Differential diagnosis of recurrent lumbar disc herniation and postoperative deformation by myelography. An impossible task.

A series of 44 patients with persistent or recurring sciatic pain after myelography and operation for disc herniation were remyelographed and reoperated. Patients with lesions at a new level or at the same level but on the opposite side presented no diagnostic problems. However, in patients with myelographic changes at the same level and on the same side as at the first operation, it was impossible to distinguish disc herniation from postoperative extradural scarring. This was true whatever myelographic sign or combination of signs was chosen.