The median percent seizure frequency decrease (A) and the responder rates (B) are seen with VNS therapy at 3, 6, 12, and 24 months. Over time, the data shows a trend towards improved seizure outcomes in PTE versus non-PTE patients. When examining Engel outcomes clasess very little difference is found when comparing PTE and non-PTE patients at 3 months after VNS implantation (C). 24 months after VNS (D), patients with PTE exhibit Engel Class III more frequently and Engel Class IV–V less frequently, when compared with non-PTE patients. The number of patients is 254, 158, 154, and 71 for those with PTE and 1449, 975, 878, and 364 for those with non-PTE at 3, 6, 12, and 24 months, respectively. (From Englot DJ, Rolston JD, Wang DD, et al. Efficacy of vagus nerve stimulation in posttraumatic versus nontraumatic epilepsy. J Neurosurg. 2012;117(5):970–977; with permission.)