Dogs with idiopathic epilepsy and focal epileptic seizures lack hilar neuron loss and mossy fiber sprouting of temporal lobe epilepsy.

Dogs with focal idiopathic epilepsy do not demonstrate classic TLE neuropathology, limiting direct surgical treatment parallels.

This prospective descriptive study investigated whether dogs with idiopathic epilepsy and focal seizures exhibit neuropathological changes consistent with temporal lobe epilepsy (TLE) as defined by human criteria. Seven dogs with confirmed idiopathic epilepsy and focal seizure history were enrolled. Following euthanasia, brains underwent perfusion fixation, sectioning, and staining. Nissl staining with stereological cell counting was used to assess hilar neuron loss, while Timm staining evaluated mossy fiber sprouting—two hallmark features of TLE in humans and other animal models. Results demonstrated no statistically significant hilar neuron loss in any subject, and no significant left-right hippocampal asymmetry was detected (P = .259). Timm staining revealed no extensive mossy fiber sprouting, and no significant interhemispheric asymmetry was found (P = .054). While subtle seizure-associated hippocampal changes were noted, none met the threshold criteria for TLE classification based on human standards. The authors acknowledge that focal seizures were selected as the inclusion criterion due to their prevalence in human TLE, but suggest future studies should target dogs with MRI-detected hippocampal asymmetry, which may better identify a canine TLE equivalent. The clinical significance lies in the potential to expand treatment options: if TLE can be confirmed in dogs, surgical resection or laser ablation could become viable alternatives for refractory epilepsy patients. This study represents an important step in understanding species differences in epilepsy neuropathology and the translational limitations of applying human diagnostic criteria to veterinary patients.

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