Craniovertebral junction anomalies

Last updated: September 21, 2022

Summarytoggle arrow icon

The craniovertebral junction (CVJ) is composed of the occiput, the foramen magnum, and the first two cervical vertebrae, encompassing the medulla oblongata and the upper cervical spinal cord. Anomalies of the CVJ may be congenital or acquired. CVJ anomalies that decrease the volume of the posterior cranial fossa (e.g., platybasia) cause Chiari malformations, while erosion of the cervical vertebrae causes basilar invagination (cranial migration of the odontoid process), and anomalous fusion of the cervical vertebrae causes Klippel-Feil syndrome. Clinical features of CVJ anomalies are due to compression of the brain stem and the spinal cord and may include recurrent occipital headaches, neck aches, bulbar palsy, and upper and lower motor neuron palsy. CVJ anomalies can also obstruct the flow of CSF, resulting in syringomyelia and/or hydrocephalus. Diagnostics include neck x-ray and CT/MRI of the head and neck. Surgery is often indicated to prevent or treat neurological symptoms.

Overviewtoggle arrow icon

Basic anatomy



Chiari malformationstoggle arrow icon

Clinical features and diagnostics of Chiari malformations

Type I CM (Chiari I malformation)

Type II CM (Arnold-Chiari malformation)

Type III CM (Chiari III malformation)

Clinical features
CT/MRI of the brain
  • Treatment
    • Surgery: indicated in all patients with type II and III CM and in symptomatic type I CM
    • Surveillance


Basilar invaginationtoggle arrow icon


Klippel-Feil syndrome (congenital synostosis of the cervical vertebrae)toggle arrow icon


Referencestoggle arrow icon

  1. Chiari Malformations. Updated: January 1, 2014. Accessed: April 10, 2017.
  2. Williams H. A unifying hypothesis for hydrocephalus, Chiari malformation, syringomyelia, anencephaly and spina bifida.. Cerebrospinal Fluid Res. 2008; 5: p.7.doi: 10.1186/1743-8454-5-7 . | Open in Read by QxMD
  3. Chiari Malformation Fact Sheet. Updated: March 13, 2020. Accessed: March 25, 2021.
  4. Klippel-Feil Syndrome. Updated: January 1, 2016. Accessed: April 10, 2017.
  5. Atlanto-axial Impaction (Basilar Invagination). Updated: April 11, 2012. Accessed: April 10, 2017.
  6. Joaquim AF, Ghizoni E, Giacomini LA, Tedeschi H, Patel AA. Basilar invagination: Surgical results. J Craniovertebr Junction Spine. 2014; 5 (2): p.78-84.doi: 10.4103/0974-8237.139202 . | Open in Read by QxMD
  7. Smith JS, Shaffrey CI, Abel MF, Menezes AH. Basilar invagination. Neurosurgery. 2010; 66 (3 Suppl): p.39-47.doi: 10.1227/01.NEU.0000365770.10690.6F . | Open in Read by QxMD
  8. Chamberlain Line on Radiographic Image. Updated: June 1, 2015. Accessed: April 10, 2017.
  9. Lumenta CB, Di Rocco C, Haase J, Mooij JJA. Neurosurgery. Springer ; 2009

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