The authors report the case of a 28-year-old woman who presented with L5 bilateral sciatica associated with perineal sensory disorders. During surgery, a mature pluritissular dysembryoma originating in a tethered spinal cord was discovered at the level of the L2-L3 intervertebral space. Following removal of the lesion, all symptoms disappeared. Mature pluritissular dysembryomas of the spinal cord result from the inclusion of neuroectodermal and mesodermal tissue which has not followed normal evolutive embryonic organization.