Prevalence of wormian bones in dried adult human skulls: an osteo-morphometric study in Nepal

The purpose of this study was to determine the incidence of wormian bones (WBs) in different head shapes of Nepalese skulls along with their distribution at various sites. This study was conducted on 70 Nepalese skulls obtained from the Department of Anatomy, Nepal Medical College, and the Institute of Medicine from September 2017 to January 2018. The skulls were examined for the presence and topographic distribution of WBs. The occurrence of WBs at various sites was correlated among different head shapes. The incidence of skulls showing WBs was 88.57%. The WBs were observed at the lambdoid (61.43%), parietomastoid (41.43%), occipitomastoid (27.14%), pterion (25.71%), asterion (24.29%), lambda (11.43%), sagittal (7.14%) and coronal sutures (4.28%). The dominant head type was dolichocephalic (44.29%) and the least dominant was brachycephalic (10%). The maximum number of WBs was shown on brachycephalic (mean 8.86 ± 7.13) then hyperdolichocephalic (mean 8.33 ± 9.15), mesaticephalic (mean 5.10 ± 4.45) and dolichocephalic heads (mean 4.16 ± 5.30). Brachycephalic heads frequently exhibited WBs at the pterion (57.14%) and at different sutures: lambdoid (71.42%), parietomastoid (57.14%), sagittal (28.57%) and squamous (14.28%). Hyperdolichocephalic heads displayed more lambda (33.33%) and coronal (8.33%) WBs. Similarly, dolichocephalic and mesaticephalic heads showed WBs at the occipitomastoid (35.48%) and asterion (30%), respectively. Inca bones were only identified in three dolichocephalic skulls. Neurosurgeons, radiologists and orthopedists should be careful when doing clinical and surgical procedures on different head shapes of the Nepalese population.