Enlarged parietal foramina

Enlarged parietal foramina is an inherited condition of impaired skull development. It is characterized by enlarged openings (foramina) in the two bones (parietal bones) that form the top and sides of the skull. This condition is due to problems with bone formation (ossification) within the parietal bones. The openings are symmetrical and circular in shape, with variable size ranging from a few millimeters to several centimeters wide. Parietal foramina are a normal feature of fetal development, but they usually close by the fifth month of pregnancy.

The area covering the parietal foramina is soft to the touch. Pressure applied to the openings can lead to severe headaches. People with enlarged parietal foramina usually do not have any related medical problems; however, scalp defects, seizures, and structural brain abnormalities have been noted in a small percentage of affected people. The risk of brain damage may be increased if any trauma is experienced in the area of the openings.

The incidence of enlarged parietal foramina is estimated to be between 1 in 15,000 and 25,000 individuals.

Mutations in the ALX4 and MSX2 genes cause enlarged parietal foramina.

The MSX2 and ALX4 genes provide instructions for producing proteins called transcription factors, which are required for proper development throughout the body. Transcription factors attach (bind) to specific regions of DNA and help control the activity of particular genes.

Mutations in either MSX2 or ALX4 can disrupt a number of necessary cell functions. The cells involved in skull development seem to be particularly sensitive to these disruptions.

If the condition is caused by a mutation in the MSX2 gene it is called enlarged parietal foramina type 1. A mutation in the ALX4 gene causes enlarged parietal foramina type 2. There appears to be no difference in the size of the openings between enlarged parietal foramina types 1 and 2.

Read more about the ALX4 and MSX2 genes.

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

In most cases, an affected person has one parent with the condition. A small number of cases may result from new mutations in the gene. These cases occur in people with no history of the disorder in their family.