1. A method of selective data retention in an implantable medical device, the method comprising: initiating loop recording in an implantable medical device upon determination of a neurological event, wherein loop recording comprises storing a data record of a plurality of data records in a data structure, the plurality of data records representing information about determined neurological events, the data structure being a buffer wherein some data records of the plurality of data records stored on the data structure are selectively replaced as new data is received in the buffer; determining a priority index for the plurality of data records based on severity levels of the determined neurological events; and replacing older data records of the plurality of data records on the data structure with new data records according to the priority index, wherein the new data records selectively replace those data records in the data structure having the lowest associated priority index.