Thoraco-Lumbar Junction Disc Herniation and Tight Filum: A Unique Combination?

Purpose: The incidence of both symptomatic thoraco-lumbar junction disc herniation (TLJDH) and tight filum (TF) may be underestimated. Both conditions have a complex clinical presentation that may involve the distal spinal cord, conus medullaris, and/or cauda equina, including upper and/or lower motor neuron impairment, sensory impairment, urological and sexual dysfunction. The coexistence of both conditions has not been previously reported and may be a diagnostic and therapeutic challenge. Methods: We report three teenage girls, a 24-year-old woman, and two middleaged women who were diagnosed with both conditions and treated at our institution. Results: Disc herniation level was T11-T12 in 2, T12-L1 in 3, and L1-L2 in one. All patients had a fatty filum (n = 5) and/or a low-lying CM (at or above L1-L2 in 2, at or below L2-L3 in 4), and were treated with filum sectioning first. All patients noted marked improvement of preoperative complaints including back pain (n = 5), leg pain and fatigue (n = 4), urological complaints (n = 4), and toe gait (n = 1). One 16-year-old girl successfully underwent a thoracoscopic microdiscectomy for persisting pain at the thoraco-lumbar junction two years after filum sectioning. Conclusions: Thoraco-lumbar junction disc herniation and tight filum both act on the distal spinal cord close to the transition to the cauda equina. Both conditions may coincide and may even act synergistically, the disc herniation acting as a fulcrum, aggravating the deleterious effect of the tethering force (and vice versa). This might explain why both conditions combined may present at a younger age. We suggest filum sectioning as the primary treatment option in all patients, however, more cases and a longer follow-up are needed to better understand their unique combination and interaction. Nevertheless, when confronted with a symptomatic TLJDH especially in young patients we advise to rule out a coinciding TF by careful consideration of all clinical, radiological, and urological data.