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The fetal larynx and pharynx: structure and development described by 2D and 3D ultrasound examination.
MedLine Citation:
PMID:  23239522     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Objectives: We aimed to present a systemic approach for evaluating the fetal pharynx and larynx based on 2DUS and 3DUS modalities. The sonographic appearance and function of the fetal upper respiratory tract are described; anatomical components of the pharynx and larynx were measured. Methods: Gravidae presenting for booked examinations with singleton fetuses of confirmed gestational age were enrolled. Transabdominal 2DUS was performed for anatomical and functional evaluation. Color Doppler was used to show fluid motion in the target area. 3DUS (Voluson® E6 with RAB-4-8-D transducer) scans of the fetal neck were acquired during fetal quiescence and in the absence of movements of the pharynx and larynx. Multiplanar reconstruction (MPR) in post-processing allowed adjustment of the volume to obtain the coronal plane. After a learning curve to understand the sono-anatomy of the target area, the pharynx width and height, upper, middle, and lower larynx width, and larynx height were measured. Render mode was applied for spatial evaluation of the target area. We developed a new methodological approach for structured evaluation of the fetal pharynx and larynx based on 5 spatial planes: posterior and anterior coronal planes, and high, mid and low axial planes. Results: 582 fetuses were examined during the second trimester of pregnancy; target anatomy was imaged successfully in 218 patients at 11-24 gestational weeks. Acquisition added 1 minute to exam time. Rates of successful visualization and measurements increased significantly as pregnancy progressed, from 23% at 11-13 wks (46/194), 29% at 14-16 (69/240), 35% at 17-19 (18/51), to 88% at 20-24 wks (85/97) (P<0.01). Pharynx components identified were: the sphenoid bone, pterygoid processes, constrictor muscles, the piriform recesses and the uvula. Larynx components defined were: the epiglottis, aryepiglottic folds, corniculate cartilages, arytenoid cartilages, cricoid cartilage, thyroid cartilage and the vocal cords. MPR showed the biconcave shape of the uvula, which may explain the "equal sign" observed in 2DUS. We defined the bilateral mode of movements of the constrictor muscles, aryepiglottic folds, and vocal cords, and the bidirectional fluid jet flows through the larynx. Scatterplots of measured structures versus gestational age were created. Pharynx width ranged from 0.11cm-0.93cm (mean 0.48 ± 0.17); pharynx height ranged from 0.23-2.01cm (mean 0.94 ± 0.33); upper larynx width ranged from 0.04-0.37cm (0.15 ± 0.07); middle larynx width ranged from 0.08-0.77cm (mean 0.34 ± 0.16); lower larynx width ranged from 0.05-0.64cm (0.24 ± 0.11); and larynx height ranged from 0.2-1.83cm (0.71 ± 0.31). All measurements were positively correlated with gestational age. Conclusions: The fetal larynx and pharynx can be thoroughly evaluated using 2DUS and 3DUS modalities. Knowledge of normal anatomy, function and biometry may prove useful in the evaluation of anatomical or functional pathologies involving the fetal upper respiratory tract. Recognition of anatomic anomalies may enhance fetal interventions such as balloon emplacement for cases of diaphragmatic hernia. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.
Authors:
Gad Liberty; Raphael Boldes; Ori Shen; Chanan Shaul; Sarah M Cohen; Simcha Yagel
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-12-13
Journal Detail:
Title:  Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology     Volume:  -     ISSN:  1469-0705     ISO Abbreviation:  Ultrasound Obstet Gynecol     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-12-14     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9108340     Medline TA:  Ultrasound Obstet Gynecol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.
Affiliation:
Department of Obstetrics and Gynecology, Barzilai Medical Center, Ashkelon, Israel. liberg2@gmail.com.
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