title: Development of a large animal model for investigation of deep brain stimulation for epilepsy.
abstract: OBJECTIVE
  To better understand the mechanism of action of deep brain stimulation (DBS) for epilepsy and to investigate implantable device features, it is desirable to have a large animal model to evaluate clinical-grade systems. This study assessed the suitability of an ovine model of epilepsy for this purpose.
  
  
  METHODS
  Animals were anesthetized for surgery and 1.5 T MRIs collected. Unilateral anterior thalamic DBS leads, hippocampal depth electrodes and catheters were implanted using a frameless stereotactic system. Evoked responses and local field potentials were collected and stored for off-line analysis.
  
  
  RESULTS
  Despite limited neuroanatomic information for this species, it was possible to reliably implant leads into the target structures using MR-guided techniques. Stimulation of these regions produced robust evoked potentials within this circuit that were dependent on stimulus location and parameters. High-frequency thalamic DBS produced a clear inhibition of both spontaneous and penicillin-induced ictal activity in the hippocampus which far outlasted the duration of the stimulation.
  
  
  CONCLUSIONS
  These preliminary results suggest that the sheep model may be useful for further investigation of DBS for epilepsy. The demonstration of marked suppression of network excitability with high-frequency stimulation supports a potential therapeutic mechanism for this DBS therapy.
authors.affiliation: Medtronic Neuromodulation, Minneapolis, MN 55432, USA. paul.stypulkowski@medtronic.com
authors.forename: Paul H
authors.initials: PH
authors.lastname: Stypulkowski
authors.forename: Jonathon E
authors.initials: JE
authors.lastname: Giftakis
authors.forename: Tina M
authors.initials: TM
authors.lastname: Billstrom
mesh_terms: D000818:Animals; D046690:Deep Brain Stimulation / Q000295:instrumentation / Q000379:methods*; D004827:Epilepsy / Q000503:physiopathology / Q000628:therapy*; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology; D058542:Implantable Neurostimulators; D008279:Magnetic Resonance Imaging; D023421:Models, Animal; D010406:Penicillins / Q000494:pharmacology; D012756:Sheep; D013238:Stereotaxic Techniques; D013788:Thalamus / Q000187:drug effects / Q000502:physiology
chemical_list: D010406:Penicillins