MRI of the transverse and alar ligaments in rheumatoid arthritis: feasibility and relations to atlantoaxial subluxation and disease activity

Magnetic resonance imaging anatomy of the craniovertebral ligaments: A radiological study with confirmatory dissection

Background

Descriptions of the radiological appearance of the craniovertebral ligaments often lack detail. This study aimed to provide an accurate description of the morphology and radiological appearance of the alar and cruciform ligaments with confirmation of findings by fine dissection.

Materials and Methods:

Six embalmed human cadaveric specimens were reduced to an osseoligamentous arrangement spanning the C2/3 disc to the occiput. Specimens were imaged on a 4.6T Bruker magnetic resonance (MR) system using a 3D RARE multiple SE sequence with acquisition time 18 h 24 min. Acquired images were viewed in three planes, and detailed descriptions and morphometric measurement of the ligaments were obtained. Specimens were then examined and described using fine dissection. Direct comparison of the descriptions of each method was undertaken.

Results:

From imaging, detailed features of all alar ligaments could be identified in all specimens. Consistency in shape, orientation, and attachments is described. Attachment to the medial aspect of the atlantooccipital joints was evident in all specimens. Five of six alar ligament pairs contained fibers that traversed the dens without attachment. Ascending cruciform ligaments could be clearly identified in four of six specimens. No descending cruciform ligaments could be clearly delineated. Detailed features of the transverse ligaments could be identified and described in all planes. Dissection findings were mostly consistent with descriptions obtained from MR images.

Conclusion:

4.6T MR images provide accurate detail of the structure, dimensions, and attachments of the craniovertebral ligaments. The morphology of the craniovertebral ligaments assessed radiologically was consistent with findings on gross dissection.

Thinking beyond pannus: a review of retro-odontoid pseudotumor due to rheumatoid and non-rheumatoid etiologies

Retro-odontoid pseudotumor, or mass-like retro-odontoid soft tissue thickening, is an uncommon but important imaging finding that may be associated with rheumatoid arthritis, crystal deposition diseases, as well as non-inflammatory conditions such as cervical degenerative changes and mechanical alterations. Retro-odontoid pseudotumor is commonly associated with atlantoaxial microinstability or subluxation. MRI and CT have an important role in the detection and diagnosis of retro-odontoid pseudotumor. However, due to a wide range of imaging characteristics and ambiguous etiology, it is a frequently misunderstood entity. The purpose of this article is to review relevant anatomy of the craniocervical junction; describe various imaging appearances, pathophysiology and histology in both rheumatoid and non-rheumatoid etiologies; and discuss differential diagnosis of retro-odontoid pseudotumor in order to help guide clinical management.

Evaluation of Soft Tissue Hypertrophy at the Retro-Odontoid Space in Patients with Chiari Malformation Type I on Magnetic Resonance Imaging

INTRODUCTION

Chiari malformation type I (CM-I) is a well-known hindbrain disorder in which the cerebellar tonsils protrude through the foramen magnum. The soft tissues, including the transverse ligament and the tectorial membrane at the retro-odontoid space, can compress the cervicomedullary junction if they become hypertrophic.

METHODS

Twenty-two symptomatic patients with CM-I (aged 5-19 years) were treated between 2007 and 2017 at our institute. The retro-odontoid soft tissue was evaluated using T2-weighted magnetic resonance imaging. Anteroposterior (AP) distances and craniocaudal distances of the soft tissue were measured in patients with CM-I and 48 normal control children. Modified clivoaxial angles were also evaluated as the index of ventral compression of the cervicomedullary junction.

RESULTS

Of the 18 patients treated with foramen magnum decompression, 16 patients improved postoperatively, whereas the condition of 2 remained unchanged. The AP distances in the CM-I group (6.0 mm) were significantly larger than those in the control group (3.5 mm), whereas there were no apparent differences in the craniocaudal distances. Modified clivoaxial angles were obviously smaller in the CM-I group (131.5°) than in the control group (146.9°). Moreover, the AP distances were significantly reduced postoperatively (5.5 mm), although the other parameters did not change significantly.

CONCLUSIONS

The retro-odontoid soft tissue in symptomatic patients with CM-I can be hypertrophic enough to compress the cervicomedullary junction ventrally even if there are no combined osseous anomalies. Foramen magnum decompression works to reduce the hypertrophic changes significantly, suggesting that downward tonsil movement might participate in hypertrophic soft tissue formation at the retro-odontoid space.

Are two readers more reliable than one? A study of upper neck ligament scoring on magnetic resonance images

Background

Magnetic resonance imaging (MRI) studies typically employ either a single expert or multiple readers in collaboration to evaluate (read) the image results. However, no study has examined whether evaluations from multiple readers provide more reliable results than a single reader. We examined whether consistency in image interpretation by a single expert might be equal to the consistency of combined readings, defined as independent interpretations by two readers, where cases of disagreement were reconciled by consensus.

Methods

One expert neuroradiologist and one trained radiology resident independently evaluated 102 MRIs of the upper neck. The signal intensities of the alar and transverse ligaments were scored 0, 1, 2, or 3. Disagreements were resolved by consensus. They repeated the grading process after 3–8 months (second evaluation). We used kappa statistics and intraclass correlation coefficients (ICCs) to assess agreement between the initial and second evaluations for each radiologist and for combined determinations. Disagreements on score prevalence were evaluated with McNemar’s test.

Results

Higher consistency between the initial and second evaluations was obtained with the combined readings than with individual readings for signal intensity scores of ligaments on both the right and left sides of the spine. The weighted kappa ranges were 0.65-0.71 vs. 0.48-0.62 for combined vs. individual scoring, respectively. The combined scores also showed better agreement between evaluations than individual scores for the presence of grade 2–3 signal intensities on any side in a given subject (unweighted kappa 0.69-0.74 vs. 0.52-0.63, respectively). Disagreement between the initial and second evaluations on the prevalence of grades 2–3 was less marked for combined scores than for individual scores (P ≥ 0.039 vs. P ≤ 0.004, respectively). ICCs indicated a more reliable sum score per patient for combined scores (0.74) and both readers’ average scores (0.78) than for individual scores (0.55-0.69).

Conclusions

This study was the first to provide empirical support for the principle that an additional reader can improve the reproducibility of MRI interpretations compared to one expert alone. Furthermore, even a moderately experienced second reader improved the reliability compared to a single expert reader. The implications of this for clinical work require further study.

Ligaments of the craniocervical junction

The specialized ligaments of the craniocervical junction must allow for stability yet functional movement. Because injury to these important structures usually results in death or morbidity, the neurosurgeon should possess a thorough understanding of the anatomy and function of these ligaments. To the authors' knowledge, a comprehensive review of these structures is not available in the medical literature. The aim of the current study was to distill the available literature on each of these structures into one offering.

Classification of odontoid destruction in patients with rheumatoid arthritis using reconstructed computed tomography: reference to vertical migration

OBJECTIVE

To reveal the factors that determine the natural course of subluxation of occipital-cervical lesions in rheumatoid arthritis (RA). The atlanto-axial region is one of the most common locations for lesions in RA. Some cases progress from reducible atlanto-axial subluxation (AAS) to irreducible vertical migration, while others continue to exhibit reducible AAS. No study has revealed the factors that determine the natural course of subluxation. We focus on the odontoid as a key structure of the progression of occipito-cervical lesions and investigated this region in patients with RA using reconstructive computed tomography (CT) images, and analyzed factors in association with CT findings.

METHODS

Fifty-eight patients with RA and 40 age-matched controls, all women, were studied. Associated factors, including C-reactive protein, erythrocyte sedimentation rate, steroid usage, and the severity of local osteoporosis, were analyzed as measurements in association with odontoid destruction.

RESULTS

The destruction of odontoid and atlanto-odontoid joint were common in patients with RA. The more destruction observed in the odontoid process, the greater is the degree of progression of vertical migration. Local osteoporosis is a significant factor in odontoid destruction, based on a cortico-cancellous index of 42% in cases of grade III odontoid destruction.

CONCLUSION

The odontoid process is a key structure in the progression of occipito-cervical lesions in patients with RA.