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Microdysgenesis in temporal lobe epilepsy. A quantitative and immunohistochemical study of white matter neurones
M Thom1, S Sisodiya, W Harkness
1Department of Neuropathology, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK. M.Thom@ion.ucl.ac.uk
Abstract:
Microdysgenesis is a microscopic cortical malformation considered to act as a substrate for seizures in some patients with generalized epilepsy. It is also recognized to involve the temporal lobe in a proportion of patients with intractable temporal lobe epilepsy, but the incidence of this abnormality, its relationship to mesial temporal lobe sclerosis and relevance to epileptogenesis remain unknown. This is partly due to a lack of well-defined quantitative pathological diagnostic criteria. To begin to address these issues, we have carried out a rigorous quantitative analysis, using three-dimensional cell counting methods, of several components of microdysgenesis in temporal lobectomy specimens. White matter, cortical and layer I neuronal densities (NDs) were measured using immunohistochemistry for the neuronal markers neuronal nuclear antigen and calbindin D-28-K. Patients with a seizure-free outcome (Class I) showed significantly more microdysgenetic features including higher white matter ND (P < 0.05), particularly of small (<10 microm diameter) neurones (P < 0.01), higher layer I ND (P < 0.05) and increased numbers of Cajal-Retzius-like calbindin-positive neurones (P < 0.05). We also demonstrated that white matter ND was independent of the degree of temporal lobe gliosis as assessed by quantitation of glial fibrillary acidic protein-immunoreactive cells. These findings suggest that microdysgenesis may be a significant lesion in temporal lobe epilepsy in terms of post-surgical prognosis.
Insights
Microdysgenesis, a microscopic brain malformation, is linked to better seizure-free outcomes in temporal lobe epilepsy patients. Increased neuronal density in white matter and Layer I are key indicators.
Area of Science:
- Neuroscience
- Neuropathology
- Epilepsy Research
Background:
- Microdysgenesis is a microscopic cortical malformation implicated as a seizure substrate in epilepsy.
- Its role in temporal lobe epilepsy (TLE), particularly its incidence, relationship to mesial temporal lobe sclerosis, and epileptogenesis, remains unclear due to a lack of quantitative diagnostic criteria.
Purpose of the Study:
- To conduct a rigorous quantitative analysis of microdysgenesis components in temporal lobectomy specimens.
- To establish well-defined quantitative pathological diagnostic criteria for microdysgenesis.
- To investigate the relationship between microdysgenesis and post-surgical seizure outcomes in TLE.
Main Methods:
- Utilized three-dimensional cell counting methods on temporal lobectomy specimens.
- Measured white matter, cortical, and Layer I neuronal densities (NDs) via immunohistochemistry.
- Employed neuronal markers: neuronal nuclear antigen and calbindin D-28-K; quantified glial fibrillary acidic protein for gliosis.
Main Results:
- Patients achieving seizure-free outcomes (Class I) exhibited significantly more microdysgenetic features.
- Higher white matter ND (P < 0.05), especially of small neurons (<10 µm diameter) (P < 0.01), was observed.
- Increased Layer I ND (P < 0.05) and higher numbers of Cajal-Retzius-like calbindin-positive neurons (P < 0.05) were noted.
Conclusions:
- Microdysgenesis, characterized by specific neuronal densities, is associated with favorable post-surgical seizure control in TLE.
- White matter neuronal density in microdysgenesis is independent of the degree of temporal lobe gliosis.
- Microdysgenesis represents a significant pathological lesion influencing surgical prognosis in temporal lobe epilepsy.