Dados do Trabalho

Título

Hippocampal T2 relaxometry heterogeneity in people with hippocampal sclerosis

Introdução

Hippocampal sclerosis (HS) is the most frequent pathology in adults treated surgically for epilepsy. In a subset of cases, identification of the lesion is imprecise, especially when MRI abnormalities are subtle or bilateral. Recently, a novel way of analyzing T2 relaxometry data, using its variance (heterogeneity) across hippocampal voxels instead of the mean hippocampal T2 signal, was shown to be an earlier marker of cognitive impairment in the Alzheimer’s disease continuum than the usual T2 mean. Here, we studied the characteristics of T2 heterogeneity and mean in the hippocampi of patients with left HS, right HS and healthy controls.

Objetivo

(i) To characterize hippocampal T2 signal heterogeneity in patients with temporal lobe epilepsy (TLE) and unilateral HS. (ii) To evaluate the accuracy of this method to identify patients with right and left HS in comparison to T2 mean values.

Método

Patients and controls underwent structural MRI with T2 relaxometry. T2 mean signal and heterogeneity were generated for both hippocampi. Laterality indices (LI) for mean and heterogeneity were calculated by LI = (left – right) / (left + right). ANOVA with post-hoc Bonferroni tests were applied to investigate differences among the three groups. ROC curves of the LI results were produced.

Resultados

In the left hippocampus, T2 mean and heterogeneity were higher in patients with left HS when compared to right HS and controls. In the right hippocampus, T2 mean was higher in the right HS group than in controls, but no difference was found between right and left HS. T2 heterogeneity was not statistically different among the groups in the right hippocampus. Laterality index of T2 mean was different among the three groups, whereas laterality index of T2 heterogeneity was different between right HS and left HS, but not between these and controls. Laterality index of T2 mean correctly segregated left HS and controls with an area under the curve (AUC) of 0.87 (p<0.001), right HS and controls with an AUC of 0.88 (p<0.001), and left HS and right HS with an AUC of 0.97 (p<0.001). Laterality index of T2 heterogeneity segregated left HS from right HS with an AUC of 0.79 (P=0.002), and could not segregate the HS groups from controls.

Conclusão

T2 mean was more accurate than T2 heterogeneity to identify patients with left and right HS.

Palavras-chave

Hippocampal sclerosis, epilepsy surgery, MRI, T2 relaxometry.