Intraradicular extruded disc herniation as a rare cause of failed back surgery - case report and review of the literature.

We report an unusual case of intradural intraradicular lumbar disc herniation, in which an extruded fragment of disc was found within the sheath of the left S1 nerve root. Previous surgery of our patient in another medical centre was not beneficial. The diagnosis of intraradicular extruded disc herniation was made at the time of surgery during exploration of the L5-S1 disc space. Although magnetic resonance imaging is a useful diagnostic tool in all patients with lumbar disc herniation, preoperative correct diagnosis is usually difficult, as occurred in our patient. A careful observation of the root during surgery is indicated to detect such an anatomical abnormality, especially in cases with recurrent disc herniation.