| الوصف: |
In a large series of 413 epilepsy surgical resections from the National Hospital, hippocampal sclerosis was the commonest pathology identified in 60% of cases. Microdysgenesis is a complex microscopic cortical malformation recognised in association with hippocampal sclerosis in epilepsy, but its incidence, relationship to hippocampal sclerosis and functional relevance to epileptogenesis remain unknown. This is largely due to a lack of well-defined diagnostic criteria. To address this a stereological quantitative analysis of several components of microdysgenesis was carried out. White matter, cortical and layer I neuronal densities (ND) were measured in 31 surgical temporal lobectomies using immunohistochemistry for neuronal marker NeuN. Patients with seizure-free postoperative outcomes showed significantly more microdysgenetic features, including high white matter ND (P 0.05) or layer I ND (P 0.05). Mean white matter ND of 2164/mm3 were observed in epilepsy patients. There was no correlation between layer I and white matter ND suggesting that they may represent separate developmental abnormalities. Abnormal patterns of cortical myelination were also identified in microdysgenesis. Cyto-architectural abnormalities in analysis of 206 hippocampal specimens included disorganisation of dentate granule cells in 40% and cytoskeletal abnormalities in residual hilar cells in 55%. Granule cell disorganisation correlated with the degree of hippocampal neuronal loss suggesting an acquired rather than developmental lesion. Stereological quantitation of granule cells showed an overall cell loss, but greater numbers in regions of disorganisation, which may indicate enhanced neurogenesis. Quantitation of Cajal- Retzius cells showed increased numbers in hippocampal sclerosis and microdysgenesis compared to controls. Abnormalities in the cyto-architectural distribution of inhibitory interneurones were observed in microdysgenesis and focal cortical dysplasia in epilepsy, which may represent adaptive changes. In summary, the findings suggest that microdysgenesis may be a significant lesion in temporal lobe epilepsy in terms of post-surgical prognosis and quantitation allows a more precise definition. Increased Cajal-Retzius cells in hippocampal sclerosis and microdysgenesis may indicate a common developmental process involving the reelin pathway. |
