QUIZ: No. 5, 08/02/2026

 CT

Diagnosis: Giant Parietal Foramina

MRI brain with MR venography – To R/O Cortical and venous anomalies

Findings: CT brain (bone window) demonstrates bilateral, symmetric, large oval calvarial defects involving the posterior parietal bones, located parasagittally adjacent to the sagittal suture, with smooth, well-corticated margins and no associated fracture lines, surrounding sclerosis, or destructive bony changes. CT brain (brain window) shows normal underlying brain parenchyma with no evidence of herniation or extra-axial collection. 3D CT clearly delineates the paired parietal calvarial defects.

Discussion

Ø  Congenital calvarial defect due to failure of intramembranous ossification from delayed or incomplete closure of the parietal foramina.

Ø  Commonly associated with ALX4 and MSX2 gene mutations, usually inherited in an autosomal dominant pattern.

Ø  Patients with enlarged parietal foramina (>5 mm) have a higher association with cortical malformations and venous anomalies.

Ø  Next line of investigation: MRI brain with MR venography to evaluate underlying brain parenchyma and venous anatomy.

Ø  Management: No treatment required in asymptomatic patients; rarely, surgical protection may be considered if defects are very large and symptomatic.

Teaching pearl: Bilateral, symmetric parasagittal parietal calvarial defects with smooth corticated margins and no associated soft-tissue component on CT are diagnostic of giant parietal foramina.