Supplementary Material for: Measuring Impact in Stereotactic and Functional Neurosurgery: An Analysis of the Top 100 Most Highly Cited Works and the Citation Classics in the Field N.Lipsman A.M.Lozano 2012 <b><i>Background:</i></b> Functional neurosurgery is a rapidly expanding field, with an exponentially growing literature. However, as with other fields, it can sometimes be difficult to distinguish between what is incremental and what is transformational. One way of measuring durable impact is examining the number of times a specific piece of scholarship is cited by others in the field. For example, papers that have been cited at least 400 times are designated ‘citation classics’ or works that, by virtue of very high citations, have been deemed of particular importance by researchers working in related disciplines. <b><i>Methods:</i></b> We queried a large, web-based scholarly database using 49 pre-selected search terms. The results for each individual query was manually examined for relevance to the functional neurosurgery field in order to arrive at the top 100 most highly cited papers as well as the citation classics. <b><i>Results:</i></b> The top 100 most cited papers, including 61 citation classics, in the stereotactic and functional neurosurgery field can be divided into 7 categories: functional/anatomic studies, technological innovations, and papers relevant to movement disorders, pain, psychiatry, radiosurgery and epilepsy. <b><i>Conclusions:</i></b> We have attempted to ascertain which papers have had, and continue to have, significant impact in our rapidly advancing field. At a minimum, the citation classics in functional neurosurgery provide both trainees and seasoned surgeons with a reading list of the ‘must-know’ works in the field – works whose influence have helped shape the direction of functional neurosurgery well into the future.