Hemorrhagic Ligamentum Flavum Cyst in the Adjacent Level of Lytic Spondylolisthesis - A Case of Diagnostic and Therapeutic Dilemma.

INTRODUCTION: Occurrence of hemorrhagic cyst inside ligamentum flavum is a very rare phenomenon and presents with back pain, radiculopathy, or neurogenic claudication. Various causes reported in the literature are trauma, anticoagulant therapy, and increased micromotion in the setting of unstable and degenerated motion segment.

CASE REPORT: We report a case of 41-year-old male patient who presented with claudication pain in both lower limbs for the past 6 months associated with bilateral calf atrophy. Plain radiograph with dynamic films showed lytic spondylolisthesis at L4-L5 level. Magnetic resonance imaging revealed a hemorrhagic cyst inside ligamentum flavum at the L3-L4 level occupying the posterior epidural space severely compressing the thecal sac. After a thorough diagnostic and therapeutic work up, we did a midline sparing decompression of L3-L4 level under microscope without fixing the listhetic segment. The patient had significant pain relief after surgery and doing well till now.

CONCLUSION: In general, hemorrhagic cyst of ligamentum flavum is seen in a degenerated lumbar spine at the areas of increased micromotion and instability. Our case has shown that it can also occur in an adjacent segment of spondylolisthesis or instability. The obvious finding like listhesis in the adjacent segment may hinder a spine surgeon from diagnosing the cyst component and may guide to a erroneous treatment outline. Hence, it should not be missed in the imaging.