Atlanto - Axial Instability with Cervical Myelopathy: A Case Study
A 75-year-old serviceman presented a complaint of severe pain in the neck lasting the past two years. He was having imbalances in walking and having difficulty in doing finer movements of hand for example: while writing, buttoning the shirt, eating, etc. He also had an increased frequency of urination in the last week. On questioning, he revealed that he suffered a spinal injury twenty years ago. The injury was due to a fall from a height. The case had received conservative treatment.
Furthermore, on examination, a posterior spinal tenderness at the upper cervical region came to light. When rotating neck, he experienced pain. Neurological examination pointed out to features of cervical myelopathy like positive Hoffman’s sign, Romberg’s sign, positive random walking test, and myelopathy hand. All the deep tendon reflexes depicted exaggeration with Babinski planter response. The clinical diagnosis pointed to cervical myelopathy due to the sequelae of an old trauma of the cervical spine.
Radiographs of the cervical spine showed an increase in distance between C1 anterior arch and the odontoid process of C2. Flexion- extension views of upper cervical spine showed instability. There was a subluxation of C1 over C2. The patients’ ESR had not risen and the rheumatoid factor was negative.
MRI of cervical spine showed features of myelomalacia at C1 region. The space available for the cord (SAC) was severely reduced to 6mm due to anterior subluxation of C1 and compression of posterior arch of C1. Axial cuts showed transverse ligament deficiency at C2. CT scan with reconstruction, a CT vertebral artery angiogram helped locate the position of vertebral arteries and to rule out their anomalies. Left vertebral artery was small in size non-dominant. This is an important step during the planning of any upper cervical spine surgical intervention.
Considering the patients’ age, general condition, advanced cervical myelopathy (Nurick Grade-3), we chose C1-C2 fixation and fusion. Following it, we had a pre-operative workup. C1 lateral mass fixation and C2 pedicle screw fixation was conducted followed by C1-C2 fusion in the reduced position. C1 posterior arch was excised to relive the pressure on the cord. The post-operative period was uneventful, the patient recovered well. Before discharge, he had to walk. He ended up, walking comfortably and was able to climb stairs with help.
On follow-up his finer hand movements showed an improvement, suggesting recovery from cervical myelopathy. We had to follow him up for a long period to look for further neurological improvement.
A note on history of C1- C2 fixation
Attempts at surgical stabilization of C1 and C2 from a posterior approach date to early 1910, when Mixter and Osgood described using heavy silk thread to wire the spinous processes of C1 and C2 together. The use of posterior cervical wiring of the lamina of C1 and C2 dates to 1939 in a report by Gallie. Brooks and Jenkins offered an alternative method of posterior C1-C2 laminar wiring in 1978. Dickman and Sonntag, et al further modified the posterior wiring technique in 1991.
In the 1980s inter-laminar clamps got popular as an alternative method of posterior C1-C2 fixation. Posterior screw fixation utilizing C1-C2 trans-articular screws and C1 lateral mass screws with C2 pars screws were the final two alternative methods of posterior C1-C2 fixation. The C1 lateral mass screw with C2 pedicle screw construct was initially created with plates and screws by Goel et al in the 1980s. Since then, the method has recently gained popularity.