A patient with spastic paraparesis. MR and CT imaging demonstrated a plaque of bone in the anterior aspect of the thoracic spinal canal causing cord compression.
The patient presented with a 6-month history of unsteady gait. On examination there was a spastic paraparesis with a sensory level at the upper thoracic level.
Magnetic resonance imaging of the thoracic spine (Fig. 1) showed a confluent, vertically-orientated plaque of bone posterior to the T1, T2 and T3 vertebral bodies, indenting the theca and compressing the spinal cord. CT imaging (Fig. 2) confirmed the presence of an extensive plaque of cortical and cancellous bone in continuity with the T1, T2 and T3 vertebral bodies and defined its precise relationship to the spinal canal. Ossification of the anterior aspect of the upper thoracic vertebral bodies, typical of co-existent diffuse idiopathic skeletal hyperostosis (DISH), was also present.
The patient underwent an uneventful posterior decompression laminectomy.
Ossification of the posterior longitudinal ligament (OPLL) is an uncommon condition in which cortical or cancellous bone develops in the vertically orientated ligament. It is most prevalent in Japan and is most commonly diagnosed in the 5th and 6th decades, affecting males and females in a ratio of 2:1. Its aetiology is unknown although a wide variety of possible causative factors have been suggested (1).
OPLL most commonly affects the cervical spine. It may be composed of several discrete foci of ossification or may be a continuous plaque. This ossific mass may be firmly attached to the posterior aspect of the vertebral bodies and intervertebral discs or be separated by intervening connective tissue. When OPLL contains cancellous bone this may be continuous with cancellous bone of the adjacent vertebral bodies. OPLL may be confined to one vertebral level or extend over several levels.
Although OPLL may be asymptomatic, a variety of symptoms and signs have been associated with this disorder: cord compression, radiculopathy and non-specific cervico-brachialgia have all been described (2).
Lateral radiographs of the spine (not shown in this case) show a characteristic ossified plaque along the posterior margins of the vertebral bodies. The extent of ossification and the degree of spinal canal encroachment are clearly demonstrated on CT.
On MR imaging cortical bone is seen as a band of low signal intensity between the vertebral body bone marrow and the dural sac on T1- and T2-weighted images. In those cases in which the plaque contains cancellous bone, the signal intensity of the mass parallels that of marrow in the vertebral body, with which it may be continuous (3).
OPLL should not be confused with other causes of vertebral and paravertebral ossification/calcification. The characteristic dense vertical bands of ossification in OPLL are readily distinguished from syndesmophytes in ankylosing spondylitis, which are confined to the annulus and most prominent in the anterolateral margins of the intervertebral disc. Ossification of adjacent ligaments associated with severe ankylosing spondylitis spares the PLL. Osteophytes due to degenerative intervertebral disc disease are most common in the anterolateral aspect of the vertebral column, are triangular in shape and are horizontally orientated. Paravertebral ossification associated with psoriatic and Reiter's spondylitis is usually related to the lateral margins of the vertebral bodies and discs and is most apparent on frontal radiographs. Similarly the ossification in DISH is anterolateral in distribution and therefore distinguishable from OPLL but, as in this case, these two conditions may coexist (1).
In summary, OPLL is an uncommon condition of the spine with a wide spectrum of clinical presentation and characteristic radiological findings that distinguish it from other causes of spinal calcification or ossification.
Ossification of the posterior longitudinal ligament
Based on the provided CT and MRI images, a plate-like or band-like high-density shadow or signal can be observed at the posterior margin of the vertebral body (in the corresponding segments of the cervical or thoracic spine, etc.). Locally, it appears similar to cortical bone signal, closely adhering to the posterior aspect of the vertebral body and protruding into the spinal canal. In some regions, relatively low-signal bands are visible and connected to the highly suspected bony signal (suggesting the presence of cancellous bone), showing continuity with the trabecular signal of adjacent vertebral bodies. The lesion compresses or approximates the dural sac, possibly causing signs of spinal cord compression. Combined with the patient’s clinical presentation of spastic weakness in the lower limbs (spastic paraplegia), this indicates potential spinal cord dysfunction.
Based on the imaging findings and the patient's symptoms, OPLL is considered the primary diagnosis.
Considering the patient’s age, clinical presentation (spastic paraplegia), and typical imaging features (large or band-like ossifications at the posterior vertebral margin protruding into the spinal canal, with local spinal cord compression), the most likely diagnosis is:
Ossification of the Posterior Longitudinal Ligament (OPLL)
If necessary to delineate the extent of ossification or assess the degree of spinal cord injury, further high-resolution CT reconstruction, MRI (such as T2-weighted images and MR myelography), or other auxiliary tests (e.g., neurophysiological examinations) may be performed. If one needs to rule out other rare causes or coexisting lesions, a pathological examination can be considered during surgery.
1. Conservative Treatment: For patients with mild symptoms or without significant progressive neurological deterioration, the use of bracing, physical therapy, non-steroidal anti-inflammatory drugs (NSAIDs), or neuroprotective agents may be considered to alleviate pain and slow disease progression. Neurological function should be closely monitored for any deterioration that would necessitate timely adjustments.
2. Surgical Treatment: In cases of pronounced spinal cord compression, progressive neurological decline, or severe spinal canal stenosis on imaging, decompressive surgery (such as posterior laminectomy or anterior resection of the lesion and fusion) may be considered. Postoperative internal fixation can help maintain spinal stability and reduce nerve compression.
After evaluating the degree of spinal cord compression and surgical indications, rehabilitation should be conducted under the guidance of a professional physician or physical therapist. The following example plan follows the FITT-VP principle (Frequency, Intensity, Time, Type, Progression, and Individualization):
The rehabilitation plan should be adjusted appropriately throughout the process according to the patient’s progress, physical capacity, and coordination. If increased pain, pronounced numbness, or new symptoms occur, the exercise regimen should be discontinued immediately, and a professional medical evaluation should be sought.
This report is intended as a reference analysis based on current imaging and clinical information, and does not replace in-person evaluation or professional medical advice. Specific treatment should combine the patient’s overall condition and specialized assessment by a qualified physician.
Ossification of the posterior longitudinal ligament
