This study was conducted to determine the incidence of grey-white matter abnormalities (GWMAs) on magnetic resonance images (MRIs) in patients with hippocampal sclerosis (HS), to assess the inter-observer reliability of this finding, and to establish a possible relationship between GWMA and histopathological findings in the anterior part of the temporal lobe, as well as its other relation to clinical variables. We established a group of 55 patients with histologically proven HS. Three observers independently reviewed the MRIs to assess whether GWMA was present. Substantial independent inter-observer agreement was reached for 44 of the 55 patients (80%) (Fleiss' kappa 0.732; p<0.0001). GWMAs were present in 38% of patients (HS+GWMA). Focal cortical dysplasia (FCD) of type IIIa (ILAE classification) was present in 31% of patients. FCD type IIIa was present in 52.4% with HS+GWMA, and in 17.6% without GWMA (HS-GWMA) (p=0.007). We did not find any statistically significant differences in the postoperative outcomes between HS+GWMA and HS-GWMA. We did not find any statistically significant differences in the presence or absence of GWMA and FCD of the temporal pole in relation to the onset of epilepsy, the duration of epilepsy, or the presence of potential epileptogenic insults. GWMA in the anterior part of temporal lobe in patients with HS is a reliable assessment sign for observers who are experienced in evaluating the MRIs of epilepsy patients. The presence of GWMA is significantly associated with the presence of FCD type IIIa in these patients. The presence or absence of GWMA and FCD type IIIa does not influence the postoperative outcome of HS patients.

Brno Epilepsy Centre 1st Department of Neurology St Anne's University Hospital and Faculty of Medicine Masaryk University Brno Czech Republic

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