The clinical manifestations of cervical posterior longitudinal ligament ossification are similar to those of cervical spondylosis and cervical spinal stenosis, starting at the age of 50-60 years, and as ossification worsens, patients mainly show symptoms of spinal cord compression and some also have symptoms of nerve root compression. Localized cervical manifestations include soreness and pain and limitation of posterior extension. Spinal cord compression manifests as chronic progressive spastic quadriplegia. The upper extremities are characterized by hypotonia, numbness, weakness, loss of flexibility, reduced grip strength, and atrophy of the interosseous muscles on one or both sides; the lower extremities show weakness in walking, numbness, spastic gait, unstable walking, resembling stepping on cotton, and hyperactive tendon reflexes of the extremities; others may show difficulty in urination and defecation, constipation, and urinary incontinence.