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LETTERS TO EDITOR
Year : 2019  |  Volume : 67  |  Issue : 1  |  Page : 318-321

Absence of axis (C2) posterior elements leading to C2–C3 instability and myelopathy in young adults


1 Department of Neurosurgery and Gamma Knife Center, All India Institute of Medical Sciences, AIIMS, New Delhi, India
2 Department of Anatomy, All India Institute of Medical Sciences, AIIMS, New Delhi, India

Date of Web Publication7-Mar-2019

Correspondence Address:
Dr. Hitesh K Gurjar
Department of Neurosurgery and Gamma Knife Center, All India Institute of Medical Sciences, AIIMS, New Delhi - 110029
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.253646

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How to cite this article:
Meena RK, Gurjar HK, Singh S, Aggarwal D. Absence of axis (C2) posterior elements leading to C2–C3 instability and myelopathy in young adults. Neurol India 2019;67:318-21

How to cite this URL:
Meena RK, Gurjar HK, Singh S, Aggarwal D. Absence of axis (C2) posterior elements leading to C2–C3 instability and myelopathy in young adults. Neurol India [serial online] 2019 [cited 2019 Mar 18];67:318-21. Available from: http://www.neurologyindia.com/text.asp?2019/67/1/318/253646




Sir,

A 25-year old male patient came to our outpatient services with complaints of weakness on the left side of the body, urinary frequency, and urge incontinence for the last 6 months. Weakness was insidious in onset, gradually progressive and not associated with sensory symptoms. There was no history of neck pain or trauma to the neck. General physical examination was normal. There were no cranial nerve deficits. Motor examination showed a normal bulk and reduced power (4/5 Medical Research Council grade ) on the left side of the body with hyper-reflexia and upgoing plantar reflex bilaterally. Sensory examination showed 20% loss to all modalities at C4 and below.

X-ray of the cervical spine [Figure 1]a showed the presence of an occipitalized  Atlas More Details, absent posterior elements of C2 with no articulating facets between C2 and C3. Dynamic X-rays [Figure 1]b of the cervical spine showed significant motion between C2 and C3. Non-contrast cervical spine CT scan [Figure 2] showed the absence of spinous process, lamina, and the inferior articular facet of the axis and pars. The pedicle of C2 was small and rudimentary. Atlas was occipitalized, and C3 spinous process was hypertrophied [Figure 3]. Magnetic resonance imaging [Figure 4] of the cervical spine showed degenerated C2-3 disc, cord compression, and T2 hyperintensity of the cord with focal cord atrophy at C2-3 level.
Figure 1: Preoperative X-ray of the cervical spine. (a) Normal position; (b) Dynamic position showing C2-3 instability (arrow), absence of posterior elements of C2 and hypertrophied spinous process of C3

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Figure 2: CT scan of the cervical spine( a-d) showing sequential sagittal views and, (e) single axial view showing absent lamina,spinous process, pars interarticularis,and inferior articular facet of axis

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Figure 3: Three-dimensional (3D) reconstructed CT scan of the cervical spine with angiography (a-c) delineating the course of bilateral vertebral arteries

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Figure 4: Preoperative MRI imaging of the cervical spine, sagittal view (a and b) showing the absence of posterior elements of C2, degenerated C2-C3 disc and cord compression

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In view of the presence of myelopathy and significant movement at C2-3, it was decided to operate this patient. The patient then underwent an occipitocervical fixation [Figure 5] using the contoured rod and lateral mass screws. At a 3-month follow-up, the patient had neurological improvement and partially regained his urinary continence.
Figure 5: Postoperative X-ray of the cervical spine showing the occipito-cervical fusion with contoured rods and screws

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Developmental anomalies of the upper cervical spine are not uncommon. These developmental anomalies usually affect the atlas or the odontoid process of the axis.[1],[2] However, anomalies involving the posterior elements of the axis are extremely rare.[1],[3],[4] Only 10 case reports exist in the English literature, regarding deficient posterior elements of the axis [Table 1].
Table 1: Reported cases of absent posterior elements of axis in the literature

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In 1987, Morizono et al.,[7] reported the first case of absent spinous process and arch of C2 along with the hypertrophied spinous process of C3 and C2/3 anterolisthesis in a 20-year-old male patient who presented with neck pain and headache after trauma. This patient was managed conservatively with spinal traction. Behari et al.,[5] reported another two cases of absent posterior elements of C2 associated with atlantoaxial dislocation (AAD). Similarly, Srivastava et al.,[2] reported a case basilar invagination with AAD with absent posterior elements of C2 (absent lamina and spinous process and rudimentary pedicles of C2) in an 8-year old male child presenting with progressive myelopathy. None of the reported cases showed evidence of degenerative disc disease, as seen in our cases.

Embryologically, the second spinal sclerotome forms the posterior arch of axis. Furthermore, the development of the axis occurs in three stages, that is, precartilage, chondrification, and ossification stages.[10] During the precartilage stage (8 preovulatory weeks or Stage 23), cells of the sclerotome migrate in three different directions: ventromedially (surrounds the notochord and forms the vertebral body), dorsally (to form the neural arch from which the pedicles and articular process and lamina develops) and ventrolaterally (to form the transverse process and foramen transversarium). At about 6th week of embryogenesis, the chondrification stage of posterior arch begins at the pedicle and ends in the midline during the 4th month. Then, the ossification of this cartilaginous arch begins and usually completes by 3–4 years of age.[10] Therefore, a developmental defect in the posterior elements of the axis, as seen in our case, implies a very early fault in embryogenesis (either in the chondrification phase or failure of the ossification process).

Passias et al.,[3] reported a case of segmental ossified posterior longitudinal ligament (OPLL) at the C2-C3 disc space, together with the invagination of bilaterally hypoplastic lamina of the axis vertebrae into the spinal canal. They hypothesized that deficiency in the posterior structures of the axis resulted in an increased mechanical loading of the anterior elements, contributing to the development of OPLL at C2-C3 disc level. As seen in [Table 1], instability in conjunction with deficiencies of the posterior elements of the axis, typically manifested as anterolisthesis of C2 on C3, which was not seen in our patient. This anterolisthesis may or may not be associated with AAD or basilar invagination. In our case, the absence of C2 posterior elements with no facetal articulation between C2 and C3 along with occipitalized atlas led to increased motion brunt on the C2-3 disc that degenerated early and caused C2-3 instability. Enlargement of posterior process of C3, as seen in our case, was probably the result of compensatory mechanism for the absent spinous process of the axis, providing attachment to interspinous ligament and paraspinal muscles, described in literature by Srivastava et al.[2]

In a literature review, surgical stabilization was recommended in such patients with a good functional outcome. In view of the presence of myelopathy and instability at C2-3, our patient underwent an occipitocervical fixation [Figure 4] using the contoured rod and lateral mass screws.

In conclusion, the absence of C2 posterior elements is extremely rare and can lead to C2-3 instability at a young age. Surgical treatment is successful and is associated with a good outcome.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Deepak AN, Salunke P, Kamble RP. Case of atlantoaxial dislocation with assimilated C1, absent posterior C2, butterfly C3, and fused subaxial cervical spine: Management dilemma with multiple segmentation and formation defects. J Pediatr Neurosci 2017;12:72-4.  Back to cited text no. 1
[PUBMED]  [Full text]  
2.
Srivastava SK, Nemade PS, Aggarwal RA, Bhoale SK. Congenital absence of posterior elements of C2 vertebra with atlanto-axial dislocation and basilar invagination: A case report and review of literature. Asian Spine J 2016;10:170-5.  Back to cited text no. 2
    
3.
Passias PG, Wang S, Wang S. Combined ossification of the posterior longitudinal ligament at C2-3 and invagination of the posterior axis resulting in myelopathy. Eur Spine J. 2013;22(Suppl 3):S478-86.  Back to cited text no. 3
    
4.
Van Gilder JC, Menezes AH. Craniovertebral junction abnormalities. Clin Neurosurg 1983;30:514-30.  Back to cited text no. 4
    
5.
Behari S, Kiran Kumar MV, Banerji D, Chhabra DK, Jain VK. Atlantoaxial dislocation associated with the maldevelopment of the posterior neural arch of axis causing compressive myelopathy. Neurol India 2004;52:489-91.  Back to cited text no. 5
[PUBMED]  [Full text]  
6.
Goel A, Gupta S, Laheri V. Congenital absence of posterior elements of axis: Areport of two cases. Br J Neurosurg 1999;13:459-61.  Back to cited text no. 6
    
7.
Morizono Y, Sakou T, Maehara T. Congenital defect of posterior elements of the axis. Clin Orthop Relat Res 1987;216:120-3.  Back to cited text no. 7
    
8.
Muzumdar DP, Goel A. C2 over C3 spondyloptosis in a case with absent posterior elements: Report of an unusual case and analysis of treatment options. J Clin Neurosci 2004;11:675-7.  Back to cited text no. 8
    
9.
Trivedi P, Vyas KH, Behari S. Congenital absence of the posterior elements of C2 vertebra: Acase report. Neurol India 2003;51:250-1.  Back to cited text no. 9
[PUBMED]  [Full text]  
10.
O'Rahilly R, Muller F, Meyer DB. The human vertebral column at the end of the embryonic period proper. 2. The occipitocervical region. J Anat 1983;136:181-95.  Back to cited text no. 10
    


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