Microdysgenesis in resected temporal neocortex

Abstract

Fifty patients underwent superficial temporal lobectomy for intractable temporal lobe epilepsy. Total cure rate was 52%, and significant improvement was achieved in 88%. Cytoarchitectural changes in gray and white tissue were analyzed under light microscopy. Neuronal dysgenesis was correlated with the duration of seizure disorder, age of onset, and other etiologic factors, and with clinical outcome. Temporal lobes from 33 neurologically normal autopsy brains which were age- and sex-matched with patients were examined as controls. Severe neuronal ectopia (greater than 8 neurons/2 mm2 white matter) was present in 42% of patients with epilepsy and in none of controls. There was neuronal clustering in 28% of those with epilepsy, and Chaslin's (subpial) gliosis in 38%. Controls did not have these changes. The presence of severe neuronal ectopia and clustering was predictive of a favorable clinical outcome following surgery (p less than 0.05). No correlation was found between microdysgenesis and other factors. These findings suggest that the presence of neuronal dysgenesis may be of significance in the clinical outcome following surgery, and that the abnormal tissue may be important as a morphologic substrate for seizures in some patients.

Early history of subplate and interstitial neurons: from Theodor Meynert (1867) to the discovery of the subplate zone (1974)

“…In the context of temporal lobe epilepsy, interstitial neurons within white matter are usually described as heterotopic (Meencke & Janz, 1984;Hardiman et al 1988;Armstrong, 1993;Wolf & Weistler, 1993;Mischel et al 1995) and thought to represent one element of a group of developmental disorders frequently referred to as cortical dysplasia (Taylor et al 1971), glioneuronal hamartia (Wolf & Weistler, 1993), microdysgenesis (Meencke & Janz, 1984;Hardiman et al 1988;Armstrong, 1993) or heterotopia . Rojiani et al (1996) found that these 'residual ⁄ heterotopic neurons' were significantly more numerous in temporal than in frontal or occipital cortex, and concluded that they represent interstitial remnants of the subplate which have failed to undergo programmed cell death.…”

Temporal Lobe Epilepsy: When Are Invasive Recordings Needed?

“…Focal cortical dysplasia has been reported in 6-20% of patients who undergo temporal resection (106,107). On MRI, the most definite abnormality is the presence of cortical thickening associated with a poor differentiation of the gray-white matter (108,109).…”

Abnormal Network Activity in a Targeted Genetic Model of Human Double Cortex

“…They are often associated with patients having severe epilepsies or cognitive defects (Mischel et al, 1995;Porter et al, 2003). Thus, cortical malformations are present in Ͻ24% of all epilepsy patients but are found in 40% of cases that are refractory to treatment (Hardiman et al, 1988;Farrell et al, 1992). Anatomical and functional studies in rodents with cortical malformations suggest that ectopic neurons form afferent and efferent connections with adjacent cortex (for review, see Chevassus-Au- , indicating that heterotopias are integrated within cortical networks.…”