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Cerebrocortical microdysgenesis in neurologically normal subjects: a histopathologic study
1Dyslexia Neuroanatomical Laboratory, Beth Israel Hospital, Boston, MA 02215.
Abstract:
Previous studies showed that few foci of cerebro-cortical microdysgenesis (molecular layer neuronal ectopias and focal laminar dysplasia) are present in up to 26% of variably processed normal brains; they are more common in the right inferior frontal region. Brains of male developmental dyslexics processed in serial histologic sections showed 30 to 140 foci of these types of anomalies, predominantly in left perisylvian cortex. Here, we present the results of a detailed analysis of ten normal brains also processed in serial sections. The ages ranged from 3.5 to 87 years, all male. Three brains showed abnormalities similar in type to those of the dyslexic, but in far smaller numbers and in different locations: two showed a single cingulate focus--one right, one left; the third brain showed two right supratemporal foci. We conclude that the present form of developmental anomaly is rare in normal brains, and that the findings in the dyslexic brains may be significant.
Insights
Cerebro-cortical microdysgenesis, including neuronal ectopias and focal laminar dysplasia, is rare in normal brains. However, these developmental anomalies were found in higher numbers and different locations in dyslexic brains, suggesting significance.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Neuropathology
Background:
- Previous research indicates cerebro-cortical microdysgenesis is present in some normal brains, often in the right inferior frontal region.
- Developmental dyslexic brains exhibit a significantly higher prevalence of these anomalies, primarily in the left perisylvian cortex.
Purpose of the Study:
- To conduct a detailed analysis of ten normal male brains processed using serial histologic sections.
- To compare the prevalence and location of cerebro-cortical microdysgenesis in normal brains with those previously observed in developmental dyslexic brains.
Main Methods:
- Serial histologic sectioning of ten normal male brains (ages 3.5 to 87 years).
- Detailed analysis and comparison of the type, number, and location of microdysgenesis foci.
Main Results:
- Three out of ten normal brains exhibited microdysgenesis, but with significantly fewer foci and in different locations compared to dyslexic brains.
- Abnormalities in normal brains included single cingulate foci (left and right) and two right supratemporal foci.
Conclusions:
- The specific type of developmental anomaly studied is infrequent in normal brains.
- The higher incidence and distinct localization of these anomalies in dyslexic brains suggest they may be significant indicators of the condition.