Ross Hauser, MD. Reviews of Diagnostic Imaging Technology for Cervical Spine Instability

Ross Hauser, MD.

Reviews of Diagnostic Imaging Technology for Cervical Spine Instability

Humans spend the larger part of each day in the upright position, the very position that causes most symptoms, yet most diagnostic tests are performed with the patient in the supine, resting position, the very position that gives them relief. Scanning in the upright position can show the brain, brainstem, and cervical spine under the effects of gravity, and its alterations in blood flow, venous drainage, and cerebrospinal fluid flow can also be seen while the person is upright. Many times, symptomology occurs with a specific head/neck position such as flexion, so scanning the patient in the symptomatic position and motion will improve diagnostic accuracy.

Unrecognized differences in intervertebral alignment between supine and upright positions

The problem of unrecognized differences in supine and upright positions is seen in a December 2022 paper. Doctors at the University of Pittsburgh (9) writing in the Journal of orthopaedic research discussed the possible post-surgical complications in patients undergoing cervical spine surgery due to unrecognized differences in intervertebral alignment between supine and upright positions.

The study authors write: “Cervical sagittal alignment is a critical component of successful surgical outcomes. Unrecognized differences in intervertebral alignment between supine and upright positions may affect clinical outcomes; however, these differences have not been quantified.” The doctors looked at this problem by following sixty-four patients who had one or two-level cervical arthrodesis for symptomatic pathology from C4-C5 to C6-C7.

In these patients, as well as control patients, the C1-C2, C2-C3, and C3-C4 motion segments were in more lordosis when upright as compared with supine. However, the C4-C5, C5-C6, and C6-C7 motion segments were in less lordosis when upright as compared with supine. Motion changes at C1-C and C2-C3 indicate that cervical motion segment alignment changes between supine and upright positioning, those changes differ among motion segments, and cervical pathology affects the magnitude of these changes.

The authors concluded: “Surgeons should be mindful of the differences in alignment between supine and upright imaging and the implications they may have on clinical outcomes.”

Joint instability is difficult to detect by supine static scanning methods. To find joint instability, especially in the neck, it is important to scan the person when they are upright and preferably during motion or their symptomatic position, whether it be with upright x-rays, MRI, or position CT scans.

In a 2013 paper, doctors writing in the European spine journal (1) described this problem. “(our results) show a high rate of false negative results in cases of hidden discoligamentous (disc and ligament) injuries by using conventional radiographic analysis as well as quantitative motion analysis in plain lateral radiographs in a trauma setting. Despite the technical possibilities in a modern trauma center, our data and recent literature indicate a thorough clinical and radiographic follow-up of patients with cervical symptoms to avoid secondary complications from missed cervical spine injuries.”

The structural and clinical effects of upper and lower cervical instability and whiplash injury can be readily observed and quantified with advanced imaging technology. These new technologies and the resultant understanding of the biomechanics and neuropathology of cervical instability and whiplash injuries are of critical importance in the treatment of these injuries and in proving their existence in the medical-legal realm. These imaging modalities are readily available. However, analysis of the results is a timely and complex task. These modalities are as follows:

Cervical Digital Motion X-ray (C-DMX)

Cervical Digital Motion X-ray (C-DMX) – This modality is essentially a video-fluoroscopic x-ray movie of the spine in motion. The procedure is completed with a device resembling a conventional C-arm. However, far less radiation is utilized than theoretically would be emitted with a conventional C-arm, due to the use of digital processing technology.

A DMX of the spine allows for a continuous and detailed examination of cervical spinal movement. DMX allows unrestricted assessment of C0-C7 motion in multiple dimensions including sagittal, rotational, and frontal planes. DMX studies typically include moving the head and neck through protraction, retraction, flexion, extension, rotation, and lateral flexion; while observing in real-time, the motion of the cervical vertebrae from C0-C7.

The DMX studies show the functional integrity of the ligaments in the cervical spine, specifically the anterior and posterior longitudinal, supraspinous, interspinous, ligamentum flavum, facet capsular ligaments, transverse, and alar ligaments. Conventional cervical spinal X-rays are static views of the spine as a snapshot in time and, perforce, cannot evaluate the spine in real-life motion. The DMX is a comprehensive movie of the cervical spine in all axes of movement and includes the open-mouth odontoid view in motion, which is the critical view of the C1-C2 vertebral relationship during lateral flexion.

Digital motion x-ray (videofluoroscopic) examination of the cervical spine has been shown to provide a high degree of diagnostic accuracy for the identification of vertebral instability in patients with chronic pain stemming from whiplash trauma. (2) Dynamic MRI in the craniocervical instability (CCJ Instability) was found to be able to detect cases of cord compression that were not seen by static supine MRI. (3) In a study involving 1,200 patients, cerebellar tonsillar descent (Chiari) of at least 1 mm was 4 times more likely to be diagnosed by an upright MRI vs. one supine. (4) Cerebellar tonsillar ectopia was found 2.5 times more often in whiplash patients when an upright MRI was done vs. one that was supine. Soft tissue lesions in this study and others are found in the upper cervical region about 3-5 times more often when an upright (especially with flexion/extension views) vs. recumbent is done.(5,6,7,8)

The digital motion x-ray is explained and demonstrated below.

Digital Motion X-ray shows instability at the C1-C2 Facet Joints
The amount of misalignment or “overhang” between the C1-C2 demonstrates the degree of instability in the upper cervical spine.
At 0:40 of this video, a repeat DMX is shown to demonstrate the correction of this problem.

Critical relationships observed and quantified in the DMX analysis include:

Cervical lordosis versus abnormal straightening of the cervical spine with loss of sagittal spinal balance.

DMX Facet relationships and ligamentous instability, expressed as facet gapping in cervical flexion in oblique and AP spinal views

Facet relationships and ligamentous instability are expressed as facet gapping in cervical flexion in oblique and AP spinal views.
- In the image below the caption reads Digital Motion X-ray cervical spine oblique view showing capsular ligament injuries. In the neutral position, the neuroforamina is open or mostly open at all levels. In extension, they close off to varying degrees at C3 (moderate) C4 (severe), C5 (severe), and C6 (moderate). This is indicative of capsular ligament injury.

Foraminal compression during oblique flexion-extension views

Foraminal compression during oblique flexion-extension views.
- In the image below the caption explains: Digital motion x-rays documenting the closure of several cervical neural foramina. Inbox/image A. Neural foramina C3 – C7 are open in this oblique view of neck extension. Inbox/image B. The neural foramina are still open in this 2nd pass of the neck extension (arrow). C. In this 3rd neck extension, the C4 neural foramen is closed (arrow). D. The neural foramina from C4-C7 are all closed (arrow) in this 4th pass extension.

DMX Anterolisthesis (forward slip) and retrolisthesis (posterior slip) in flexion and extension.

Anterolisthesis (forward slip) and retrolisthesis (posterior slip) in flexion and extension.
- In the image below the caption reads Anterolisthesis of the neck. This digital motion x-ray depicts multi-level anterolisthesis of the C4-C7 vertebrae. This person’s symptoms were increased significantly with work that required neck flexion (long periods in front of the computer for example) which correlated with this scan.

DMX demonstrating C1 lateral flexion and extension sequences

The ring of C1 in strictly lateral flexion and extension sequences should not open or be canted. If the ring does not remain in a strictly perpendicular position, it is unstable.
Atlanto-Dental Interval (ADI) – measured in the lateral view during flexion vs. extension. In an adult, the anterior tubercle of C1 should not extend more than 3 mm in front of the odontoid and if it does, that is an indication of loss of transverse ligament integrity. Partial subluxation in the form of the “V” sign is also abnormal
Lateral Atlanto-Dental Interval (LADI) – measured in concert with the overhang of the lateral masses of C1 and C2 seen in the coronal open-mouth odontoid view, is the distance between the medial wall of the lateral mass of C1 and the lateral wall of the odontoid process. If C1 is balanced correctly in a stable fashion on C2 with lateral flexion of the neck, the left and right LADI will be equal and there will be no measurable overhang of the lateral borders of C1 and C2. On the other hand, if whiplash-induced lateral C1-C2 instability occurs, the lateral overhang in a non-rotated view (verified by equal width measurements of both lateral masses) will exceed 2 mm. In our studies, they can be as high as 10 mm and an average of 4.7 mm in such trauma. The LADI measurements will also change in instability from whiplash. For example, in left lateral flexion, if the overhang measures 6 mm, the left LADI will be larger than the right LADI as the right lateral mass will be shifted towards the odontoid. The relationship is not strictly linear.

In this image, the caption reads Digital Motion X-ray demonstrating severe bilateral atlantoaxial (C1-C2) instability with open mouth view and lateral neck flexion.

Right posterior malrotation of C2

In this image – the caption reads right posterior malrotation of C2. In this open-mouth view, the C2 spinous process is to the right of the midline in comparison to the dens of the C2. These malrotations, when present chronically, are a sign of C1-C2 instability.

Magnetic Resonance Imaging

Cervical Positional Weight Bearing (CpMRI) MRI is a cervical MRI that is done in the upright neutral position, and preferably in the position of maximum flexion and extension. This also can slow instability, as well as some critical anatomy in the C1 and C2 regions.

Magnetic Resonance Imaging (MRI) is based on the principle that atoms and molecules have specific electromagnetic frequency responses when subjected to an oscillating magnetic field. The device consists of a tunnel surrounded by a complex electromagnetic coil and the patient, lying recumbent in the device, also have tight secondary coils about their body. Varying high power oscillating fields are introduced, eliciting specific secondary electromagnetic fields, which complex algorithms convert into images called sequences. In contradistinction to conventional X-rays, on which CT scanning is based, MRI does not “depict” skeletal structures per se, but rather demonstrates soft tissue, such as brain, spinal cord, muscle, ligaments, vertebral discs, bone marrow, and blood vessels. Abnormalities such as spinal cord injury, herniated discs, ligament injury, and structural anomalies and pathology are well visualized with MRI.

Three cross-sections of upper spinal cord MRI.

In this image, the caption explains Three cross-sections of upper spinal cord MRI. In the A Image: Normal MRI. In the B image: Partial blockage of cerebrospinal fluid posteriorly. C image: Complete blockage of cerebrospinal fluid posteriorly.

Magnetic Resonance Angiography (MRA) is based on the same principles as MRI. However, the software extracts the signals focused on flowing blood within blood vessels and then reconstructs a 3-D image of these vessels. MRA is useful in the diagnosis of vertebral artery compression and arterial obstructions such as seen in upper cervical instability or stroke. CT Angiography (CTA) is an invasive alternative to MRA requiring an IV injection of iodinated dye. In both of these tests, it is important to do the angiographic portion of the test with the neck turned in the direction of the suspected vertebral artery compression.

The Circle of Willis, the convergence of several arteries at the bottom of the brain as seen with an MRI angiogram.

Cine MRI and Dynamic MRI are modalities whereby time-gated signals sequentially analyze the pulsations of CSF and blood flow. Synthesized dynamic imaging depicts this data as a “movie.” As regards the craniocervical and C1-C2 injury issues discussed here, the obstructive effect of foramen magnum stenosis on craniocervical CSF flow is well depicted, as is transient obstruction of the vertebral arteries. It is critical for anyone with unresolved headaches to obtain a cervical motion x-ray and MRI scan.

In positional upright weight-bearing MRI, the patient is seated or standing in a specialized MRI scanner. A secondary coil is placed around the target region, such as the cervical spine, and the patient is placed in stressed positions, such as flexion, extension, or lateral flexion. With analogy to the DMX concept, CpMRI is a more “realistic” representation of the target, such as the cervical spine, under physiological conditions. It is not quite “motion,” as the patient must be perfectly still to achieve usable images, but the next option. The pathology that is visualized includes injured alar or transverse ligaments with stress applied to them in lateral flexion, cervicomedullary junctional compression by the mass effect of C1 capsulosynovitis during flexion, and accentuated cervical herniated discs, that are larger and more easily seen during extension.

Traditional radiographic testing, including MRIs, x-rays, and CT scans, is often done in the supine static position and can miss the true diagnosis. When these and other diagnostic tests, such as digital motion x-ray and transcranial, extracranial, and transorbital Doppler ultrasounds, as well as electrocardiograms and heart rate variability examinations, are done while the head and neck are moving and/or in the upright position, not only can cervical instability be visualized and diagnosed, but so can the pathophysiology it is causing. A treatment plan to restore as best as possible the cervical anatomy, lordotic curve, and stability with cervical vertebral adjustments, cervical spine curve correction, and Prolotherapy, respectively, can be done and successful treatment can be verified not just by symptom resolution but also by repeat testing methods documenting improvements.

Please see these articles for related discussions:

We hope you found this article informative and it helped answer many of the questions you may have surrounding imaging for cervical spine problems. Just like you, we want to make sure you are a good fit for our clinic prior to accepting your case. While our mission is to help as many people with chronic pain as we can, sadly, we cannot accept all cases. We have a multi-step process so our team can really get to know you and your case to ensure that it sounds like you are a good fit for the unique testing and treatments that we offer here.

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