From the Guidelines
Scalloping of the skull vault in a fetus is primarily caused by increased intracranial pressure, which leads to thinning and remodeling of the inner table of the skull, as a result of conditions such as hydrocephalus, intracranial tumors, or certain congenital malformations, as reported in recent studies 1. The most common causes of scalloping include hydrocephalus (excessive cerebrospinal fluid accumulation), intracranial tumors, or certain congenital malformations.
- In some cases, scalloping may be associated with genetic syndromes such as osteogenesis imperfecta, craniosynostosis, or skeletal dysplasias.
- The pressure causes the inner surface of the skull to develop indentations that follow the gyral pattern of the brain. This phenomenon occurs because fetal skull bones are more malleable than adult bones, allowing them to be shaped by internal pressures. When identified on prenatal ultrasound or MRI, further evaluation is necessary to determine the underlying cause, as this finding may indicate a serious neurological or developmental condition requiring specialized care after birth, and recent studies have shown that ultrasound is a safe and effective method for detecting congenital anomalies, including scalloping of the skull vault 1. The use of non-invasive prenatal testing (NIPT) and cell-free fetal DNA in the maternal blood has also become a valuable tool in detecting fetal genetic material and identifying potential anomalies, with a detection rate for trisomy 21 of 99% and a false positive rate of 0.5% in women who receive results 1. However, it is essential to note that NIPT cannot replace ultrasound for detection of anomalies, and a comprehensive evaluation is necessary to determine the underlying cause of scalloping and provide appropriate care 1.
From the Research
Causes of Scalloping of Skull Vault in Fetus
- Scalloping of the skull vault in a fetus can be caused by various factors, including:
- Thanatophoric dysplasia type II (TD2), a lethal skeletal dysplasia that can cause hydrocephalus, macrocephaly, and a cloverleaf skull 2
- Amniotic band syndrome, which can cause exencephaly with acrania/acalvaria 3
- Acalvaria, a rare congenital anomaly characterized by the partial or complete absence of the skull vault 3
- The development and growth of the skull vault is a complex process involving the interaction of multiple tissues, including the neural tube, surface ectoderm, and dura mater 4
- Mutations in certain genes can lead to abnormalities of the skull vault, and the study of these genes has revealed complex molecular interactions involved in the formation of the skull vault 4
- Fetal magnetic resonance imaging (MRI) can be used to detect abnormal sulcation patterns, corpus callosal agenesis, and posterior fossa anomalies, which can be associated with scalloping of the skull vault 5
- The diagnosis of thanatophoric dysplasia and other skeletal dysplasias can be made prenatally using ultrasound and MRI, and can be confirmed by molecular testing and autopsy findings 2, 6