Thoracic myelopathy secondary to ossified ligamentum flavum

Background. Focal ossification of the ligamentum flavum (OLF) forms one of the rare causes of thoracic myelopathy. The lower thoracic spine is most fr equently affected and the patients present with initial posterior column di sturbances followed by progressively increasing spastic paraparesis. The pa thogenesis of OLF has not been conclusively established. Method. Five patients with thoracic myelopathy due to OLF underwent decompr essive laminectomy and excision of the ligamentum flavum. Their MRI delinea ted a linear or beak like excrescence, uniformly hypo-intense on TI and T2 weighted images, situated posterior to the thecal sac. A comparison between the preoperative neurological status and the status at follow-up was done using Harsh's myelopathic grading. Finding. Decompressive laminectomy followed by the drilling of the OLF and its excision, occasionally along with the adherent outer layer of the dura, resulted in significant improvement in motor weakness and tingling sensati ons. However, at the last available follow-up, none of the patients had ret ained their ability to run briskly (grade I) and all of them had residual s pasticity. Interpretation. OLF may significantly contribute to a spatial reduction of the thoracic spinal canal resulting in paraparesis. The T2 weighted sagitta l image of the magnetic resonance imaging (MRI) is the modality of choice f or screening of the longitudinal extent of the OLF. A rapid neurological im provement occurs following decompressive laminectomy and excision of the OL F. However, the persistence of residual spasticity at follow-up may be due to irreversible changes within the cord by the significant thecal compressi on and the delay between the onset of initial symptoms and signs and surgic al decompression.