Syringomyelia Secondary to Ossified Ligamentum Flavum Treated with Unilateral Approach and Bilateral Decompression: A Case Report

Syringomyelia is most commonly associated with Chiari malformation, tumors, trauma, or arachnoiditis; however, its occurrence secondary to ossification of the ligamentum flavum is extremely rare. A 51 year old woman presented with long-standing back pain, right leg pain, muscle spasms, and numbness in the thigh. Neurological examination revealed decreased pain and temperature sensation in the T10 dermatome and mild spasticity in the lower extremities. Magnetic resonance imaging demonstrated bilateral OLF at the T10–T11 level causing spinal canal stenosis and associated syringomyelia extending 73 mm longitudinally. Computed tomography confirmed fused type ossification of the ligamentum flavum according to the Sato classification, with a 49.3% reduction in anteroposterior canal diameter. The patient underwent a unilateral approach with bilateral decompression at T9–T10 and T10–T11. Postoperatively, clinical symptoms improved markedly, and follow-up imaging demonstrated regression of the syrinx and restoration of canal dimensions. This case highlights that thoracic ossification of the ligamentum flavum can rarely cause syringomyelia. Early surgical decompression, particularly unilateral approach with bilateral decompression, may result in both symptomatic improvement and radiological regression of the syrinx.