Intradural lumbar disc herniation. Report of three cases with a review of the literature.

Intradural lumbar disc herniation (ILDH) is rare. Three new cases of this condition are reported, adding to the 70 previously documented cases. An incidence of ILDH in between 0.04 and 0.33 percent of lumbar disc protrusions has been reported. More than one third of ILDH were observed at L1-2 to L3-4 levels, while only a tenth of cases occurred at L5-S1. The mechanism of ILDH is not known with certainty. Adhesions between the ventral wall of the dura and posterior longitudinal ligament could act as a preconditioning factor. A diagnosis of ILDH may be made with difficulty, and it is seldom suspected preoperatively. Prompt surgery is necessary because the neurologic prognosis appears to be closely linked with preoperative duration of neurologic symptoms.