Normal anatomical variants of cervical spine are not common findings.
Also in most cases asymtomatic and seen incidently during post trauma imaging.
In questionable scenario especially post trauma,
normal variants may be easily misinterpreted as pathology if their knowledge is deficient.
There are number of normal ossification patterns in children,
especially including axis and atlas bones often mimicking pseudotrauma which review is not included.
Also presentation of all normal variants in adults would exceed capacity of this exhibit,
therefore we depicted the most common which are clearly demostrated and described on attached images.
Common C spine normal variants include:
Cervical ribs ( Fig 1.)
Cervical transitional vertebrae occur in approximately 0.5% population,
in over 60% bilaterally.
More common in females.
May give neurological or vascular deficiency symptoms in some cases.
Arcuate foramen ( Fig 2.)
Arcuate foramen is calcification of the oblique atlanto-occipital ligament.
It occurs in around 8% of population and transmits vertebral artery and sub occipital nerve.
More common in females.
Nuchal bones ( Fig 3.)
Nuchal bone is sesamoid ossicle of the nuchal ligament commonly occurring at the level of C5/6 or C6/7.
Incidence: around 8 %.
More common in male.
Asymptomatic in majority of cases.
Occipitalisation of atlas (C1) ( Fig 4.)
Rare condition characterized by fusion of the atlas to the base of the occiput.
May present with headaches,
neck stiffness or dizziness.
Os terminale ( Fig 5.)
It is formed due to failure to fusion of secondary ossification center of dens which occurs between 3-6 years and normally fuses by 12 years.
Dens is usually normal in height.
Os odontoineum ( Fig 6.)
Os odontoineum is a failure of the primary center of ossification of the dens fusion with the body of C2.
(also described by some sources as consequence of childhood trauma)
Congenital cervical spine vertebrae fusion ( Fig 7.)
Congenital C - spine vertebral fusion most frequently involves C2-C3 and then the C3-C4,
however any level may be affected.
Fusion of 2 to 3 segments is common and usually shows no clinical signs of abnormality,
however patient may become symptomatic due to degenerative changes at the site or following trauma.
Prominent vascular channels ( Fig 12.)
Less commonly seen C spine normal variants include:
Solitary lucency through transvese process or double transverse processes
( Fig 9 and 8.)
Non union of secondary ossification centres within spinous processes
( Fig 10.
) or transverse processes.
Cervical vertebrae limbus ( Fig 11.)
Commonly triangular in shape and occupy antero - superior vertebral corner,
however anteroinferior and posterinferior corners may be also affected.
Lumbar spine is most common location.
It is only occasionally seen in cervical spine and therefore may be easily misinterpreted as acute fracture.