A STEREOLOGICAL METHOD FOR ESTIMATING THE TOTAL LENGTH AND SIZE OF MYELIN FIBERS IN HUMAN BRAIN WHITE-MATTER

A practically unbiased stereological method to obtain estimates of the volume and total length of nerve fibers in brain white matter is desc ribed. The sampling scheme is designed so that the majority of brain w hite matter is left intact, thus providing the possibility for resampl ing and further analysis. Uniform sampling of one complete hemispheric al white matter is performed. The volume fraction of nerve fibers in w hite matter is estimated by point counting. The total length of nerve fibers was estimated from the product of the volume of white matter, o btained with the Cavalieri principle: and the fiber length density, ob tained from the isotropic, uniform random sections which were ensured by the isector. The size of nerve fibers was derived by measuring the profile diameter perpendicular to its longest axis. The influence of t he postmortem fixation delay on nerve fiber parameters was investigate d in one dog and one pig. The criteria for identification of nerve fib er profiles at light microscopy were evaluated using electron microsco py. (C) 1997 Elsevier Science B.V.