Anatomical alterations of the subthalamic nucleus in relation to age: a postmortem study

The subthalamic nucleus (STN) is currently the preferred target for chronic electrical high-frequency stimulation in Parkinson's disease. Anatomical determination of the exact position of the STN in the individual patient, using magnetic resonance imaging, remains cumbersome, whereas calculation of the target using a stereotactic atlas bypasses patient interindividual variations in the exact delineation of the STN. The aim of this study was to demonstrate variations in shape and position of the STN during life. In this anatomopathological study, a method was applied to localize the STN in reference to the anterior commissure-posterior commissure line (AC-PC line) in 12 postmortem brains of patients who died of non-neurological diseases. Their age varied from 29 to 84 years. Centers and borders of the STN were macroscopically measured in three spatial orthogonal planes in relation to the AC-PC line, and verified by light microscopy. The AC-PC distance remains almost constant during life (24.4 mm; SD 3.58). With increasing age, the center of the STN tends to move 3.9 mm cranially, 2.6 mm laterally, and 0.2 mm anteriorly. This last result also differs from the position mentioned in the stereotactic brain atlases. The form of the STN also changes. During life, the STN becomes wider in the mediolateral direction and smaller in the superior-inferior and anterior-posterior direction. The shape and spatial position of the STN also change during life. These changes should be taken into account during target determination in deep brain stimulation procedures in Parkinson's disease.