Stereotaxic Implantation of Calibrated Pd109 and Y90 Spheres: A Technique for Producing Predictable Subcortical Lesions in the Brains of Laboratory Animals ‡§

When Horsley and Clarke8 introduced their stereotaxic manipulator in 1908, all subcortical areas in the brains of laboratory animals theoretically became accessible for study. As a consequence, many valuable data have been obtained from stimulation and ablation studies. The potential of the technique for ablation study has been limited for want of a necrotizing agent that would gradually destroy a predictable volume of tissue. In 1952, Carpenter and Whittier4 reviewed the work of others and demonstrated that stereotaxically implanted radon seeds create a more discrete lesion than any of the chemical, electrolytic, mechanical, or thermal methods. Others had explored the possibility of utilizing radium emanations, but never perfected it as an adjunct for stereotaxic surgery. Edwards and Bagg,5 in 1923, were probably the first to demonstrate that subcortically placed radon caused localized destruction with minimal disturbance of contiguous and overlying structures. They used a free-hand applicator for placement. Stein and Peterson,1' after stereotaxic implantation of a radon seed in the mesencephalon of a rhesus monkey, suggested in 1950 that this methodology might prove to be a useful adjunct to neurophysiological research and, eventually, to clinical neurosurgery. In 1951, Borison and Wang' destroyed the vomiting center of the dog by free-hand placement of radon seeds in the medulla oblongata. Their study was the first to demonstrate a correlation between radiation strength and lesion size in the central nervous system. These authors also pointed out that the gradual development of necrosis resulting from the radiation effect had a distinct advantage