= complex developmental anomaly characterized by

1. Exaggerated lordosis
2. Rachischisis
3. Imperfect formation of skull base at foramen magnum

M÷F = 1÷4

Associated with other anomalies in 84%:

anencephaly, encephalocele, hydrocephalus, cyclopia, absence of mandible, cleft lip / palate, diaphragmatic hernia, omphalocele, gastroschisis, single umbilical artery, CHD, polycystic kidney disease, arthrogryposis, clubfoot

• dorsal flexion of head
• abnormally short + deformed spine

Prognosis: almost uniformly fatal

DDx:

1. Anencephaly
2. Klippel-Feil syndrome
3. Cervical myelomeningocele