Single section and disector counts in evaluating neuronal loss from the substantia nigra in patients with Parkinson's disease.

In order to investigate the correlation between single section (SS) and disector (DS) counts for estimating the pigmented neurons in the pars compacta of the substantia nigra (SNpc), 12 patients with Parkinson's disease (PD) and seven controls were studied. The SS counts were obtained at the level of the exit of the third cranial nerve in the SNpc. The DS counts were made from the whole volume of the SNpc. There was a significant correlation between SS and DS counts (r = 0.94, P < 0.001), suggesting that the methods closely agree. Comparison of SS and DS counts in controls and PD patients showed that the pigmented neurons in PD were decreased by 75% (P < 0.001) and 55% (P < 0.001) in the SS and DS counts, respectively. This study suggests that loss of pigmented neurons from the SNpc in PD can be estimated by either method.