After a heavy snowfall in the winter of 2010, an elderly man in his 60s slipped and fell while trying to board a crowded bus and immediately felt numbness in his limbs and below his chest, and could not move his arms and legs. Another example is that last summer, a bus company employee fell after a drunken fall and woke up with loss of movement in his limbs, then partially regained movement in his lower limbs, but his upper limbs were never heard from again. How can a minor trauma lead to such serious consequences? The examination revealed that these cervical spine trauma patients have a common pathogenic basis – ossification of the posterior longitudinal ligament of the cervical spine.
I. What is ossification of the posterior longitudinal ligament of the cervical spine?
The posterior longitudinal ligament is located in the posterior part of the vertebral body in the spinal canal and extends from the cardinal spine down to the sacral spine. Posterior longitudinal ligament ossification is the formation of ectopic bone structures in the posterior longitudinal ligament under the action of many factors. OPLL mostly occurs in the cervical spine, less in the thoracic spine, and rarely in the lumbar spine.
What is the etiology of cervical OPLL?
The etiology and pathogenesis of cervical OPLL are still not well understood. However, studies have found that the following factors are involved.
1.Genetic factors
The single nucleotide polymorphism of the nucleotide pyrophosphatase (NAPPS) gene, Mssamichi et al. suggest that mutations in the human NPPS genotype may contribute to the development of OPLL, and that alterations in the TGF-β1, TGF3, and COL6A1 genes are also high-risk factors for the development of OPLL.
2. Dietary habits and abnormal glucose metabolism
Kazushi et al. conducted a controlled study of the dietary habits of 69 patients with OPLL and 138 normal people in Hokkaido, Japan, between 1998 and 2001, and the results of a questionnaire survey showed that people who preferred pickled foods such as kimchi and rice as their staple food had a significantly higher risk of developing OPLL. The risk of OPLL was significantly higher than those who favored the consumption of chicken and soy products.
In addition, the proportion of patients with a history of diabetes was significantly higher in the OPLL population than in the normal control group, and diabetes may be an important risk factor for the development of OPLL.
3, bone formation and bone resorption disorders
It has been found that the occurrence of OPLL is due to the systemic or local factors affecting the synthesis and distribution of hormones and growth factors related to bone metabolism, thus disrupting the balance of osteochondral formation and resorption, resulting in ectopic ossification of the posterior longitudinal ligament.
4, race, region, gender factors
The incidence rate of Caucasians is significantly lower than that of Caucasians. In terms of geographical distribution, OPLL is more common in the Asian continent, with a low incidence in Africa, Europe and the United States, and an incidence rate of 0.01% to 1.7% in Europe and America, accounting for 26% of patients with spinal cervical spondylosis. It is more common in Asia and Japan, with an incidence of 1.9% to 4.3%, and is the primary cause of spinal cord cervical spondylosis. The incidence is also higher in the eastern coast of China.
5.Intervertebral disc degeneration
As a result of intervertebral disc degeneration, instability between the vertebral body, pulling the fiber ring or surrounding ligament attached to the vertebral body, causing subperiosteal hemorrhage, hematoma infiltration into the posterior longitudinal ligament calcification or ossification is formed OPLL.
6.Mechanical stimulation
The anterior flexion, posterior extension and lateral flexion activities of the cervical spine and the protrusion of nucleus pulposus tissue directly lead to abnormal stress distribution of the cervical disc and increased tension of the posterior longitudinal ligament, and this mechanical stimulation of the posterior longitudinal ligament directly promotes the acceleration of the ossification process of the posterior longitudinal ligament.
Third, why does ossification of the posterior longitudinal ligament lead to spinal cord injury?
With the appearance of ossified tissue in the posterior longitudinal ligament, the spinal cord is directly compressed from front to back (Figure 1), resulting in compression and deformation of the gray matter of the spinal cord, which causes damage and necrosis of motor and sensory nerve cells, as well as demyelination of the white matter of the spinal cord due to compression, and during this progressive chronic course, if the compression injury increases, spinal cord necrosis may worsen or spinal cord softening lesions may occur.
Because the spinal cord tolerates and adapts to slowly progressive compression, the patient may be asymptomatic or have very mild symptoms for a significant period of time. However, after the compression of the nerve tissue exceeds the threshold of its tolerance, the nerve function can take a sharp turn for the worse.
Figure 1. CT and MRI of patients with cervical OPLL
IV. What kind of spinal cord damage can be caused by cervical OPLL?
1. Quadriplegia
During spinal cord shock, there is bradykinetic paralysis below the level of injury, with loss of motor, reflex and sphincter functions, loss of sensory planes and inability to verbalize urine and stool. Injuries to the upper cervical spine are spastic paralysis, while the lower cervical spine is spastic paralysis due to the destruction of the cervical expansion of the spinal cord and nerve roots.
2.Spinal cord hemisection syndrome
Also known as Brown-Sequard syndrome. The motor and deep sensation of the trunk and limbs ipsilateral to the plane of injury are lost, and the pain and temperature sensation of the contralateral limb are lost.
3.Anterior spinal cord syndrome
Severe pressure on the front of the cervical spinal cord can sometimes cause occlusion of the anterior central spinal artery, resulting in quadriplegia, with lower limb paralysis heavier than upper limb paralysis, but the lower limbs and perineum still maintain position and deep sensation, and sometimes even retain superficial sensation.
4. Pericentral spinal canal syndrome
Most of them occur due to cervical hyperextension injury. The cervical spinal canal undergoes drastic solvent changes due to cervical hyperextension, and the spinal cord is subjected to anterior and posterior compression by the folded ligamentum flavum, intervertebral discs or bone spurs, causing damage to the conduction bundles around the central canal of the spinal cord, which manifests as quadriplegia below the plane of injury, with the upper extremity heavier than the lower extremity, without sensory separation, and with poor prognosis.
V. Does cervical OPLL cause serious complications?
Cervical OPLL can cause serious complications and even life-threatening complications if it causes severe spinal cord injury.
Common complications include.
1, respiratory failure and respiratory tract infections
2.Infection and stones in the genitourinary tract
3, bedsores
4, body temperature disorders
VI. Treatment
Treatment includes non-surgical treatment and surgical treatment.
1.Non-surgical treatment: bed rest, cervical brace fixation, anti-inflammatory and analgesic, nerve nutrition.
Massage and traction are prohibited.
Indications: only neck and shoulder pain, or with slight nerve root or spinal cord damage; posterior longitudinal ligament spinal canal occupancy less than 30%, myelogram no obvious obstruction; other reasons can not tolerate surgery.
It is important to note that ossification of the posterior longitudinal ligament is a progressive pathological process. It should be reviewed regularly during the conservative treatment, and once the compression on the spinal cord is found to be significantly aggravated, active surgery should be performed.
2.Surgical treatment
Surgery is divided into anterior cervical surgery and posterior cervical surgery.
Indications: severe symptoms, obvious ossification, sagittal diameter of the spinal canal is less than 12mm, and the spinal cord is obviously compressed on imaging. Conservative treatment is ineffective, the symptoms are aggravated; ossification foci are obvious, and minor trauma can cause spinal cord injury.
3, anterior cervical and posterior cervical surgery indications.
Indications for anterior cervical surgery: segmental ossification of the posterior longitudinal ligament below cervical 2-3, thickness of ossification foci less than 5 mm, spinal canal stenosis rate less than 45%.
Indications for posterior cervical surgery: continuous or mixed type of posterior longitudinal ligament ossification in more than 3 segments; ossification foci of posterior longitudinal ligament involving cervical 1 to 2 or involving cervicothoracic junction area; ossification foci of posterior longitudinal ligament accompanied by acute cervical spinal cord injury.
VII. Prognosis
The outcome depends on the degree of preoperative spinal cord injury, the rate of progression of the disease, age, and general condition of the body. Due to the poor ability of spinal cord tissue to repair and regenerate itself, if the spinal cord injury is severe and has been in an irreversible process, it is difficult to restore neurological function after surgery.