Combined ossification of the posterior longitudinal ligament at C2-3 and invagination of the posterior axis resulting in myelopathy

Abstract

Purpose: Spinal stenosis at the C2-3 segment is a rare occurrence, and when it occurs myelopathy infrequently results. Furthermore, only a handful of cases involving congenital abnormalities of the posterior arch of the axis have been described resulting in cervical myelopathy many of which described simultaneous congenital abnormalities at adjacent levels and none of which identified ossification of the posterior longitudinal ligament (OPLL) at the same level. We report a case of a previously undescribed combination of abnormalities at the C2-3 segment resulting in clinical myelopathy.

Methods: A 49-year-old Chinese male presented with a progressive cervical myelopathy (C-JOA score 11 immediately pre-op). Segmental OPLL at the C2-3 disk space was visible, together with invagination of the bilaterally hypoplastic C2 lamina into the spinal canal. Signal abnormalities of the spinal cord were evident on both T1 and T2 sequences.

Results: The patient underwent a posterior decompression and instrumented fusion at C2-3 using pars screws at C2 and lateral mass screws at C3. Following surgery there was a rapid and significant improvement in the neurological symptoms, with the C-JOA score improving to 14 at final follow-up. A successful fusion was evident.

Conclusions: Deficiencies in the posterior arch of the axis are rare and have not previously been reported in conjunction with OPLL. Advanced imaging is helpful to define the abnormality and site of compression. In the setting of a progressive neurological dysfunction, surgical decompression and stabilization is a reasonable intervention and can be associated with neurological and symptomatic improvement.

Fig. 1

Pre-operative lateral radiographs in flexion and extension, respectively

Fig. 2

Pre-operative T-2 sagittal MRI right para-sagittal and mid-sagittal, respectively

Fig. 3

Pre-operative sagittal CT scan right para-sagittal and mid-sagittal, respectively

Fig. 4

Axial CT scan at the level of the C2–3 revealing invagination of the C2 Lamina

Fig. 5

Post-operative lateral and AP radiographs at final follow-up

Fig. 6

Post-operative sagittal MRI

Fig. 7

Post-operative axial MRI demonstrating adequate decompression

Fig. 8

a Transverse schematic of the axis approximately 3 months following birth reveals normal development with the two neurocentral synchondrosis anteriorly with squaring off of the dens, and ossification extending posteriorly towards the spinous processes. b Transverse schematic at approximately 5 years reveals complete ossification of the posterior arch (typically complete by 3–4 years) with incomplete fusion to each other (typically complete by 5 years) resulting in a bifid arch. The anterior neurocentral synchondroses with the body are still visible (typically complete by 7 years). Failure of the neurocentral synchondroses to close (spondylolysis) together with failure of the posterior ossification centers to fuse results in floating laminae [1, 3, 8, 9, 17] A complete description of the previously described abnormalities of the posterior axis are described in Table 1. c Embryology of the craniocervical junction. Yellow occipital sclerotomes 1&2, Magenta occipital sclerotome 3, Purple occipital sclerotome 4, Light Green first spinal sclerotome, Dark Green first and second spinal sclerotomes, Brown second spinal sclerotome