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Cervical Congenital Anomalies

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Other Names

  • Pediatric cervical spine anomalies


  • This page refers to congenital abnormalities of the cervical spine
    • Often associated with pediatric multi-organ system anomalies
    • Some may go undetected
  • The most common, Klippel Feil Syndrome is covered seperately


  • True incidence likely underreported due to undetected cases
  • Estimated that 5% of fetuses have vertebral anomalies[1]
  • Prevalence of congenital fusions of subaxial cervical vertebrae is estimated to be 0.71% on the basis of the study of skeletal specimens[2]
  • Although they can occur at any level, 75% occur in the first 3 cervical vertebrae


Occipital Condyles

  • Rare congenital changes of the condyles of the Occiput
  • Condylus Occipitalis: rare, 3rd condyle sometimes present at midline, benign condition
    • Also called Condylus Tertius
  • Abnormally enlarged condyles: "coconut condyles"

Occipitalization of the atlas

  • Characterized by fusion of the occiput to atlas[3]
    • Occurs in up to 0.25% of the population
  • Associated with: achondroplasia, spondyloepiphyseal dysplasia, Larsen syndrome, and Morquio syndrome
  • Associated with other congenital cervical spine abnormalities
  • Associated with Atlantoaxial Instability, Atlantooccipital Instability
  • These patients may be symptomatic due to weakened or absent travserse atlantal ligament
  • Symptoms include weakness, numbness, pain in upper extremities with associated upper motor neuron exam findings
  • Exam: Short neck, restricted movement, low hairline
  • Treatment is variable
    • C1 may require resection
    • Associated conditions require intervention
    • If cord compression, fusion and stabilization may be required

C1 Anomalies

  • Down syndrome children may have absence of superior articular surface of C1 or fused with C2
  • Anterior or posterior rings may be absence or with defect which can migrate laterally as the child grows
    • This can lead to pain, deformity, basilar invagination, myelopathy
  • Congenital partial aplasia of the posterior arch of the atlas
    • Well described phenomenon in which bony posterior arch is replaced with dense, fibrous band[4]
  • Hypoplasia of the posterior arch
    • Posterior arch is abnormally small, causing canal stenosis and can lead to myelopathy
  • Posticus ponticus: anomalous ossification of the posterolateral surface of the atlas
    • Also termed Ponticulus posticus
    • Leads to encirclement of the vertebral artery which is usually only clinically important in surgical planning


  • Genetic disorder resulting in 'dwarfism'
  • Congenitally, they have a narrowed foramen magnum with upper cervical stenosis
  • May require subocciital decompression, duraplasty to accomodate brain stem and spinal cord growth

Basilar Invagination

  • Characterized or defined by enchroachment of foramen magnum by the upper cervical spine, usually the odontoid process
  • Associated with other congenital abnormalities including atlanto-occipital fusion, hypoplasia of the atlas, hemirings of C1 with ‘‘spreading’’ of the lateral

masses, odontoid abnormalities, KFS, achondroplasia, chiari malformation

  • May also be acquired secondary to other bone disorders including Paget’s disease of bone; osteogenesis imperfecta; Hurler syndrome; and severe rheumatoid arthritis or osteoarthritis
  • Children present with short neck, limited range of motion
    • Symptoms may not present till 2nd or 3rd decade of life
    • May also have muscle weakness, neck pain, posterior column dysfunction, paresthesias[5]
    • Signs include torticollis, limited neck mobility, low hairline, webbed, short neck
  • Treatment
    • Traction: reduce compression of neural structures
    • Posterior occipitocervical stabilization to maintain reduction
    • Alternatively, transoral decompression and occipitocervical fusion


  • Neural tube defect Characterized by
    • Defect to the occipital bone,
    • spina bifida of the cervical vertebrae and
    • Fixed retroflexion (backward bending) or hyperextension of the head on the cervical spine
    • Severe cervical lordosis
  • Treatment
    • Suboccipital release followed by gradual flexion with a halo brace and eventually occipitocervical fusion to maintain correction[6]

Posterior C2 Arch Anomalies

  • Uncommon, but hard to distinguish from tramatic injuries such as spondylolisthesis, Hangman's Fracture
  • May cause myelopathy

Anomalies of the Odontoid

  • Range of pathology from hypoplasia to complete aplasia
  • Associated with Down syndrome, Morquio syndrome, and a variety of other skeletal dysplasias
  • Os Odontoidium: dissociation between C2 body and dens
  • Ossiculum terminale persistens: tip of the dens, the ossiculum terminale, fails to fuse with the remainder of the dens
  • These patients are at high risk of Atlantoaxial Instability and subsequent neurologic injury
  • Present with pain, headache, less commonly myelopathy or quadriparesis from minor trauma
  • Treatment involves posterior stabilization
    • Asymptomatic cases found incidentally are controversial but may require surgical fixation

Cervical Rib

  • See: Cervical Rib
    • Failure of resorption of ossified C7 costal element
    • Can result in variably elongated TP or complete rib


  • Primary motion at Occiput-C1 joint is flexion and extension
    • Represents about 40-50% of total flexion or extension of the neck
  • Primary motion at C1-C2 is rotation
    • Represents 40-50% of total cervical spine motion
  • There are no intervertebral discs at occpital-atlanto or atlanto-axial joints

Risk Factors

  • Fetal Alcohol Syndrome
  • Achondroplasia

Differential Diagnosis

Clinical Features

  • General: Physical Exam Neck
  • History
    • Highly variable
    • Typically report pain, loss of range of motion
    • May endorse neurological symptoms
  • Physical Exam
    • Highly variable
    • Loss of range of motion, stiffness common
    • Torticollis
    • Observe for low hairline, webbed, short neck
    • Thorough neurological exam


  • Basilar Invagination Diagnostic criteria
    • Chamberlain line: drawn between the opisthion to the posterior aspect of the hard palate
    • McRae line: drawn from the anterior to the posterior rim of the foramen magnum
    • McGregor line: drawn from the posterior aspect of the hard palate to the base of the foramen magnum



  • Imaging modality of choice


  • N/A

Rehab and Return to Play


  • Needs to be updated

Return to Play

  • At discretion of surgeon


See Also


  1. Raimondi AJ, Choux M, Di Rocco C. The pediatric spine. New York: Springer-Verlag; 1989
  2. Brown MW, Templeton AW, Hodges FJ 3rd. The incidence of acquired and congenital fusions in the cervical spine. Am J Roentgenol Radium Ther Nucl Med 1964;92:1255–9.
  3. McRae DL, Barnum AS. Occipitalization of the atlas. Am J Roentgenol Radium Ther Nucl Med 1953;70(1):23–46.
  4. Klimo P Jr, Blumenthal DT, Couldwell WT. Congenital partial aplasia of the posterior arch of the atlas causing myelopathy: case report and review of the literature. Spine 2003;28(12):E224–8.
  5. Goel A, Bhatjiwale M, Desai K. Basilar invagination: a study based on 190 surgically treated patients. J Neurosurg 1998;88(6):962–8.
  6. Sherk HH, Shut L, Chung S. Iniencephalic deformity of the cervical spine with Klippel-Feil anomalies and congenital elevation of the scapula; report of three cases. J Bone Joint Surg Am 1974;56(6): 1254–9
Created by:
John Kiel on 17 June 2019 14:30:56
Last edited:
6 October 2022 23:11:24