A 24 year old non-diabetic, non-alcoholic primigravida with normal obstetric examination came for fetal sonography. A single live fetus was seen with cephalic presentation. Liquor was adequate with closed internal os. Movements were sluggish and scanty. Femur length, abdominal circumference and head circumference all were matching with menstrually calculated gestational age of about 26 weeks. Ultrasound showed well formed cerebral hemispheres with lateral ventricles but without the echogenic rim of skull.
No other obvious internal anomaly was detectable. Fetal echocardiogram showed normal cardiac chambers. Fetal umbilical vessels showed normal flow on doppler.
A diagnosis of acrania was made and the fetus was immediately evacuated by vaginal route using prostaglandins. It was a female fetus with stillbirth. Skull vault and scalp was completely absent with pia covered brain tissue exposed to the exterior.
Acrania ( syn. exencephaly)is a developmental anomaly characterized by complete or partial absence of the neurocranium with complete but abnormal development of brain tissue. This rare lethal anomaly has important implications for obstetrical management and counseling. Prenatal ultrasound readily allows early diagnosis of this condition by the alert sonologist.