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The Craniovertebral Junction (CVJ) is the anatomical region where the base of the skull meets the upper cervical spine—a complex transitional zone that plays a vital role in mobility, stability, and neural protection.
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It includes bones, joints, ligaments, and neurovascular structures.
Drawing showing the embryonic origin of the various bony parts of the craniocervical junction. The “pro-atlas” contributes to the formation of occipital condyles, the lateral masses of the atlas bone and the apex of the odontoid process. The 1st cervical sclerotome (C1) contributes to the formation of the anterior and posterior arcs of the atlas along with the base of the odontoid process. The 2nd cervical sclerotome (C2) contributes to the formation of the body of the atlas.
Aurélien Courvoisier. Congenital Cervical Spinal Deformities. Orthopaedics & Traumatology Surgery & Research. 2022;109(1):103459-103459. doi:https://doi.org/10.1016/j.otsr.2022.103459
Key Anatomy of the CVJ
| Component | Description |
|---|---|
| Occiput | Skull base portion, contains the foramen magnum |
| Atlas (C1) | Ring-shaped vertebra, lacks a body; supports the skull via the atlanto-occipital joints |
| Axis (C2) | Contains the odontoid process (dens) that articulates with the anterior arch of C1 |
| Joints | - Atlanto-occipital (Occiput–C1): flexion-extension- Atlantoaxial (C1–C2): axial rotation |
| Ligaments | Cruciate ligament, alar ligaments, apical ligament, tectorial membrane – all stabilize CVJ |
| Neural structures | Lower medulla, upper cervical spinal cord, CN XI, vertebral arteries pass through |
| Vascular | Vertebral arteries ascend through transverse foramina of C1–C6 and enter the skull via foramen magnum |
Sagittal illustration demonstrating the major craniocervical ligaments, including the tectorial membrane (blue), anterior atlanto-occipital membrane, apical ligament, cruciform ligament (superior and inferior longitudinal bands and transverse bands), and posterior atlanto-occipital membrane and their relationship with surrounding ligaments, skull base, and bony anatomy of the cervical spine
Fiester, Peter; Rao, Dinesh; Soule, Erik; Orallo, Peaches1; Rahmathulla, Gazanfar2. Anatomic, functional, and radiographic review of the ligaments of the craniocervical junction. Journal of Craniovertebral Junction and Spine 12(1):p 4-9, Jan–Mar 2021. | DOI: 10.4103/jcvjs.JCVJS_209_20
Axial illustration demonstrating the deep ligaments of the craniocervical junction, including the tectorial membrane (cut), transverse band of the cruciate ligament, and alar ligaments and their anatomic relationship with the brainstem and vertebral arteries
Fiester, Peter; Rao, Dinesh; Soule, Erik; Orallo, Peaches1; Rahmathulla, Gazanfar2. Anatomic, functional, and radiographic review of the ligaments of the craniocervical junction. Journal of Craniovertebral Junction and Spine 12(1):p 4-9, Jan–Mar 2021. | DOI: 10.4103/jcvjs.JCVJS_209_20
Coronal, anterior illustration demonstrating the ligaments of the craniocervical junction including the tectorial membrane (cut), cruciate ligament, alar ligament, apical ligament, and posterior longitudinal ligament
Fiester, Peter; Rao, Dinesh; Soule, Erik; Orallo, Peaches1; Rahmathulla, Gazanfar2. Anatomic, functional, and radiographic review of the ligaments of the craniocervical junction. Journal of Craniovertebral Junction and Spine 12(1):p 4-9, Jan–Mar 2021. | DOI: 10.4103/jcvjs.JCVJS_209_20
Imaging modalities:
| Modality | Purpose |
|---|---|
| XR | Static: Screening; detects fractures, instability, dens anomalies |
| Dynamic: Assess instability, especially in trauma or RA | |
| CT | Best for bony detail, congenital anomalies, surgical planning |
| MR | Evaluate neural compression, ligamentous injury, associated Chiari malformation, or syringomyelia |
Normal Radiological Parameters of CVJ
| Measurement | Normal Value | Significance |
|---|---|---|
| Atlanto-dental interval (ADI) | <3 mm (adults), <5 mm (children) | Increased = Atlantoaxial instability |
| Chamberlain’s line | Dens tip ≤ 3 mm above | >3 mm = Basilar invagination |
| McGregor’s line | Dens tip ≤ 4.5 mm above | Similar to Chamberlain’s line |
| Wackenheim’s line | Should intersect or be tangent to dens | Displacement = CVJ anomaly |
| Skull base angle | 125°–143° | >143° = Platybasia |
Demonstration of the three main measurements of the craniovertebral junction on a T1-weighted image of a pediatric patient. The distance between the Chamberlain (brown) and the McGregor (green) lines is small. The Welcher-basal angle (yellow) is formed by a line running from the nasion to the tuberculum sella and a second line running from the tuberculum along the posterior margin of the clivus. A Welcher-basal angle larger then 140° indicates platybasia
Pinter, N.K., McVige, J. & Mechtler, L. Basilar Invagination, Basilar Impression, and Platybasia: Clinical and Imaging Aspects. Curr Pain Headache Rep 20, 49 (2016). https://doi.org/10.1007/s11916-016-0580-x
a, b The atlantodens interval (ADI) and the space available for cord (SAC) are used in determining atlantoaxial instability. The ADI increases as the SAC decreases. A SAC less than 13 mm is significant
Ghanem I, El Hage S, Rachkidi R, Kharrat K, Dagher F, Kreichati G. Pediatric cervical spine instability. Journal of Children’s Orthopaedics. 2008;2(2):71-84. doi:10.1007/s11832-008-0092-2
![LEFT: Cross-sectional view of occipitocervical junction (OCJ). The following parameters are often used when interpreting sagittal computed tomography scan or lateral radiograph for signs of pathology at OCJ. Dens should remain below Wackenheim line, which is drawn as tangent to posterior slope of clivus. McRae line connects tip of clivus to opisthion, and protrusion of dens above it is abnormal. Chamberlain and McGregor lines use hard palate as reference point for 2 additional lines, and protrusion of dens 3 mm above Chamberlain line and 4.5 mm above McGregor line is abnormal. Atlantodental interval (ADI; sometimes anterior ADI [AADI]), is usually less than 3 mm in adults and 5 mm in children. At this spinal level, minimum space available for cord (SAC) to avoid compression is 14 mm RIGHT: Midline sagittal computed tomography of normal anatomy. Hard palate is commonly not well visualized on neck CT. Wackenheim clivus baseline (A), posterior axial line or posterior vertebral line (B), and angle that they form, clivus–canal angle (a), are shown. McRae line (C), Chamberlain line (D), and McGregor line (E) are also shown. Lines are drawn to demonstrate Redlund-Johnell criterion. Distance from inferior body of axis (C2) to McGregor line (F) should be less than 29 mm in women or less than 34 mm in men.
Benke M, Yu WD, Peden SC, O'Brien JR. Occipitocervical junction: imaging, pathology, instrumentation. Am J Orthop (Belle Mead NJ). 2011;40(10):E205-E215.](attachment:b8fe9fb1-75ec-4d70-8e0a-39a2cf337760:CVJ_Lines.jpg)
LEFT: Cross-sectional view of occipitocervical junction (OCJ). The following parameters are often used when interpreting sagittal computed tomography scan or lateral radiograph for signs of pathology at OCJ. Dens should remain below Wackenheim line, which is drawn as tangent to posterior slope of clivus. McRae line connects tip of clivus to opisthion, and protrusion of dens above it is abnormal. Chamberlain and McGregor lines use hard palate as reference point for 2 additional lines, and protrusion of dens 3 mm above Chamberlain line and 4.5 mm above McGregor line is abnormal. Atlantodental interval (ADI; sometimes anterior ADI [AADI]), is usually less than 3 mm in adults and 5 mm in children. At this spinal level, minimum space available for cord (SAC) to avoid compression is 14 mm RIGHT: Midline sagittal computed tomography of normal anatomy. Hard palate is commonly not well visualized on neck CT. Wackenheim clivus baseline (A), posterior axial line or posterior vertebral line (B), and angle that they form, clivus–canal angle (a), are shown. McRae line (C), Chamberlain line (D), and McGregor line (E) are also shown. Lines are drawn to demonstrate Redlund-Johnell criterion. Distance from inferior body of axis (C2) to McGregor line (F) should be less than 29 mm in women or less than 34 mm in men.
Benke M, Yu WD, Peden SC, O'Brien JR. Occipitocervical junction: imaging, pathology, instrumentation. Am J Orthop (Belle Mead NJ). 2011;40(10):E205-E215.
