Absent cranial vault

Absent telencephalon and encephalon

Polyhydramnios

Vertebral splaying ± overlying soft tissue

Lemon sign

Banana sign

Reported in trisomy 13 and 18

Additional anomalies in 40%

Arnold-Chiari type II malformation

Ventriculomegaly

Tethered spinal cord

Aneuploidy (4% in isolation, 14% with other anomalies)

Fatal

Severity depends on level of the lesion; worse with higher level defects

With lumbar/sacral: possible bowel, bladder, mobility, and neurologic dysfunction