Congenital high airway obstruction syndrome: MR/US findings, effect on management, and outcome

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Abstract
Background Congenital high airway obstruction syndrome (CHAOS) is a rare disorder defined as any fetal abnormality that obstructs the larynx or trachea. Prompt airway intervention at delivery after accurate prenatal diagnosis may allow survival of this otherwise fatal condition. Objective To identify prenatal MRI findings in CHAOS, to compare these findings with those of fetal US, to determine if imaging alters diagnosis and management decisions, and to correlate prenatal with postnatal imaging findings. Materials and methods Records and MRI scans of ten fetuses with CHAOS were reviewed, and the findings correlated with outside and same-day fetal US and postnatal imaging findings. Fetal lung volumes were measured on MRI scans. Results Large lung volumes were found in 90% of the fetuses. Increased lung signal intensity, inverted diaphragm, and a dilated, fluid-filled lower airway were identified in all. The obstruction level was identified in 90%. MRI changed screening US diagnosis in 70%, but was concordant with the tertiary care US imaging in 90%. Seven fetuses were terminated or died in utero, and three fetuses survived after ex utero intrapartum tracheostomy placement. Autopsy or bronchoscopy performed in 60% confirmed CHAOS. Postnatal chest radiographs and CT showed hyperinflation, while US and fluoroscopy showed diminished diaphragmatic motion. Conclusion MRI demonstrates large lung volumes, increased lung signal intensity, inverted diaphragm, and dilated fluid-filled lower airway, and usually identifies the obstruction level. The degree of correlation between MRI and tertiary prenatal US is high, but CHAOS is frequently misdiagnosed on screening US. Correct diagnosis may enable planned airway management. Voluminous lungs and diaphragmatic abnormalities persist on postnatal imaging.

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