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Absent mandibular gap in the retronasal triangle view: a clue to the diagnosis of micrognathia in the first trimester.
Ultrasound Obstet Gynecol. 2012 Feb; 39(2):152-6.UO

Abstract

OBJECTIVE

To describe a new ultrasound technique that may be useful for the diagnosis of micrognathia in the first trimester of pregnancy.

METHODS

The retronasal triangle (RNT) view is a technique that captures the coronal plane of the face in which the primary palate and the frontal processes of the maxilla are visualized simultaneously. Normal first-trimester fetuses display a characteristic gap between the right and left body of the mandible in this view (the 'mandibular gap'). The presence or absence of this gap was evaluated and measured prospectively during real-time scanning (n = 154) and retrospectively by analyzing three-dimensional (3D) datasets (n = 50) in normal first-trimester fetuses undergoing screening for aneuploidy at 11-13 weeks' gestation. 3D datasets from 12 fetuses with suspected micrognathia were also collected and examined retrospectively for the same features.

RESULTS

The mandibular gap was identified in all 204 normal fetuses and increased linearly with increasing crown-rump length (y = 0.033x + 0.435; R(2) = 0.316), with no statistically significant differences between measurements obtained by two-dimensional ultrasound and 3D offline analysis. Among fetuses with suspected micrognathia, three 3D datasets were excluded from analysis because of poor image quality in one and the diagnosis of a normal chin in two. In the remaining nine fetuses, the mandibular gap was absent and was replaced by a bony structure representing the receding chin in seven (77.8%) cases and was not visualized due to severe retrognathia in the remaining two (22.2%) cases. All fetuses with micrognathia had associated anomalies, including seven with aneuploidy and two with skeletal dysplasia.

CONCLUSIONS

The RNT view may be a helpful technique for detecting micrognathia in the first trimester. The absence of the mandibular gap or failure to identify the mandible in this view is highly suggestive of micrognathia and should prompt a targeted ultrasound scan to assess for other anomalies. Further research is needed to determine the false-positive and false-negative rates of this technique.

Authors+Show Affiliations

Fetal Medicine Center, Department of Obstetrics and Gynecology, Clinica Las Condes, Santiago, Chile.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Review

Language

eng

PubMed ID

22009662

Citation

Sepulveda, W, et al. "Absent Mandibular Gap in the Retronasal Triangle View: a Clue to the Diagnosis of Micrognathia in the First Trimester." Ultrasound in Obstetrics & Gynecology : the Official Journal of the International Society of Ultrasound in Obstetrics and Gynecology, vol. 39, no. 2, 2012, pp. 152-6.
Sepulveda W, Wong AE, Viñals F, et al. Absent mandibular gap in the retronasal triangle view: a clue to the diagnosis of micrognathia in the first trimester. Ultrasound Obstet Gynecol. 2012;39(2):152-6.
Sepulveda, W., Wong, A. E., Viñals, F., Andreeva, E., Adzehova, N., & Martinez-Ten, P. (2012). Absent mandibular gap in the retronasal triangle view: a clue to the diagnosis of micrognathia in the first trimester. Ultrasound in Obstetrics & Gynecology : the Official Journal of the International Society of Ultrasound in Obstetrics and Gynecology, 39(2), 152-6. https://doi.org/10.1002/uog.10121
Sepulveda W, et al. Absent Mandibular Gap in the Retronasal Triangle View: a Clue to the Diagnosis of Micrognathia in the First Trimester. Ultrasound Obstet Gynecol. 2012;39(2):152-6. PubMed PMID: 22009662.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Absent mandibular gap in the retronasal triangle view: a clue to the diagnosis of micrognathia in the first trimester. AU - Sepulveda,W, AU - Wong,A E, AU - Viñals,F, AU - Andreeva,E, AU - Adzehova,N, AU - Martinez-Ten,P, Y1 - 2012/01/09/ PY - 2011/10/05/accepted PY - 2011/10/20/entrez PY - 2011/10/20/pubmed PY - 2012/5/1/medline SP - 152 EP - 6 JF - Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology JO - Ultrasound Obstet Gynecol VL - 39 IS - 2 N2 - OBJECTIVE: To describe a new ultrasound technique that may be useful for the diagnosis of micrognathia in the first trimester of pregnancy. METHODS: The retronasal triangle (RNT) view is a technique that captures the coronal plane of the face in which the primary palate and the frontal processes of the maxilla are visualized simultaneously. Normal first-trimester fetuses display a characteristic gap between the right and left body of the mandible in this view (the 'mandibular gap'). The presence or absence of this gap was evaluated and measured prospectively during real-time scanning (n = 154) and retrospectively by analyzing three-dimensional (3D) datasets (n = 50) in normal first-trimester fetuses undergoing screening for aneuploidy at 11-13 weeks' gestation. 3D datasets from 12 fetuses with suspected micrognathia were also collected and examined retrospectively for the same features. RESULTS: The mandibular gap was identified in all 204 normal fetuses and increased linearly with increasing crown-rump length (y = 0.033x + 0.435; R(2) = 0.316), with no statistically significant differences between measurements obtained by two-dimensional ultrasound and 3D offline analysis. Among fetuses with suspected micrognathia, three 3D datasets were excluded from analysis because of poor image quality in one and the diagnosis of a normal chin in two. In the remaining nine fetuses, the mandibular gap was absent and was replaced by a bony structure representing the receding chin in seven (77.8%) cases and was not visualized due to severe retrognathia in the remaining two (22.2%) cases. All fetuses with micrognathia had associated anomalies, including seven with aneuploidy and two with skeletal dysplasia. CONCLUSIONS: The RNT view may be a helpful technique for detecting micrognathia in the first trimester. The absence of the mandibular gap or failure to identify the mandible in this view is highly suggestive of micrognathia and should prompt a targeted ultrasound scan to assess for other anomalies. Further research is needed to determine the false-positive and false-negative rates of this technique. SN - 1469-0705 UR - https://www.unboundmedicine.com/medline/citation/22009662/Absent_mandibular_gap_in_the_retronasal_triangle_view:_a_clue_to_the_diagnosis_of_micrognathia_in_the_first_trimester_ DB - PRIME DP - Unbound Medicine ER -