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Epidural Pressure Measurements: Relationship Between Epidural Pressure and Posture in Patients with Lumbar Spinal Stenosis

Study Design The relationship between epidural pressure and lumbar posture was assessed in patients with lumbar spinal stenosis. Objectives This study was performed to assess the relationship between epdural pressure and lumbar posture in patients with lumbar spinal stenosis. Methods The study was performed on 10 patients who had cauda equina symptoms at the L4–L5 level. The catheter transducer was inserted into the epidural space through L5-S1 interlaminar space and placed at the L4–L5 disc level. This transducer was connected with an amplifier and a recorder. Epidural pressure was continuously measured in various postures. Results Local epidural pressure at the stenotic level was low in lying and sitting postures, and high in standing postures. Pressure was increased with extension, but decreased with flexion. The highest pressure was 116.7±38.4 mm Hg in standing with extension. Conclusion Epidural pressure was significantly related to posture. These pressure changes correlated with the development of cauda equina symptoms. The increase of epidural pressure by posture may induce compression of the cauda equina. These pressure changes may explain the postural dependency in eliciting symptoms.