Porotic hyperostosis (PH) is the expansion of the cranial diploë, generating ‘hair-on-end’ appearance on X-rays. This condition is extremely rare and had a prevalence of 0.08%. It is alternatively known as cribra orbitalia (CO) when the orbital roof is affected. In this study, we describe the gross morphology of two skulls affected by PH and CO. The first skull belonged to a 41-year-old female previously diagnosed with beta thalassemia. The skull was affected by excessive PH and CO. The second skull, belonging to a 35-year-old male diagnosed with unspecified thalassemia, showed PH without CO. The etiology of PH and CO is discussed. In conclusion, PH and CO are extremely rare, and are of significant importance for radiologists and anatomists when interpreting radiographs or encountering unusual gross morphology of the skull.

Porotic hyperostosis (PH) is the expansion of the cranial diploë, generating ‘hair-on-end’ appearance on X-rays. This condition is extremely rare and had a prevalence of 0.08%. It is alternatively known as cribra orbitalia (CO) when the orbital roof is affected. In this study, we describe the gross morphology of two skulls affected by PH and CO. The first skull belonged to a 41-year-old female previously diagnosed with beta thalassemia. The skull was affected by excessive PH and CO. The second skull, belonging to a 35-year-old male diagnosed with unspecified thalassemia, showed PH without CO. The etiology of PH and CO is discussed. In conclusion, PH and CO are extremely rare, and are of significant importance for radiologists and anatomists when interpreting radiographs or encountering unusual gross morphology of the skull.

This study consists of a retrospective cohort study, a systematic review, and a meta-analysis which were separately conducted. This study aimed to investigate the prevalence of atlas arch defects, generate an evidence-based synthesis, and propose a common classification system for the anterior and combined atlas arch defects. Atlas arch defects are well-corticated gaps in the anterior or posterior arch of the atlas. When both arches are involved, it is known as a combined arch defect. Awareness of these defects is essential for avoiding complications during surgical procedures on the upper spine. The prevalence of arch defects was investigated in an open-access OPC-Radiomics (Radiomic Biomarkers in Oropharyngeal Carcinoma) dataset comprising 606 head and neck computed tomography scans from oropharyngeal cancer patients. A systematic review and meta-analysis were performed to generate prevalence estimates of atlas arch defects and propose a classification system for the anterior and combined atlas arch defects. The posterior arch defect was found in 20 patients (3.3%) out of the 606 patients investigated. The anterior arch defect was not observed in any patient, while a combined arch defect was observed in one patient (0.2%). A meta-analysis of 13,539 participants from 14 studies, including the present study, yielded a pooled-posterior arch defect prevalence of 2.07% (95% confidence interval [CI], 1.22%–2.92%). The prevalences of anterior and combined arch defects were 0.00% (95% CI, 0.00%–0.10%) and 0.14% (95% CI, 0.04%–0.25%), respectively. The anterior and combined arch defects were classified into five subtypes based on their morphology and frequency. The present study showed that atlas arch defects were present in approximately 2% of the general population. For future studies, larger sample sizes should be used for studying arch defects to avoid the small-study effect and to predict the prevalence accurately.