27To evaluate the localization of functional deficit area in epileptogenic zones of the 28 brain in seven refractory and seven non-refractory epilepsy dogs using technetium 99m 29 labeled with ethyl cysteinate dimer and interictal Single Photon Emission Computed 30 Tomography [ 99m Tc-ECD SPECT] co-registration with Magnetic Resonance Imaging (MRI). 31Regions showing perfusion deficits in the SPECT images were analyzed by using the standard 32 semiquantitative evaluation method to compare the level of cortical perfusion to the 33 maximum number of counts within the cerebellum (max C), considered the area of reference. 34This study showed that SPECT imaging revealed abnormalities in several regions of the brain 35 in both epilepsy groups. The refractory epilepsy dogs showed more frequency area of 36 hypoperfusion in temporal lobe than non-refractory group with not statistically significance 37 (p=0.28). The result suggests the lesion in temporal might be relevance with refractory 38 epilepsy in canine patients. 39 40 KEY WORDS: dogs, drug-resistant epilepsy, ethyl cysteinate dimer, single photon 41 emission computed tomography 42 43 44 45 46 47 48 52