Enlarged Parietal Foramina

Excerpt

Clinical characteristics: Enlarged parietal foramina are characteristic symmetric, paired radiolucencies of the parietal bones, located close to the intersection of the sagittal and lambdoid sutures, caused by deficient ossification around the parietal notch. Enlarged parietal foramina are usually asymptomatic. Meningeal, cortical, and vascular malformations of the posterior fossa occasionally accompany the bone defects and may predispose to epilepsy. In a minority of individuals, headaches, vomiting, or intense local pain are sometimes associated with the defects, especially on application of mild pressure to the unprotected cerebral cortex.

Diagnosis/testing: The diagnosis of enlarged parietal foramina is established in a proband with characteristic clinical and imaging findings and a heterozygous pathogenic variant in ALX4 or MSX2 identified by molecular genetic testing.

Management: Treatment of manifestations: Treatment is generally conservative. Persistent cranium bifidum may warrant operative closure. The risk for penetrating injury to the brain is small but may cause anxiety; education of parents, teachers, and the affected child to avoid risky behaviors that could result in injury suffices in most circumstances. Treatment of seizures per neurologist; symptomatic treatment of headaches.

Surveillance: Assess osseous defect every six to 12 months until natural history is established; assess for seizures, headache, or other concerning clinical manifestations if symptomatic.

Agents/circumstances to avoid: Contact sports in those with a persistent midline bony defect.

Genetic counseling: Enlarged parietal foramina are inherited in an autosomal dominant manner. Most individuals diagnosed with enlarged parietal foramina have an affected parent. The proportion of individuals with enlarged parietal foramina caused by a de novo pathogenic variant appears to be small. Each child of an individual with enlarged parietal foramina has a 50% chance of inheriting the pathogenic variant. Detailed fetal ultrasound examination at 18 to 20 weeks' gestation can usually detect the defects in a fetus at risk; fetal MRI is also an option. If the pathogenic variant has been identified in an affected family member, prenatal and preimplantation genetic testing are possible.