanta, Medicity, Gurgaon, India
3 Department of Pediatric Dentistry, Jamia Milia Ismalia Dental College, New Delhi, India
|Date of Web Publication||21-Dec-2012|
A-29, Ground Floor, Hauz Khas, New Delhi - 110 016
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Objective: The severity of cleft lip (CL) varies considerably from complete bilateral CL and palate at one end of the spectrum to a minimal CL at the other. In some cases of microform clefting, there may be no visible manifestation of the defect on the lip surface (i.e., the defect is occult) and no residual functional deficit. This study used high resolution ultrasonography to detect subclinical anomalies of orbicularis oris muscle (OOM) in first degree relatives of CL +- cleft palate children and compared it with controls. Materials and Methods: Thirty relatives of 25 children with non-syndromic CL or CL+ CP were identified for the study. Thirty subjects having negative family history of CL/P in three generations and absence of any minimal cleft features were taken as controls. Ultrasound scans of OOM of all the controls and relatives were taken. Statistical analysis was performed using standard χ2 tests with Yates correction. Results: Defects were seen in 13.3% of relatives and no defects were seen in controls, this was not statistically significant. Conclusion: The data support the hypothesis that subclinical CL cases with subepithelial OOM defects do exist and Orbicularis oris discontinuities represent the mildest form of CL.
Keywords: Cleft lip, orbicularis oris muscle, Ultrasound
|How to cite this article:|
Mittal M, Maheshwari N, Ahlawat K, Sharma V, Sultan A, Chopra R. Detection of orbicularis oris muscle defects in first degree relatives of cleft lip children using ultrasound. J Indian Soc Pedod Prev Dent 2012;30:237-41
|How to cite this URL:|
Mittal M, Maheshwari N, Ahlawat K, Sharma V, Sultan A, Chopra R. Detection of orbicularis oris muscle defects in first degree relatives of cleft lip children using ultrasound. J Indian Soc Pedod Prev Dent [serial online] 2012 [cited 2020 Nov 29];30:237-41. Available from: https://www.jisppd.com/text.asp?2012/30/3/237/105017
| Introduction|| |
Nonsyndromic cleft lip (CL) and palate is a complex genetic disorder with variable phenotype, largely attributed to the interactions of the environment and multiple genes, each potentially having certain effects.  A cleft is nonsyndromic if there is only a single malformation, if there are multiple anomalies that are a result of a single initiating event or primary malformation or if multiple anomalies are limited to a single developmental field.  The severity of CL varies considerably from complete bilateral CL and palate at one end of the spectrum to a minimal CL at the other. 
Minimal or microform clefts include superficial scarring or notching of the upper lip, notching of the alveolar ridge (often affecting the adjacent dentition), and asymmetry in the configuration of the alar cartilages. ,, In some cases of microform clefting, there may be no visible manifestation of the defect on the lip surface (i.e., the defect is occult) and no residual functional deficit.  These subepithelial orbicularis oris muscle (OOM) defects are informative subclinical indicators of increased susceptibility to cleft lip/palate (CL/P) because preliminary studies have shown that the OOM is hypoplastic in first degree relatives of CL/P individuals than in controls. 
CL/CP is the fourth most common birth defect. In India, CL/P occurs in nearly 1 in 500 live births.  Reddy et al. reported that in India alone the number of infants born every year with CL/P is 28,600, which means 78 affected infants are born every day or 3 infants with clefts born every hour.  Only a few studies have been conducted to identify subclinically affected individuals within the CL/P families using high resolution ultrasound and no such study has been done in India. The purpose of this study is to use ultrasound to detect defects of the OOM in otherwise clinically normal individuals and to compare the incidence of sub-epithelial orbicularis oris (OO) defects detected by ultrasonography in noncleft first degree relatives of children with CL/P and untreated controls.
| Materials and Methods|| |
Thirty relatives of 25 children with nonsyndromic CL or CL+ CP who reported to the Department of Pedodontics, SGT Dental College, Gurgaon, were identified for the study. Thirty control subjects having negative family history of CL/P in three generations and absence of any minimal cleft features were also selected. Informed consent was taken from all the participants (30 relatives and 30 controls) of the study. Ultrasound scan of all the controls and relatives was taken using linear 14 MHz probe of Acuson Siemens S 2000 manufactured by Siemens ultrasound machine at Medanta, Gurgaon.
The transducer was first positioned on the subject's upper lip, perpendicular to the nasal septum and midway between the columella and vermillion border. Following the natural curvature of the upper lip, the transducer was then moved slowly from the midline to the left, back to the midline, to the right, and back again to midline and scanned. Each scan was recorded on videotape and hardcopy prints of the left and right sides of the lip were made. Only the random number assigned to the subject was recorded on the photographs and videotapes. A single ultrasonographer performed all ultrasound studies, and results regarding OO were not recorded at this time. After all the samples had been scanned, three reviewers independently analyzed each photograph and scored positive or negative. A muscle was considered normal or negative if a continuous hypoechogenic (dark) band of uniform thickness could be visualized, with no obvious discontinuity. Discontinuities manifest in the ultrasound as localized echogenic (bright) areas within the otherwise hypoechogenic muscle tissue, indicating paucity or even complete absence of muscle and these were scored positive. Muscle with isolated areas of thinning, but no clear discontinuity, were considered normal. 
After rating the OOM images independently, the three raters discussed their ratings to reach a consensus. If a consensus could not be reached, the photograph was rated blindly by a fourth rater, and the image was assigned the majority rating. Statistical analysis was performed using standard χ2 tests with Yates correction.
| Results|| |
Lip ultrasounds were performed on 60 non cleft individuals including adults and children who could stay still for the procedure. Among the 30 controls, no OOM defect could be seen [Table 1]. Among the 30 relatives, defects were seen in 4 relatives (13.3%), whereas no defects were present in the rest 26 (86.7%) [Table 1]. Here P = 0.112, that is, P > 0.05, thus proportion of OOM defects was not statistically significantly increased in relatives as compared with controls.
|Table 1: Showing scoring of OOM defects (+ is defect present and – is defect absent)|
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In the sample of 30 relatives, 22 (73.3%) were males and 8 (26.7%) were females, whereas in control group out of 30 individuals 14 (46.7%) were males and 16 (53.3%) were females. Among relatives, defects were seen in 1 (3.3%) male and 3 (10%) females. Among controls, no defect was seen in either males or females. There was a significant increased incidence of defects seen in female relatives over male (3 versus 1, P < 0.05).
| Discussion|| |
Lip/jaw/palatal clefts result in anatomically functional and fine structural alterations of the OOM, while the rest of the facial musculature remains unchanged.  The OOM consists of numerous differently oriented strata of muscular fibers that surround the orifice of the mouth.  The complete OOM architecture forms by 16 weeks. , Any delay in fusion may result in sub-epithelial OOM defects, such as altered migration of the mesenchymal cells. , A CL results from ectodermal breakdown in areas of underlying mesodermal deficiency. , There is evidence that subclinical forms of mesodermal deficiency do occur.  Sub-epithelial (nonvisible) defects of OOM represent the mildest form of CL. , Such morphologies may result from an initial mesenchymal deficiency during primary palatogenesis.  Such defects are part of the phenotypic spectrum of CL/P. , It has been suggested that several of the genes responsible for the CL/P also lead to muscle defects, and highlight the potential importance of including subclinical markers in gene mapping studies of CL/P. 
The excellent sonographic visualization of the mimetic musculature indicates that this technique may be a valuable adjunct in the clinical diagnosis of pathological alterations especially with facial palsy.  Ultrasound imaging of the upper lip is currently one of the most promising methods for identifying subclinical CL/P cases.  High resolution ultrasound method is both noninvasive and cost efficient, both large scale screening of CP families and routine evaluation in a clinical setting are feasible.  Moreover, abnormalities of the OOM visualized by ultrasound have an anatomic basis as revealed through histology. ,
Ultrasound produces an unfamiliar cross sectional image, and structures may have poorly defined boundaries making measurement difficult. For this reason, a detailed knowledge of the anatomy along the plane of section and experience in identifying structures on an ultrasound scan are essential.  In addition, probe should be held perpendicular to the skin as inclination of the transducer is important to obtain a consistent image of skeletal muscle. 
If many genes contribute to a genetic component, each with a small effect, there will be a phenotypic correlation between first degree relatives approaching 0.5 if the environmental contribution to the variation is small, while it will be one-quarter for second degree relatives.  Decline in risk of CL/P to second or third degree relatives was noted by Mitchell and Risch.  Thus it was decided to include only first degree relatives of CL or palate children for the study.
Excessive thinning observed on the ultrasound can be due to displacement resulting from pressure exerted on the pliable soft tissue of the lip by the transducer. This pressure can be particularly problematic when a subject's muscle tissue is initially thin.  Although special care is taken to avoid excess deformation of the lip tissue when obtaining ultrasound data, some deformation is unavoidable.  Thus raters were instructed to pay special attention to the amount of deformation applied by the transducer to avoid false positives. A positive score was given only when a clear and persistent discontinuity (echogenic area) was present within the muscle on the ultrasound.
In this study, out of 30 first degree relatives, OOM defects were seen in 4 relatives, that is, 13.3% of cases, which is in agreement with the findings of Neiswanger et al. (10.3%), although Martins et al. reported the incidence to be 45%. The difference in the results could be attributed to the fact that in this study, positive score was given only when a clear and persistent discontinuity was seen while any thinning of muscle seen was scored negative. We called ultrasound images affected only if a clear discontinuity in the OOM was agreed upon by at least three raters. In the Neiswanger  study, both first degree and more distant relatives were included, whereas only first degree relatives were studied in Martins  and in this study. For rating, ultrasounds still images were used in this study and in the Martins'  study, whereas entire video-sequence was recorded in the Neiswanger  study. Video-sequence allows the rater to discriminate random artifact from an actual OO defect more clearly and may result in fewer images being rated as defects.  This could be one of the limitations of this study. In another study by Weinberg et al., , scores from extended unaffected relatives were compared with those from 52 previously published controls and OOM defects were seen in 44% of the relatives of CL/P probands. In case of controls, no defect of OOM could be seen in this study, although Martin et al. reported the incidence to be 19% in controls, whereas Neiswanger  reported 5.8% incidence. Weinberg et al., reported 11% incidence in controls. Further reason for differences in results could be due to the smaller sample size of relatives and controls in this study.
Higher incidence of OOM defects was seen in female relatives as compared with male relatives. This in not in agreement with reported higher incidence of clefts in males worldwide. , Further study with a bigger sample size might be needed to verify this [Figure 1] and [Figure 2 ].
|Figure 1: Ultrasound image taken in axial plane rated by all reviewers as normal|
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|Figure 2: Representative sample of ultrasound image rated by all reviewers as abnormal or positive defect. Arrow points to echogenic area interrupting hypoechaogenic muscle|
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| Conclusions|| |
Since sub-epithelial OOM defects are relatively straightforward to identify via ultrasound and it is feasible to screen noncleft relatives of an OO defect by ultrasonography in a clinical setting, ultrasound can be an important tool to screen families of CL/P children for subclinical OO defects, and thus provide accurate recurrence risk estimates to relatives. It can be used to further our research in gene studies for CL/P incidence.
The study further supports the hypothesis that subclinical CL cases with subepithelial OOM defects do exist and OO discontinuities represent the mildest form of CL.
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[Figure 1], [Figure 2 ]
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