A total of 151 subjects underwent screening prior to enrollment. Eight failed screening, and 143 went on to be randomized. Of those randomized, 8 subjects (4 in each of the treatment groups) were not treated. One patient in the VNS arm was explanted prior to initiation of device stimulation, so they were excluded. Therefore, 134 subjects were treated (ITT population): 65 were implanted with the VNS system and 69 were treated with AED. Nineteen investigational sites in the UK, Austria, Belgium, Germany, and Sweden participated in this study and enrolled subjects.