Congenital high airways obstruction syndrome

A congenital high airways obstruction syndrome (CHAOS) refers a rare often lethal congenital laryngo-tracheal condition and is primarily characterised by a distal obstruction to airways and fetal lungs distally.

Pathology

A CHAOS can be of 3 possible types ²

• complete laryngeal atresia without an oesophageal fistula
• complete laryngeal atresia with a tracheo-oesophageal fistula
• near-complete high upper airway obstruction 

Associations

• Fraser syndrome

Radiographic features

Antenatal ultrasound

Ultrasound may show some of all of the following features 

• dilated trachea / bronchi : distal to the obstruction ^4-5
• enlarged and echogenic lungs ^4-5
• diaphragmatic inversion and / or flattening ^4-5 
• presence of fetal ascites ^4-5
• the fetal heart may appear displaced to the midline and compressed

Ancillary sonographic features include

• presence of fetal anasarca ⁷
• presence of polyhydramnios ⁵

Fetal MRI

May confirm features detected on ultrasound as well as more accurately show the level of obstruction. Lung signal increased ⁵. 

Treatment and prognosis

The prenatal natural history and postnatal course of CHAOS often depends on whether the airway obstruction is complete. An ex utero intrapartum treatment (EXIT) procedure may offer potential for salvage ^1,3. Overall prognosis is considered considered generally poor ⁶.

See also

• tracheal atresia