Hydraulic spinal cord and cauda equina nerve injuries are very uncommon. Since 19 96, we have received and treated 4 patients with hydraulic spinal cord and cauda equina injuries. Thisrnreport gives a detail description.rnFour patients with hydraulic spinal cord and cauda equina nerve injuries, male: 3, female: 1, aging 13-56 years have been treated in our hospital since 1996. E xtradural blocking injury was in 1 patient, extradural anaesthesia injury in 1 p atient and intraspinal canal myelography injury in 2 patients; the segments of i ntraspinal canal were L2-3 and L3-4. One patient was accompanied b y femoral fracture, 2 patients by intraspinal tumor and 1 patient had operat ion because of prolapse of lumbar intervertebral disc.