{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T17:24:08Z","timestamp":1784568248330,"version":"3.55.0"},"reference-count":14,"publisher":"Scientific Scholar","content-domain":{"domain":["surgicalneurologyint.com"],"crossmark-restriction":true},"short-container-title":[],"abstract":"<jats:sec id=\"st1\">\n<jats:title>Background: <\/jats:title>\n<jats:p>Atlas occipital assimilation (AOA) is a rare developmental anomaly of the craniocervical junction, with a poorly understood natural history. Therefore, in 15 cases, we reassess the clinical profile of three types of AOA.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"st2\">\n<jats:title>Methods: <\/jats:title>\n<jats:p>For 15 patients, we applied the 3 classifications: type 1 (4 patients; unilateral joint union (hemi-assimilation), type 2 (7 patients; bilateral joint union with atlas cleft (three-way), and type 3 (4 patients; bilateral joint union and complete union of the posterior arch (circumferential). Variables studied included age, sex, neurological status, pathological magnetic resonance findings, and clivo-axial angles (CAAs).<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"st3\">\n<jats:title>Results: <\/jats:title>\n<jats:p>For these 15 patients, we discovered no significant gender differences. However, type 1 AOA affected younger people, type 2 involved more middle-aged\/elderly people, and type 3 had most elderly population. Interestingly, all 7 type 2 patients were asymptomatic, and symptoms for the remaining patients included cough, headache, upper limb numbness (i.e., due to Chiari type 1 malformation [CM1] in type 1 patients), and myelopathy (i.e., due to spinal canal stenosis at C1-2 in type 3 patients). In addition, 75% of type 3 AOA patients had C2-3 fusions. The average CAA was 127.5\u00b0 for type 1 and 139\u00b0 for types 2 and 3. Decompressive surgery was performed for type 1 and decompression with fusions for type 3 patients.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"st4\">\n<jats:title>Conclusion: <\/jats:title>\n<jats:p>Half of the AOA cases are asymptomatic. However, symptomatic cases require attention to CM1 in young people and atlanto-axial dislocation in elderly people.<\/jats:p>\n<\/jats:sec>","DOI":"10.25259\/sni_701_2025","type":"journal-article","created":{"date-parts":[[2025,9,19]],"date-time":"2025-09-19T06:02:38Z","timestamp":1758261758000},"page":"399","update-policy":"https:\/\/doi.org\/10.25259\/crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Clinical features of atlas occipital assimilation: A retrospective study"],"prefix":"10.25259","volume":"16","author":[{"given":"Hisaaki","family":"Uchikado","sequence":"first","affiliation":[{"name":"Department of Neurosurgery, Uchikado Neuro-Spine Clinic, Fukuoka, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takehiro","family":"Makizono","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, Kurume University School of Medicine, Kurume, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jin","family":"Kikuchi","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, Kurume University School of Medicine, Kurume, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yosuke","family":"Hashimoto","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, Kurume University School of Medicine, Kurume, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takayasu","family":"Ando","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, Kurume University School of Medicine, Kurume, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gohsuke","family":"Hattori","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, Kurume University School of Medicine, Kurume, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Motohiro","family":"Morioka","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, Kurume University School of Medicine, Kurume, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"10894","published-online":{"date-parts":[[2025,9,19]]},"reference":[{"key":"10.25259\/SNI_701_2025\/ref-1","doi-asserted-by":"crossref","first-page":"833","DOI":"10.1007\/s00276-013-1235-9","article-title":"A case of atlas assimilation: Description of bony and soft structures","volume":"36","author":"Ciolkowski","year":"2014","journal-title":"Surg Radiol Anat"},{"key":"10.25259\/SNI_701_2025\/ref-2","doi-asserted-by":"crossref","first-page":"1763","DOI":"10.1097\/BRS.0000000000001045","article-title":"Atlas assimilation patterns in different types of adult craniocervical junction malformations","volume":"40","author":"Ferreira","year":"2015","journal-title":"Spine (Phila Pa 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