Premium
Absent mandibular gap in the retronasal triangle view: a clue to the diagnosis of micrognathia in the first trimester
Author(s) -
Sepulveda W.,
Wong A. E.,
Viñals F.,
Andreeva E.,
Adzehova N.,
MartinezTen P.
Publication year - 2012
Publication title -
ultrasound in obstetrics and gynecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.202
H-Index - 141
eISSN - 1469-0705
pISSN - 0960-7692
DOI - 10.1002/uog.10121
Subject(s) - medicine , coronal plane , chin , first trimester , fetus , ultrasound , mandible (arthropod mouthpart) , maxilla , 3d ultrasound , pregnancy , anatomy , orthodontics , radiology , botany , biology , genetics , genus
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. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.