One atlas - three anatomies: relationships of the Schaltenbrand and Wahren microscopic data.

The stereotaxic atlas of Schaltenbrand and Wahren is widely used for orientation in functional neurosurgery of the human diencephalon. As the sagittal, frontal, and horizontal microscopic series were gathered from three different cerebral hemispheres, loci with the same ACPC (anterior commissure-posterior commissure) coordinates are not exactly anatomically corresponding. We compared the 3-D position of 21 anatomical structures in the three series based on their digitally interpolated solid volume representations. Regression analysis of the centres of gravity revealed strong linear correlations between series (0.944< or = Pearson's r< or = 0.976, alpha<0. 0001). Thus calculation of anatomically corresponding sites based on the regression equations seems justified. Volumetry revealed that the sagittally sectioned thalamus is approximately 10% larger than the frontally and 40% larger than the horizontally sectioned thalamus. So as to match it to the sagittal series, the frontal series has to be widened in lateral direction by 19%, in anteroposterior and dorsobasal (vertical) direction it has to be compressed by 5 and 9%, respectively. In contrast, the distance of structures from the midline in the horizontal and sagittal series is very similar. The horizontal series is, however, 25% smaller than the sagittal one in anteroposterior and 17% in vertical direction. On average, thalamic nuclei in the right hemisphere of brain LXXVIII (horizontal microscopic series) were located 2 mm more anterior as compared with the left side (sagittal series), which fact may be explained by difference in size and/or asymmetry. Spatial overlap between corresponding thalamic nuclei from the three series amounted to only 0-28% when superimposed in the ACPC reference space. Linear transformation towards an average led to significant increase (0-37%, p<0.001) of the overlap and ameliorated the quality of the fit of thalamic borders. Limited increase of the overlap is in part due to pronounced differences in the size of thalamic nuclei between the series.