1616. Local vs. Systemic Amyloidosis as a Cause of Ligamentum Flavum Hypertrophy and Associated Spinal and/or Foraminal Stenosis

Authors: Bradley Steven Daniels, MD; Bryan Dalm, MD (Houston, TX)

Introduction: Amyloidosis is the extracellular accumulation of amyloid fibrils. Transthyretin is a transport protein synthesized by the liver. This protein can cause two types of amyloidosis – hereditary systemic amyloidosis and senile systemic amyloidosis. Spinal stenosis is a common cause of back and leg pain, particularly in the elderly. Hypertrophy of supporting ligaments, particularly the ligamentum flavum, are contributors to this condition. Amyloid has been noted in hypertrophied spinal ligaments of elderly patients. Recent studies have identified wild type transthyretin as the amyloid infiltrating the ligamentum flavum in patients with lumbar stenosis. We report a case of a patient presenting with symptoms of spinal stenosis and thoracic radiculopathy found to have calcification of the ligamentum of the thoracic spine which on pathology showed extensive WT-transthyretin indicating local vs. systemic amyloidosis. Methods: The record of a patient found to have amyloidosis of the ligamentum flavum causing spinal/foraminal stenosis was reviewed. Results: The patient is a 68 year old male with seronegative spondyloarthropathy and extensive surgical history to relieve spinal stenosis associated with this condition who presented with mid back and flank pain with neurogenic claudication. Pain management attempted a right sided T11-12 facet rhizotomy which improved his symptoms. Subsequently, the patient had a CT thoracic spine which showed foraminal stenosis at T11-12 due to calcification of the ligamentum flavum compromising the T11 nerve root. He underwent T11 laminectomy for removal of this lesion with concurrent medial T11-12 facetectomy and foraminotomy for decompression of the nerve root. At his postoperative visit, the patient endorsed resolution of his thoracic pain. Pathology of the removed ligamentum stained Congo red indicating amyloid. Subsequent study identified the amyloidosis as WT-ATTR (wild type transthyretin) type. Conclusion: Amyloid deposition should be considered in patients with spinal stenosis. There may be an association between spinal stenosis and systemic amyloidosis.