Clinical recording of pressure on the spinal cord and cauda equina. Part 1: the spinal block infusion test: method and clinical studies.

When an intraspinal expanding lesion causes a spinal block, a segment of the spinal cord or cauda equina will be subjected to general pressure from the surrounding tissue. This spinal block pressure, the spinal equivalent to intracranial pressure, was measured by lumbar infusion of fluid and simultaneous recording of the volume-pressure curve caudal to the block. The point of deviation from or breakthrough of the exponential volume-pressure curve indicated the spinal block pressure. Spinal block pressure of about 500 mm H2O and more could be determined by this method, and, when it was combined with Queckenstedt's test, lower pressures could be assessed as well. In the static (thoracic) part of the spine, spinal block pressure up to the level of arterial blood pressure was recorded. In the dynamic part of the spine, however, spinal block pressure could exceed arterial blood pressure due to external compressive forces during extension of the spine. There was a general tendency for more severe neurological deficits in patients with high spinal block pressure; but the duration of the pressure, additional focal pressure, and spinal cord compared with nerve root compression seemed equally important factors. The recording has implications for diagnosis, positioning of patients for myelography and surgery, selection of high-risk patients for the most appropriate surgical procedure, and detection of postoperative hematoma. There were no complications associated with the recordings.