Ossification of the Posterior Longitudinal Ligament

Pathogenesis, Management, and Current Surgical Approaches: A Review

Zachary A. Smith, M.D.; Colin C. Buchanan, M.D.; Dan Raphael, P.A.-C.; and Larry T. Khoo, M.D.

Disclosures

Neurosurg Focus. 2011;30(3):e10 

In This Article

Natural History and Clinical Presentation of OPLL

The PLL extends from the occiput to the sacrum along the posterior aspects of the vertebral bodies and the dorsal aspects of each intervertebral disc. As it becomes hypertrophied and ossifies, it results in a significant restriction of the cervical canal diameter. This compresses the spinal cord and leads to ischemia and myelopathy. In addition to this direct compression, repeated impacts of the ventral cord over the hypertrophied and ossified ligament can further lead to damage to the cord parenchyma.[66] As the most common site of ossification is in the cervical cord, cervical myelopathy is the most common presentation. However, clinically significant ossification of the ligament has also been noted to occur in the thoracic and lumbar spine.[1,19,46,50,51] Ossification of the PLL can present with pain, neurological deficit, or with acute neurological injury (even after a minor injury). However, given the prevalence of OPLL, the majority of patients with OPLL remain without significant symptoms. Another subset of patients with progressive OPLL may present with "clinically silent" myelopathy that is not associated with axial neck pain or radiculopathy.

A firm understanding of the natural history of OPLL is important. This is especially important for asymptomatic patients who have the potential to develop signs of myelopathy with time. In a study of 359 patients who underwent follow-up for a mean of 17.6 years, Matsunaga et al.[40] reported that 55 (17%) of 323 asymptomatic patients would eventually demonstrate examination findings of myelopathy. In 23 (64%) of the 36 patients with preexisting myelopathy, there was evidence of progression in their clinical examination. In a more recent radiographic study, Matsunaga et al.[41] studied radiographic progression in 167 patients following surgical treatment. Axial radiographic progression was seen in 70 (42%) and craniocaudal extension in 144 (86%) during follow-up.

Given this natural history of progression, it is our practice to consider patients for surgery when there is notable compression of the cervical spinal cord or T2 signal changes on MR imaging and evidence of clinical deterioration on physical examination.

These patients have often been observed using serial imaging and have been found to have progression of their disease. These patients are particularly younger and have few associated comorbid conditions. It is our belief, in common with several study groups in Japan and other Asian countries, that surgical decompression in these patients may prevent the development of progressive myelopathy and quadriparesis. However, in patients with radiographic progression without new clinical signs or symptoms, continued clinical follow-up is suggested.

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