Intradural disc a diagnostic dilemma: Case series and review of literature

Introduction: We present a case series of six cases of intradural disc herniation at L4–L5 level diagnosed on the basis of intraoperative findings. Result: All our cases, on preoperative magnetic resonance imaging (MRI) were reported as having diffuse annular bulge with large posterocentral extrusion. Our study comprised patients in age group of 30–60 years. Four cases out of six presented with cauda equina syndrome. In three cases, cauda equina was associated with sudden deterioration in the power of lower limb muscle groups. Discussion: We suspect that intradural herniation of disc was synchronous with cauda equina syndrome in these cases, which was very well documented in one of the cases. On retrospective analysis, MRI findings of mass effect in the form of displacement of the traversing nerve roots due to large central disc with crumble disc sign were suggestive of early evidence of intradural disc herniation. Y sign in ventral dura due to splitting of ventral dura and arachnoid mater by disc material was a good diagnostic sign to suspect intradural extra-arachnoid disc. The presence of hypointense structure inside the dura with no continuity with the adjacent intervertebral disc on MRI was highly suggestive of an intradural disc. Conclusion: Intradural disc prolapse remains a diagnostic dilemma as it is very difficult to diagnose all the cases preoperatively. The presence of above-mentioned radiological signs on MRI in patients having the large central disc on MRI, especially at L4–L5 levels, should raise suspicion of intradural herniation of disc.