Population-level assessment of atlas occipitalization in artificially modified crania from pre-Hispanic Peru

Abstract

Atlas occipitalization (AO) is a spinal anomaly, characterized by the fusion of the first cervical vertebra and occipital bone, with a complex etiology that can arise from congenital and environmental causes. AO has been reported in three regions of pre-Hispanic Peru in skeletal remains with artificial cranial modification (ACM), which involves the use of compression devices to permanently alter cranial shape and may have affected the fusion of the atlas and occipital bone. The aims of this study were to gain insights into AO's etiology by testing correlations between AO and ACM presence/type and geographic region as well as to characterize morphological variation associated with AO. We investigated the geographic distribution of AO and its potential relationship to ACM in a large sample of human crania from eight coastal and highland regions of pre-Hispanic Peru, held at the Smithsonian's National Museum of Natural History (n = 608, 1300-1500 CE). Eleven cases of AO were observed in three coastal regions-including two previously unreported regions-at an overall frequency of 1.8%. The frequency of AO did not differ significantly between crania with and without ACM, in general or by type, suggesting that ACM is not an etiological factor that influences AO in this sample. AO was observed at a significantly higher rate in the southern coastal region of Arequipa than in any other region. Genetic, dietary, and epidemiological conditions are evaluated as factors possibly shaping the geographic distribution of AO along the central and southern coasts of Peru.

Metopic skull with occipitalisation of the atlas

“…AO is normally congenital, but in rare cases it may be a result of diseases such as osteomyelitis, arthritis, syphilis, tuberculosis and other infections or traumatic injuries of the cervical vertebrae [31,36]. Factors such as malnutrition or disease-related disturbances during development or genetic anomalies may also predispose a fetus toward developing AO [31].…”

“…AO is normally congenital, but in rare cases it may be a result of diseases such as osteomyelitis, arthritis, syphilis, tuberculosis and other infections or traumatic injuries of the cervical vertebrae [31,36]. Factors such as malnutrition or disease-related disturbances during development or genetic anomalies may also predispose a fetus toward developing AO [31]. It has been reported that AO could be associated with Pfeiffer, Crouzon and Apert syndromes involving craniosynostosis, as well as with Goldenhar, Klippel-Feil and Pierre-Robin syndromes [5,16].…”

“…Since AO and the related abnormalities could be asymptomatic they often goes undetected and AO is commonly diagnosed incidentally in radiographs, intraoperatively or during autopsy. The reported AO frequency ranges between 0.03 -3.6 % in the contemporary populations [12,16,31].…”

Radiological Features of Atlas Occipitalization and Its Clinical Implications

“…The reported prevalence of occipitalization ranges from 0.08% to 2.76%. [1][2][3][4] Clinically, occipitalization is one of the most common features of congenital atlantoaxial dislocations (AADs), which can cause severe neurological deficits and usually require surgical intervention. 5,6 These symptoms usually do not develop until the fourth or fifth decades of life.…”

“…Occipitalization, or assimilation of the atlas, implies congenital bony union between the occiput and the first cervical vertebra (C1). The reported prevalence of occipitalization ranges from 0.08% to 2.76% 1–4. Clinically, occipitalization is one of the most common features of congenital atlantoaxial dislocations (AADs), which can cause severe neurological deficits and usually require surgical intervention 5,6.…”