Abstract
A new unbiased stereological estimator, the rotator, was used to estimate the mean volume of pigmented substantia nigra (SN) neurons in three Parkinson's disease (PD) brains and age-matched controls. Average pigmented neuron volume was 31,300 microns 3 (5200) in controls and 28900 microns 3 (120) in patients. Estimating the absolute size distribution, revealed that PD patients had approximately 80% less total SN pigmented volume than controls. Compared with biased methods, in addition to dramatic improvements in efficiency and accuracy, results obtained by the unbiased rotator suggest that primarily the largest pigmented neurons in SN are lost in PD.