Neurol India Home 

Year : 2019  |  Volume : 67  |  Issue : 6  |  Page : 1553--1555

Short Segment C1 - C2 Fusion in a Case of Congenital C2 Spondylolysis Associated with Chiari Malformation

Kokkula Praneeth, Pravin Salunke, Madhivanan Karthigeyan, Puneet Malik 
 Department of Neurosurgery, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India

Correspondence Address:
Dr. Madhivanan Karthigeyan
Department of Neurosurgery, Postgraduate Institute of Medical Education and Research (PGIMER), Sector 12, Chandigarh - 160 012

How to cite this article:
Praneeth K, Salunke P, Karthigeyan M, Malik P. Short Segment C1 - C2 Fusion in a Case of Congenital C2 Spondylolysis Associated with Chiari Malformation.Neurol India 2019;67:1553-1555

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Praneeth K, Salunke P, Karthigeyan M, Malik P. Short Segment C1 - C2 Fusion in a Case of Congenital C2 Spondylolysis Associated with Chiari Malformation. Neurol India [serial online] 2019 [cited 2020 May 28 ];67:1553-1555
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C2 spondylolysis which is defined as a congenital defect in the pars interarticularis, is occasionally described.[1],[2],[3] Rarely, it is part of the array of osseous segmentation defects seen in patients with congenital craniovertebral junction (CVJ) anomalies.[4] Knowledge of such anomaly is necessary for a neurosurgeon operating on the area of CVJ because the C2 instrumentation often involves the pedicle or pars interarticularis. In the presence of C2 pars defect, the surgical procedure commonly practised is occipito-cervical fusion, skipping instrumentation at C2 level.[3],[4] Here, we report a patient of congenital CVJ anomaly with C2 spondylolysis and Chiari malformation (type 1) who underwent successful short segment C1-C2 fusion. A 36-year-old man presented with symptoms of paresthesias and weakness of all four limbs and unsteadiness of gait of 6-month duration. He had spastic quadriparesis, loss of posterior column sensation and bilateral cerebellar signs. Magnetic resonance imaging (MRI) of CVJ revealed crowded posterior fossa and Chiari malformation type 1 with compression of cervicomedullary junction [Figure 1]. An associated syringomyelia was seen extending from C2 to C5 levels. Computed tomography (CT) showed dens violating the Chamberlain's line. There was a corticated defect seen in the pars interarticularis on the right side and lamina on the left side of C2 vertebra. A dynamic plain radiograph of CVJ showed no evidence of overt instability of C1-C2/C2-C3 [Figure 2]. The patient underwent bony foramen magnum decompression with posterior C1-C2 fusion. After midline incision and subperiosteal dissection, C1 and C2 posterior elements were exposed [Figure 3]. Initially, C2 nerve mobilisation was attempted. However, bilateral nerve roots had to be sacrificed to gain a panoramic view of the C1-C2 joint space.[5] The bilateral C1-C2 joints were opened, denuded of the articular cartilage and drilled. The joints were packed with spacers filled with autologous rib graft. Screws were placed in bilateral C1 lateral mass. In C2, pedicle screws were placed by choosing an entry point on the superior portion of the isthmus. Finally, the C1-C2 screw tulips were connected by rods. The cortical ends of the deficient C2 lamina and pars interarticularis were decorticated and packed with bone chips to augment the fusion of the posterior arch of C2 vertebra. Bony decompression of foramen magnum was performed without dural opening. A constriction band was noted over the dura which was released. Postoperative CT showed satisfactory placement of screws. However, at two weeks, the patient succumbed to a chest infection.{Figure 1}{Figure 2}{Figure 3}

Spondylolysis is defined as a congenital defect in the pars interarticularis of a vertebra.[1],[2],[3] This condition is most frequently seen in the lumbar spine. In the cervical spine, it is uncommon and usually an incidental finding, most often seen at the level of C6 vertebra.[2],[3] It can be either unilateral or bilateral and is more common in adults than in children.[1],[2]

Spondylolysis of C2 spine is occasionally described.[1],[2],[3],[4] It is due to primitive defect of chondrification of the mesenchymal precursor of the vertebral body and it is likely to be associated with spondylolysis at other vertebral levels or other segmentation anomalies elsewhere in the spine.[2],[3] Its presence is incidentally detected while evaluating a patient for neck pain or other non-specific complaints such as trivial fall, torticollis, clicks, numbness and weakness in the limbs.[1],[3] It can be mistaken for a fracture line and can be differentiated by smooth, well-corticated margins and absence of healing of the defect on follow-up imaging.[1],[2],[3] Most cases are conservatively managed with bracing devices. Surgical intervention is necessary when associated with instability, progressive deformity, neural compression due to cervical stenosis or while treating an associated C2 fracture.[2],[3] C2 spondylolysis in association with congenital CVJ anomalies is unusual.[4] Such congenital defect in conjunction with a symptomatic CVJ pathology assumes surgical importance.

Chiari malformation has been related to instability of the C1-C2 joint. Goel et al. has suggested C1-C2 fixation as a treatment modality in patients with Chiari malformation type 1 and has shown good clinical improvement in his patients.[6] Hence, we decided to perform C1-C2 fusion in our patient.

Once we had opted to address the underlying C1-C2 instability, the dilemma occurred in deciding the extent of fusion. In the absence of posterior elements of C2, studies have described occipitocervical fusion that extends caudally to the subaxial spine.[3],[4] In such cases, the C2 vertebra was not included in the construct. However, these extensive fixation techniques could lead to certain functional and long-term complications.[7] First, the long segment fusion would restrict neck mobility which can adversely affect the quality of life of the patient. The second reason owes to the biomechanical aspect of not including the C2 spine in the construct.[8] The C2 vertebra is a transitional zone that transmits the weight of the cranium to the subaxial spine. A long construct skipping the intervening C2 produces a long lever arm that is likely to fail in the long run due to a cantilever effect. Therefore, we preferred a short fusion with the forces that act close to the C1-C2 joint. In our patient, we performed C1-C2 short segment fusion using C1-C2 facetal screws. Owing to the C2 spondylolysis and laminar defect, a par or translaminar screw was not possible. The C2 screws were inserted directly into the C2 body. In addition, the defects in the pars and lamina were decorticated and packed with bone chips to augment fusion. The postoperative radiology confirmed satisfactory screw placement of C1-C2.

Though the majority of congenital C2 spondylolysis is asymptomatic, occasionally they can be associated with C2-3 listhesis.[2],[3],[4] Before proceeding with short segment C1-C2 fusion, such an instability needs to be excluded. In the presence of C2-3 subluxation, the fusion has to be extended to the subaxial spine.

There is only one case report in the English literature documenting the association of Chiari malformation with C2 spondylolysis.[4] The patient also had atlanto axial instability with inverted vertebral arteries on either side. The authors performed occipito-C3/C4 lateral mass screw avoiding the manipulating of C1-C2 joint and instrumentation in the C1-C2 vertebrae. Although it appears to be an alternative strategy, we considered direct C1-C2 fixation to be a more stable construct for the reasons mentioned above avoiding a cantilever effect and restriction of neck movements. Furthermore, the anomalous vertebral arteries are not a deterrent for C1-C2 joint manipulation and fixation.[9]

To summarise, congenital C2 spondylolysis with Chiari malformation is a rare entity. The pars defect at C2 does not preclude placement of C2 screws.

Compliance with ethical standards

Informed consent was obtained from the patient.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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