{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T17:23:53Z","timestamp":1784568233597,"version":"3.55.0"},"reference-count":36,"publisher":"Journal of Neurosurgery Publishing Group (JNSPG)","issue":"7","license":[{"start":{"date-parts":[[2026,2,16]],"date-time":"2026-02-16T00:00:00Z","timestamp":1771200000000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J Neurosurg Case Lessons"],"published-print":{"date-parts":[[2026,2,16]]},"abstract":"<jats:sec>\n                    <jats:title>BACKGROUND<\/jats:title>\n                    <jats:p>Atlas assimilation is the most common congenital anomaly of the craniocervical junction and is consistently associated with type I basilar invagination (BI1). Its precise bone composition and distribution, however, remain poorly defined.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>OBSERVATIONS<\/jats:title>\n                    <jats:p>All BI1 patients demonstrated atlas assimilation, which was absent in controls. The condyle-mass complex was the most consistent pattern, forming a continuous monoblock in all cases. Atlas anterior arch\u2013basion fusion was universal but asymmetrical in 2 patients, while posterior arch fusion was complete in 5 patients and partial in 3. Compared with controls, BI1 patients exhibited elongated suboccipital, shortened clivus, shortened exoccipital, and widened lateral masses.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>LESSONS<\/jats:title>\n                    <jats:p>CT with multiplanar and 3D reconstructions provides a comprehensive evaluation of atlanto-occipital assimilation in BI1. The condyle-mass complex was the most consistent assimilation site, while anterior and posterior arch fusions were variable. Atlanto-occipital assimilation in BI1 appears to extend beyond midline structures, involving consistent exoccipital\u2013atlas lateral mass nonsegmentation.<\/jats:p>\n                    <jats:p>\n                      <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"uri\" xlink:href=\"https:\/\/thejns.org\/doi\/10.3171\/CASE25765\">https:\/\/thejns.org\/doi\/10.3171\/CASE25765<\/jats:ext-link>\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.3171\/case25765","type":"journal-article","created":{"date-parts":[[2026,2,23]],"date-time":"2026-02-23T11:47:13Z","timestamp":1771847233000},"source":"Crossref","is-referenced-by-count":1,"title":["Atlanto-occipital assimilation: the role of exoccipital, basioccipital, and suboccipital bones in the physiopathology of type I basilar invagination. Patient series"],"prefix":"10.3171","volume":"11","author":[{"given":"Thiago M. M.","family":"Maciel","sequence":"first","affiliation":[{"name":"Post-graduation Program, Instituto de Assist\u00eancia M\u00e9dica ao Servidor P\u00fablico Estadual de S\u00e3o Paulo\u2013IAMSPE, S\u00e3o Paulo"},{"name":"Department of Neurosurgery, Hospital Municipal de Parelheiros Josanias Castanha Braga, S\u00e3o Paulo, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ricardo V.","family":"Botelho","sequence":"additional","affiliation":[{"name":"Post-graduation Program, Instituto de Assist\u00eancia M\u00e9dica ao Servidor P\u00fablico Estadual de S\u00e3o Paulo\u2013IAMSPE, S\u00e3o Paulo"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1754","reference":[{"issue":"4","key":"bib1","series-title":"Childs Nerv Syst","first-page":"523","article-title":"Embryology and bony malformations of the craniovertebral junction","volume":"27","author":"Pang","year":"2011","unstructured":"Pang DThompson DNP.Embryology and bony malformations of the craniovertebral junction. Childs Nerv Syst. 2011;27(4):523-564. doi:10.1007\/s00381-010-1358-9"},{"issue":"22","key":"bib2","series-title":"Spine (Phila Pa 1976)","first-page":"1763","article-title":"Atlas assimilation patterns in different types of adult craniocervical junction malformations","volume":"40","author":"Ferreira","year":"2015","unstructured":"Ferreira EDZBotelho RV.Atlas assimilation patterns in different types of adult craniocervical junction malformations. Spine (Phila Pa 1976). 2015;40(22):1763-1768. doi:10.1097\/BRS.0000000000001045"},{"key":"bib3","series-title":"World Neurosurg","first-page":"201","article-title":"Role of atlas assimilation in the context of craniocervical junction anomalies","volume":"151","author":"Joaquim","year":"2021","unstructured":"Joaquim AFEvangelista Santos Barcelos ACDaniel JW.Role of atlas assimilation in the context of craniocervical junction anomalies. World Neurosurg. 2021;151:201-208. doi:10.1016\/j.wneu.2021.05.033"},{"issue":"5","key":"bib4","series-title":"Childs Nerv Syst","first-page":"975","article-title":"Atlas assimilation: spectrum of associated radiographic abnormalities, clinical presentation, and management in children below 10 years","volume":"36","author":"Menezes","year":"2020","unstructured":"Menezes AHDlouhy BJ.Atlas assimilation: spectrum of associated radiographic abnormalities, clinical presentation, and management in children below 10 years. Childs Nerv Syst. 2020;36(5):975-985. doi:10.1007\/s00381-019-04488-3"},{"issue":"5","key":"bib5","series-title":"Yale J Biol Med","first-page":"487","article-title":"Basilar impression (platybasia): a bizarre developmental anomaly of the occipital bone and upper cervical spine with striking and misleading neurologic manifestations","volume":"11","author":"Chamberlain","year":"1939","unstructured":"Chamberlain WE.Basilar impression (platybasia): a bizarre developmental anomaly of the occipital bone and upper cervical spine with striking and misleading neurologic manifestations. Yale J Biol Med. 1939;11(5):487-496."},{"key":"bib6","series-title":"World Neurosurg X","first-page":"100418","article-title":"Craniospinal space reduction and malalignment due to atlas assimilation in basilar Invagination\u2014a case-control study","volume":"25","author":"Botelho","year":"2024","unstructured":"Botelho RVPetranchi BCBBotelho PBMoreira DUMBertolini EFRotta JM.Craniospinal space reduction and malalignment due to atlas assimilation in basilar Invagination\u2014a case-control study. World Neurosurg X. 2024;25:100418. doi:10.1016\/j.wnsx.2024.100418"},{"issue":"2","key":"bib7","series-title":"Natl J Med Res","first-page":"238","article-title":"An unusual case of unilateral atlanto-occipital assimilation with skull asymmetry","volume":"2","author":"Rajani","year":"2012","unstructured":"Rajani SJSuttarwala IMRajani JK.An unusual case of unilateral atlanto-occipital assimilation with skull asymmetry. 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