Prenatal MRI Findings of Fetuses with Congenital High Airway Obstruction Sequence

Abstract

ObjectiveTo define the MRI findings of congenital high airway obstruction sequence (CHAOS) in a series of fetuses.Materials and MethodsPrenatal fetal MR images were reviewed in seven fetuses with CHAOS at 21 to 27 weeks of gestation. The MRI findings were reviewed. The MRI parameters evaluated included the appearance of the lungs and diaphragm, presence or absence of hydrops, amount of amniotic fluid, airway appearance, predicted level of airway obstruction, and any additional findings or suspected genetic syndromes.ResultsAll the fetuses viewed (7 of 7) demonstrated the following MRI findings: dilated airway below the level of obstruction, increased lung signal, markedly increased lung volumes with flattened or inverted hemidiaphragms, massive ascites, centrally positioned and compressed heart, as well as placentomegaly. Other frequent findings were anasarca (6 of 7) and polyhydramnios (3 of 7). MRI identified the level of obstruction as laryngeal in five cases and tracheal in two cases. In four of the patients, surgery or autopsy confirmed the MRI predicted level of obstruction. Associated abnormalities were found in 4 of 7 (genetic syndromes in 2). Postnatal radiography (n = 3) showed markedly hyperinflated lungs with inverted or flattened hemidiaphragms, strandy perihilar opacities, pneumothoraces and tracheotomy. Two fetuses were terminated and one fetus demised in utero. Four fetuses were delivered via ex utero intrapartum treatment procedure.ConclusionMRI shows a consistent pattern of abnormalities in fetuses with CHAOS, accurately identifies the level of airway obstruction, and helps differentiate from other lung abnormalities such as bilateral congenital pulmonary airway malformation by demonstrating an abnormally dilated airway distal to the obstruction.

Long-term outcomes after fetal therapy for congenital high airway obstructive syndrome

“…This severity may explain why none of our cases had an identified pharyngotracheal or laryngotracheal fistula, although such fistulas have been reported in other series [2,6,12]. Despite the presence of hydrops, survival was still possible in 4 of the 6 patients who did not choose to terminate.…”

“…Fetal MRI may help in choosing patients whose lesions may be amenable to fetoscopic tracheoplasty by determining the level and approximating the length of the lesion [11]. In 1 series, fetal MRI identified the level of obstruction as the larynx vs the trachea in 7 patients, 4 of which were confirmed postnatally [12]. In our most recent patient (case 12), the decision not to offer fetoscopy was based on the MRI findings of a 7-mm laryngeal atresia that did not appear amenable to wire tracheoplasty.…”

A case report of congenital high airway obstruction syndrome (CHAOS) caused by complete laryngeal obstruction

“…4 Though sonography is the main diagnostic tool, MRI can help to better localize the level of obstruction. 5,6 As a natural conclusion of the pathological process, bilateral large hyperechoic lungs, small, compressed, and centrally replaced heart, flattened or inverted diaphragm, and ascites are characteristic findings on sonographic examination. 7 Regarding the amniotic fluid index, compression of the esophagus by dilated airways may lead to polyhydramnios, as the fetal swallowing of the fluid is disrupted.…”

Congenital Chest Malformations: A Multimodality Approach with Emphasis on Fetal MR Imaging

“…CHAOS is a rare abnormality with a poor prognosis and is caused by complete or near-complete obstruction of the fetal airway (16,17), leading to the trapping of lung fluids, hyperplasia of pulmonary alveoli, and tracheal dilatation (9). Fetuses with CHAOS may develop hydrops due to cardiac compression and obstructed venous return (7).…”