Atlanto-occipital assimilation

Changed by Yahya Baba, 9 Apr 2023

Disclosures - updated 8 Apr 2023: Nothing to disclose

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Atlanto-occipital assimilation is the fusion of the atlas (C1) to the occiput and is one of the transitional vertebrae.

Epidemiology

Atlanto-occipital assimilation occurs in approximately 0.5% (range 0.08-3%) of the population ^2-5,. It is thought to affect males and females equally.

Clinical presentation

It is typically asymptomatic but symptoms from nerve or vascular compression can occur.

Gross anatomy

Fusion of C1 to the occiput can be either ³:

complete: C1 not identifiable
incomplete: C1 partially identifiable

It can also be classified as

posterior arch assimilation
anterior arch assimilation
assimilation of both the anterior and posterior arches

Associations

Atlanto-occipital assimilation is associated with ²:

fusion of C2 and C3 (occurs in 50% of cases)
basilar invagination: type 1
cleft palate
cervical ribs
urinary tract anomalies
cranio-cervical instability ⁵

-<p><strong>Atlanto-occipital assimilation</strong> is the fusion of the <a href="/articles/atlas-c1">atlas</a> (C1) to the occiput and is one of the <a href="/articles/transitional-vertebra">transitional vertebrae</a>. </p><h4>Epidemiology</h4><p>Atlanto-occipital assimilation occurs in approximately 0.5% (range 0.08-3%) of the population <sup>2-5,</sup>. It is thought to affect males and females equally.</p><h4>Clinical presentation</h4><p>It is typically asymptomatic but symptoms from nerve or vascular compression can occur. </p><h4>Gross anatomy</h4><p>Fusion of C1 to the occiput can be either <sup>3</sup>:</p><ul>
+<p><strong>Atlanto-occipital assimilation</strong> is the fusion of the <a href="/articles/atlas-c1">atlas</a> (C1) to the occiput and is one of the <a href="/articles/transitional-vertebra">transitional vertebrae</a>. </p><h4>Epidemiology</h4><p>Atlanto-occipital assimilation occurs in approximately 0.5% (range 0.08-3%) of the population <sup>2-5</sup>, It is thought to affect males and females equally.</p><h4>Clinical presentation</h4><p>It is typically asymptomatic but symptoms from nerve or vascular compression can occur. </p><h4>Gross anatomy</h4><p>Fusion of C1 to the occiput can be either <sup>3</sup>:</p><ul>

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Case 6

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