Vertex Craniotabes

GENESIS

Prolonged forceful pressure on the presenting part, usually at the vertex affecting the superior portions of the parietal bones, may result in diminished mineralization within the compressed region. The calvarium is generated from the underlying dura mater, and persistent growth-stretch tensile forces restrain cranial ossification and maintain sutural patency. Persistent cranial pressure mimics the mechanical impact of growth-stretch forces and results in temporarily restrained, localized calvarial ossification. Craniotabes is more likely to occur in first born infants, and elicited history often shows that the fetus has experienced early fetal head descent and has been in the vertex position deep within the maternal pelvis for an unusually long period of time. Because this is usually the mother’s first pregnancy, she may not be aware of anything unusual other than symptoms of urinary frequency and pressure. The frequency of reported cases of craniotabes has varied over time, with congenital infection thought to be a common underlying cause in the past. Today, craniotabes can be a fairly common finding and may be found in up to 20–30% of normal neonates. Mild degrees of compression-related craniotabes occur in about 2% of newborns, whereas more extensive degrees of craniotabes are less common.

Since the theory of a compression-related pathogenesis for benign vertex craniotabes was first advanced in 1979, several reports have investigated whether craniotabes might be a useful sign for the detection of subclinical rickets due to vitamin D deficiency. Most studies failed to demonstrate any significant correlations among maternal and infant serum vitamin D, calcium, phosphorus, and alkaline phosphatase levels; craniotabes; and skeletal mineralization. However, one study showed small but statistically significant decreases in serum calcium and phosphate in mothers of infants with craniotabes compared with mothers of infants with a normal calvarium. There has been a number of reports of newborns being born with severe craniotabes owing to insufficient maternal sunlight exposure during the COVID-19 pandemic. Another study showed that the mean serum 25-hydroxyvitamin D level by radio assay was significantly lower in newborns with craniotabes and in their mothers compared with control mother-infant pairs without craniotabes. Two papers each presenting four cases of neonatal rickets were reported in infants with craniotabes who were born to mothers with florid osteomalacia due to vitamin D–deficiency rickets (causing these mothers hip and back pain and an impaired waddling gait). Both the infants and their mothers had low serum concentrations of 25-hydroxyvitamin D, elevated alkaline phosphatase, and borderline or low serum calcium and phosphorous, and they responded to treatment with vitamin D. In one population-based study, nutritional rickets was associated with Black race, breast-feeding, low birth weight, and stunted growth. Four of 13 patients (31%) who underwent 25-hydroxyvitamin D testing had values less than 10 ng/mL. These studies indicate that deficient maternal vitamin D intake can lead to neonatal rickets in which craniotabes may be a presenting feature, and this diagnosis should be considered in any infant without signs of fetal head compression whose mother may be at risk for nutritional deficiency; however in these cases, the infant usually manifests generalized craniotabes and osteomalacia. There have been genetic syndromes such as Noonan syndrome described with craniotabes, but these have all been linked to vitamin D–deficiency rickets.