Atlanto-occipital assimilation
Atlanto-occipital assimilation is the fusion of the atlas (C1) to the occiput and is one of the transitional vertebrae.
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Epidemiology
Atlanto-occipital assimilation occurs in approximately 0.5% (range 0.25-1%) of the population 2-4.
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
Associations
Atlanto-occipital assimilation is associated with 2:
- fusion of C2 and C3 (occurs in 50% of cases)
- basilar invagination
- cleft palate
- cervical ribs
- urinary tract anomalies
Related Radiopaedia articles
Anatomy: Spine
-
osteology
- vertebrae
- spinal canal
- cervical spine
- thoracic spine
- lumbar spine
- sacrum
- coccyx
-
anatomical variants
- vertebral body
- neural arch
- transitional vertebrae
- ossicles
- ossification centres
- intervertebral disc
- articulations
- ligaments
- musculature of the vertebral column
- muscles of the neck
- muscles of the back
-
suboccipital muscle group
- rectus capitis posterior major muscle
- rectus capitis posterior minor muscle
- obliquus capitis superior muscle
- obliquus capitis inferior muscle
- splenius capitis muscle
- splenius cervicis muscle
- erector spinae group
- transversospinalis group
- quadratus lumborum
-
suboccipital muscle group
-
spinal cord
- gross anatomy
-
white matter tracts (white matter)
- anterolateral columns
- lateral columns
-
dorsal columns
- fasiculus gracilis (column of Goll)
- fasiculus cuneatus (column of Burdach)
- grey matter
- nerve root
- spinal meninges and spaces
- functional anatomy
- spinal cord blood supply
- sympathetic chain
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