Spinal and cranial contributions to total cerebrospinal fluid transport

In this study, we quantified cerebrospinal fluid (CSF) transport from the c ranial and spinal subarachnoid spaces separately in sheep and determined th e relative proportion of total CSF drainage that occurred from both CSF com partments. Cranial and spinal CSF systems were separated by placement of an extradural ligature over the spinal cord between C-1 and C-2. In one appro ach, two different radiolabeled human serum albumins (HSA) were introduced into the appropriate CSF compartment by a perfusion system (method 1) or as a bolus injection (method 2). Plasma tracer recoveries in conjunction with a mass balance equation were used to estimate CSF transport. In method 3, catheters connected to reservoirs filled with artificial CSF were introduce d into the cranial and spinal CSF compartments. Incremental CSF pressures w ere established in each CSF system, and the corresponding steady-state flow rates were measured. Total CSF drainage ranged from 0.51 to 0.75 ml.h(-1). cmH(2)O(-1). Expressed as a percentage of the total CSF transport, the rati os of cranial-to-spinal clearance estimated from methods 1, 2, and 3 were 7 5:25, 88:12, and 75:25, respectively. Primarily on the basis of the data de rived from methods 1 and 3, we conclude that the spinal subarachnoid compar tment has an important role in CSF clearance and is responsible for approxi mately one-fourth of total CSF transport.