Perisylvian dysgenesis. Clinical, EEG, MRI and glucose metabolism features in 10 patients

Abstract

We studied 10 patients who had neurological disorders with a MRI-based diagnosis of perisylvian dysgenesis based on the fact that the parasagittal and centrifugal extremity of the sylvian fissure was abnormally mesial. This abnormality was bilateral in seven cases; in the other three patients, the contralateral sylvian fissure appeared either normal (two cases) or enlarged (open operculum). The perisylvian cortex had a polymicrogyric appearance in most patients. Potential aetiopathogenic factors were determined in four patients. In two of them, ischaemia at mid-gestation was ascribed to death of a co-twin in a context of monozygotic twinning. In the other two patients, who were siblings, genetic factors were suspected. Pseudobulbar palsy was found in eight patients and epilepsy in five patients. We used PET with [18F]fluorodeoxyglucose to test the hypothesis that, despite this clinical and MRI heterogeneity, regional cerebral glucose distribution could have common features in these patients. The analysis of PET data was performed by visual inspection in two cases and by using statistical parametric mapping (SPM) in eight patients compared with a control group. Segmented grey matter MRIs of seven out these patients were also analysed using SPM. We found that the abnormal perisylvian cortex had normal grey matter activity in eight patients and in the other two there was a heterogeneous pattern with areas of preserved metabolism and of decreased metabolism. Metabolic changes were also detected outside the polymicrogyric-like cortex; three patients had hypometabolic areas in cortical regions where the MRI appeared normal and had a normal intensity. When polymicrogyria extended into the white matter, this ectopic dysgenetic cortex was associated with a grey matter pattern within the white matter territory, and was detected by SPM as areas of PET hypermetabolism and MRI hyperintensity. In order to detect possible metabolic changes undetected by the individual analyses, the group of patients was compared with the control group. This comparison revealed bilateral hypometabolism in the frontal opercular cortex. We propose that these PET data be considered in light of the presumed cyto-architectonic pattern of perisylvian dysgenesis, i.e. polymicrogyria. In this malformation, two dense cell layers are separated by a necrotic sparse cell layer. We speculate that the amount of synaptic activity preserved in these dense cell layers depends on the importance and timing of the necrotic process; this hypothesis accounts for the large range of metabolic patterns found, from profoundly decreased glucose metabolism to nearly normal activity.

Discordant phenotypes in first cousins with UBE3A frameshift mutation

“…Monozygotic twinning has been associated with a variety of vascular disruptive events [Jung et al, 1984;Patten et al, 1989;Van Bogaert et al, 1998]. The mechanism resulting in the lesions may have been a transient cerebral vascular compromise associated with placenta vascular anastomoses characteristic of monochorionic twinning [Perlman et al, 1995].…”

Neuroimaging fails to identify asymptomatic carriers of familial porencephaly

“…Most cases are sporadic. However, some observations of familial recurrences have been reported, suggesting that genetic factors could be involved [Berg et al, 1983;Airaksinen, 1984;Smit et al, 1984;Zonana et al, 1986;Sensi et al, 1990;Robinson, 1991;Hilburger et al, 1993;Haverkamp et al, 1995;al-Shahwan and Singh, 1995;Andermann and Andermann, 1996;Bonnemann and Meinecke, 1996;Granata et al, 1997;Van Bogaert et al, 1998]. We describe a new family with porencephaly identified in at least three members in two generations, with cerebral imaging performed in some of the unaffected carriers.…”

Combined Positron Emission Tomography and Magnetic Resonance Imaging for the Planning of Stereotactic Brain Biopsies in Children: Experience in 9 Cases

“…More than 10 years later, PET has not become routinely used in neuropediatrics and the literature on this area remains relatively scarce [14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25]. However, PET is still considered an important tool to elucidate the complexity of the developing brain or to evaluate neurodegenerative disorders and cognitive abnormalities [26, 27]. Its greatest clinical utility lies in the field of epilepsy, where it is used in children with intractable partial epilepsy to localize epileptogenic foci for surgical resection [28].…”