Shrinkage of the brain during histological procedures with fixation in formaldehyde solutions of different concentrations.

The purpose of this study was to measure the shrinkage of the brain during fixation and the subsequent histological procedures. In neuropathology formaldehyde solutions are the most common fixative, but different concentrations are used. This may lead to uncertainty in connection with quantitative comparative studies, because of the possibility of different degrees of shrinkage. Three groups of five brains each were fixed in three different formaldehyde solutions containing 4% buffered solution, 10% and 12% solutions without additives, respectively. The further procedure to the final histological preparation was the same in all groups. The total shrinkage in volume was 48%, with no significant difference between the three groups. A significant difference appears in relation to the duration of fixation in the most concentrated formaldehyde solution. In all three groups the shrinkage due to the fixation was more than half of the total shrinkage. Finally, it is concluded that comparative quantitative studies on brains can be performed without regard to the technique after fixation in any of the concentrations of formaldehyde investigated.