Ossification of the cruciform ligament of atlas; a rare cause of cervical myelopathy: Case report and review of literature

We present a case of cervical myelopathy secondary to ossification of the cruciform ligament (also known as cruciate ligament). This is a rare phenomenon that, to the best of our knowledge, has only been reported 16 times previously in literature. We have added a review of literature after our case presentation. We hope that by doing so, we may aid clinicians reach early diagnosis so as to be able to better manage this rare disease.

Key-words:

Cruciform ligament - ossification - spine

Introduction

Ossification of the cruciform ligament (also known as cruciate ligament) of atlas is a rare phenomenon.[[1]],[[2]],[[3]],[[4]] To the best of our knowledge, there have been only 16 cases reported in literature thus far. In this article, we present a case of cervical myelopathy secondary to ossification of the cruciform ligament of atlas. We have also provided a concise review of literature pertaining to this pathology.

Case Report

A 48-year-old male presented to our neurosurgery clinic with a complaint of pain in the bilateral lower limbs along with progressive weakness in all four extremities for the past 4 years as well as urinary incontinence for the past 1 year. He became bed bound and catheter dependent. He was treated for suspected cervical spine tuberculosis for 6 months by antituberculosis therapy at an outside institute, but there were no confirmatory tests done. He did not provide us with any other relevant history.

On examination, he was a middle-aged male with a body mass index of 30 kg/m 2 and wheel chair bound. He was alert, awake, and oriented to time, place, and person. He did not exhibit any cranial nerve deficits. His motor examination showed normal bulk, increased tone, and power of 0/5 in all muscle groups of both upper and lower limbs bilaterally. He also had hyperactive deep tendon reflexes of the biceps, triceps, brachioradialis, patellar, and Achilles tendons. Planters were up going along with sustained clonus bilaterally. Anal tone was lax.

Computed tomography (CT) scan [[Figure 1]] and [[Figure 2]] showed ossification of the entire cruciform ligament along with pseudarthrosis of C1 and C2 vertebra. Magnetic resonance imaging (MRI) [[Figure 3]] revealed severe cervical cord stenosis.

Figure 1: Computed tomography axial section showing ossification of the entire transverse ligament

Figure 2: Computed tomography scan, sagittal image showing pseudoarthrosis of atlas along with ossification of longitudinal band of cruciform ligament

Figure 3: T2 magnetic resonance imaging cervical spine sagittal section showing severe cord compression. Unidentified bright object in spine visualized in the magnetic resonance imaging was most likely secondary to ligament hypertrophy

The patient was explained in detail about the following three options: prolonged application of hard collar, halo ring traction, and surgical decompression. Due to chronic nature of his symptoms and belonging to a remote area making regular follow-ups difficult in case of halo traction and hard collar, the patient opted for surgical decompression. He was counseled about the risks including but not limited to cervical cord injury, visceral injury, failed decompression, and persistence of symptoms. After developing an understanding on risks and benefits, informed consent was taken and we did a neuronavigation-guided transoral decompression of C1 and C2. Highly vascular pseudarthrosis along C1 and C2 anterior arches and ossification of cruciate ligament (both transverse and longitudinal components) were noticed. Maximum safe debulking was performed.

Due to the main bulk of the ossified ligament seen anterior to the cord as well as the anterior compression of the cervical spine, we opted for an anterior approach as opposed to a posterior or 360 approach. Our patient and his family were kept in confidence that there may be a need of another procedure if complete debulking could not be done anteriorly.

Postoperative CT [[Figure 4]] and [[Figure 5]] scan was also performed which showed nonvisualization of the anterior tubercle, anterior arch, part of posterior arch of the atlas, and dens and pedicle of axis vertebra, with resultant widening of the spinal canal. Postoperative MRI was not done as the patient showed subjective and objective improvement. He had severe financial issues and MRI is a costly investigation in our country.

Figure 4: Postoperative computed tomography scan showing removal of most of the transverse ligament

Figure 5: Postoperative sagittal image revealing excision of pseudarthrosis bone and ossified longitudinal band

He was shifted to the intensive care unit for 24 h postoperatively and later shifted out. His neurological signs improved after 2 weeks with a power of 4/5 in the left hand and 3/5 both proximally and distally in left the lower limb, right upper limb, and lower limb. He had no pain or any other postoperative complication. Physiotherapy and rehabilitation program were initiated. On 3-month follow-up, he was able to stand with support and his motor examination improved to 4+ power in all groups bilaterally in both upper and lower limbs.

Discussion

Ossification of the atlantal ligament was first described in literature in 1978 by a case report on two patients by Wackenham.[[5]],[[6]] Another three cases were then published in 1979 by Dietemann. Please note that the above-mentioned articles were only available in French and we, to the best of our efforts, were unable to find full-text English translations. They have therefore not been included in [[Table 1]] that contains a summary of cases of atlantal ligament ossification reported in the literature to date.

Table 1: Previously published case reports available in English text on ossification of the atlantal ligaments

Table 1: Contd...

Cervical canal stenosis is a rare occurrence at the level of the atlas. This is due to a protective regional anatomy. The canal diameter at the retrodental level is around 17–25 mm, whereas the spinal cord diameter is between 10 and 12 mm. Consequently, for compression to occur at, this level would require a significantly large lesion or a compromise of the bony canal (congenital anomalies, trauma, intervention).[[6]],[[7]]

Ossification of the atlantal ligament may be due to calcium phosphate metabolic disease, obesity, diabetes mellitus, aging, and dynamic factors such as trauma.[[8]],[[9]] High amounts of fluoride have also been suggested as a possible cause by Wang et al.[[5]] A possible etiological cause in our patient could not be recognized. Ossification of the atlantal ligament may also be associated with other developmental anomalies at the craniovertebral junction such as hypoplasia of the atlas.[[5]],[[7]],[[8]]

Clinically, the disease presents as neck pain, stiffness, and features of myelopathy.[[10]] Treatment is controversial and should be tailored to the severity of the patient's presentation. Wang et al.[[5]] reported success with conservative therapies such as hard collar and halo ring traction. Others favored surgical decompression.

[[Table 1]] provided detailed summary on the presentation, imaging findings, treatment, and prognosis of previously reported patients with ossification of the atlantal ligament.

Conclusion

We report a rare case of atlantal ligament ossification that presented to our institution in June 2018. Our patient was managed surgically and has shown improvement in his symptoms. We are hopeful that with further rehabilitation and physical therapy, he will continue to improve. By supplementing our case report with a review of literature, we hope to provide a detailed overview of this disease so as to help clinicians better manage this rare entity.

Declaration of patient consent

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

Conflict of Interest

There are no conflicts of interest.

Financial support and sponsorship

Nil.

• References

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Publication History

Article published online:
09 September 2022