Myelopathy caused by hypertrophy of the posterior longitudinal ligament of the cervical spine in a patient with long-term hemodialysis

A 48-year-old female was admitted to our hospital because of progressive gait deterioration over a period of 4 months. She had been treated by hemodialysis for 14 years after bilateral nephrectomy. She originally suffered achondroplasia. Otherwise She was a healthy woman. Neurological examination showed weakness and hypesthesia below C-5, accelerated deep tendon reflexes and inability in walking. T-1 weighted magnetic resonance imaging revealed severe cord compression from C-4 to C-6 due to an epidural isointensity mass located in the ventral surface of the dura. This mass was enhanced by a contrast medium. Anterior decompression followed by an autogenous vertebral bone graft at C-4/5 and C-5/6 was performed. The posterior longitudinal ligament was remarkably thickened resulting in severe cord compression. Histologically this thick ligament contained amyloid deposition both in the superficial and deep layers. Ossification was not noticed in the ligament. Diagnosis of hypertrophy of the posterior longitudinal ligament (HPLL) was made. HPLL is known to be frequenthy associated with herniated intervertebral discs or segmental ossification of the posterior longitudinal ligament (OPLL). Myelopathy in this patient with long-term hemodialysis was aggravated by HPLL without ossification due to imbalance of systemic metabolism such as amyloidosis. The authors report a unique case of HPLL caused by amyloidosis as one of the complications of chronic hemodialysis with special emphasis on its pathophysiology and management.