Herniation of intracranial structures through skull defect.
Several proposed mechanisms.
Primary failure of cranial neuropore closure.
Secondary event with pressure erosion and herniation of neural tissue.
Failure of induction of membranous bone formation.
Diagnosis and sonographic findings
In the first trimester, we must do endovaginal examination to see the cranial defect.
In the second or third trimester we can see: herniation of mixed cystic and solid mass, normal intracranial landmarks distorted, ventriculomegaly, neuronal migrational anomalies, spina bifida and others anomalies.
The osseous defect is usually midline in the occipital bone.
Scalp masses, cystic hygroma, amniotic band syndrome.
Meckel-Gruber syndrome, Walker-Warburg syndrome, Knobloch syndrome.
Varies with amount of brain tissue in defect and associated malformations.
Referral to neurosurgery prior to delivery for surgical planning. Cesarean section considered to reduce birth trauma.
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Kojima K et al : antenatal evaluation of an encephalocele in imaging. Fetal Diagn Ther.18(5) :338-41,2003
Bannister CM et al : Can prognostic indicators be identified in a fetus with an encephalocele ? Eur J Pediatr Surg 10 Suppl. 1 :20-3,2000