Evidence of neuronal loss and granule cell axon reorganization in the dentate gyrus of cats with temporal lobe epilepsy-like seizures.

OBJECTIVE

To determine whether some cats with epilepsy and temporal lobe epilepsy (TLE)-like seizures have dentate gyrus neuropathologic changes consistent with TLE, including hilar neuron loss and mossy fiber sprouting.

METHODS

Postmortem hippocampal tissue from 5 cats with a history of seizures and 6 control cats was evaluated. Nissl-stained sections were used to estimate hilar neuron populations within the dentate gyrus by optical fractionator stereology. Timm-stained sections were scored by masked investigators to assess mossy fiber sprouting. Hippocampi from epileptic cats were evaluated bilaterally, and findings were compared with control cats.

RESULTS

Mean hilar neuron counts were lower in epileptic cats than controls, although this difference was not statistically significant. Two epileptic cats had hippocampal hilar neuron counts more than 2 SDs below the control mean. Mean Timm scores were higher in epileptic cats than controls, and 2 epileptic cats had mossy fiber sprouting scores more than 2 SDs above the control mean. One epileptic cat had both marked left-sided hilar neuron loss and severe mossy fiber sprouting, greatest in the left hippocampus.

CONCLUSIONS

The study found that 1 epileptic cat with TLE-like seizures had dentate gyrus neuropathologic changes resembling those described in TLE in humans and other animal models.

CLINICAL RELEVANCE: These findings support naturally occurring feline TLE as a potential clinical entity, and antemortem diagnostics should be investigated to identify these cats for advanced treatment options, such as surgical or laser ablation of the affected hippocampus.