Cranio-Vertebral Junction Triangular Area: Quantification of Brain Stem Compression by Magnetic Resonance Images

Abstract

(1) Background: Most of the currently used radiological criteria for craniovertebral junction (CVJ) were developed prior to the popularity of magnetic resonance images (MRIs). This study aimed to evaluate the efficacy of a novel triangular area (TA) calculated on MRIs for pathologies at the CVJ. (2) Methods: A total of 702 consecutive patients were enrolled, grouped into three: (a) Those with pathologies at the CVJ (n = 129); (b) those with underlying rheumatoid arthritis (RA) but no CVJ abnormalities (n = 279); and (3) normal (control; n = 294). TA was defined on T2-weighted MRIs by three points: The lowest point of the clivus, the posterior-inferior point of C2, and the most dorsal indentation point at the ventral brain stem. Receiver operating characteristic (ROC) analysis was used to correlate the prognostic value of the TA with myelopathy. Pre- and post-operative TA values were compared for validation. (c) Results: The CVJ-pathology group had the largest mean TA (1.58 ± 0.47 cm2), compared to the RA and control groups (0.96 ± 0.31 and 1.05 ± 0.26, respectively). The ROC analysis calculated the cutoff-point for myelopathy as 1.36 cm2 with the area under the curve at 0.93. Of the 81 surgical patients, the TA was reduced (1.21 ± 0.37 cm2) at two-years post-operation compared to that at pre-operation (1.67 ± 0.51 cm2). Moreover, intra-operative complete reduction of the abnormalities could further decrease the TA to 1.03 ± 0.39 cm2. (4) Conclusions: The TA, a valid measurement to quantify compression at the CVJ and evaluate the efficacy of surgery, averaged 1.05 cm2 in normal patients, and 1.36 cm2 could be a cutoff-point for myelopathy and of clinical significance.

Nature or nurture: a latent ossification of the posterior longitudinal ligament after atlantoaxial fusion. Illustrative case

“…It was reported that the C1-2 angle was significantly enlarged while the C2-7 angle was reduced significantly after the posterior atlantoaxial fusion surgery for patients of os odontoideum. [7][8][9][10] This evidence supports the prediction that the subaxial alignment parameters will also change in response to the correction of the C1-2 angle. In the present case, we noted the range of motion at the C3-4 level between neck flexion and extension increased from 4 degrees preoperatively to 9 degrees postoperatively.…”

Measurement of Deformity at the Craniovertebral Junction: Correlation of Triangular Area and Myelopathy

“…Our previous study demonstrated that a TA value greater than 1.36 cm 2 was highly associated with myelopathy. 18 The combined conclusions of both studies suggested that anterior odontoidectomy should be highly considered for those patients who had a TA value greater than 2.5 cm 2 . Once the TA value was larger than 2.5 cm 2 , it was less likely to have a TA smaller than 1.36 cm 2 via the posterior approach only, either with decompression or not.…”

“…It has been well reported by many researchers that the retro-odontoid mass tissue disappeared after fixation of the CVJ. 14,17,18,25 Chang et al 17 observed that the TA decreased immediately after the surgery and continued to decrease until 2 years after surgery. In this study, the ΔTA was 1.18 cm 2 in patients who had combined anterior and posterior decompression surgery.…”

“…The TA was defined by 3 points: the lowest point of the clivus, the posterior-inferior point of the C-2 vertebral body, and the most dorsal indentation point in the ventral aspect of the brain stem. For the surgical cases, the pre- and postoperative 2-year TA was measured and compared [ 17 , 18 ].…”

“…The application of TA was further expanded to patients with CVJ trauma and rheumatoid arthritis. Chang et al [ 18 ] reported that patient with a TA value greater than 1.36 cm 2 had high possibility to develop myelopathy that early surgical intervention was highly recommended.…”