Report and review of the fetal brain disruption sequence

The fetal brain disruption sequence (FBDS), a rare cause of extreme microcephaly, is described in a patient and compared with 19 previously reported cases. Clinical findings present in almost all patients included: severe microcephaly (average occipitofrontal circumference -5.8 SD), overlapping sutures, prominent occipital bone, scalp rugae with normal hair patterning and marked neurological impairment. Early death occurred in 7/20 cases. The FBDS was sporadic in 17 out of 19 reported cases supporting a low recurrence risk for genetic counselling purposes. A group of related observations in cases were thromboembolic phenomenon following death of the co-twin, vascular and/or haematological involvement by prenatal cytomegalovirus infection, prenatal cocaine exposure, direct vascular fetal trauma (cordocentesis) and fetal vascular changes after a maternal car accident causing intracranial bleeding and brain damage. Normal scalp hair pattern in all cases and the second or third trimester location of the disruptive event in two cases suggest that in the FBDS, brain growth is normal throughout the first 18 weeks of gestation at least.

Pathogenic factors suggest that different forms of vascular injury to the fetal brain (emboli, haemorrhage, vasoconstriction, disseminated intravascular coagulation) can produce partial brain destruction, diminished intracranial pression and skull collapse in the fetal brain disruption sequence.