Teaching NeuroImages: Enlarged parietal foramina inadvertently labeled as burr holes

A 49-year-old woman presented with status migrainosus. A CT head revealed only bilateral symmetric burr holes in the posterior paramedian calvarium despite no prior cranial surgery (figure). These holes ultimately represented enlarged parietal foramina (EPF) unrelated to her presentation. EPF are rare developmental defects of the parietal bones (prevalence of 1:15,000–50,000) commonly due to an abnormal ossification pattern associated with heterogeneous homeobox gene mutations. Though rarely associated with craniofacial and vascular malformations, headaches, and epilepsy, EPF are usually benign, incidental findings, ranging from few millimeters to several centimeters in diameter, and frequently located in the upper, posterior parietal bones.1,2