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Published on: August 5, 2014
Histopathology of 3 Tesla MRI-negative temporal lobe epilepsies
Evangelos Kogias1, Dirk-Matthias Altenmüller2, Jan-Helge Klingler1
1Department of Neurosurgery, Medical Center- University of Freiburg, Germany.
Introduction:
Histopathology of MRI-negative temporal lobe epilepsies (TLE) shows heterogeneous findings. The use of either 1.5 or 3 Tesla MRI for the selection of MRI-negative cases and use of older classification systems instead of the current ILAE classification system may account for this heterogeneity. We focus on histopathology of 3 Tesla MRI-negative TLE according to ILAE criteria and investigate potential correlation to seizure outcome 1 year postoperatively.
Materials And Methods:
Twenty specimens (9 neocortical, 11 hippocampal) from eleven 3 Tesla MRI-negative patients with TLE were examined in two steps. Standard stains and immunohistochemical reactions as well as Palmini and Wyler criteria were used prospectively during the initial examination. Retrospectively, all specimens were re-examined and re-evaluated. Phospho-6 and calretinin stains and the ILAE criteria were used during the review examination.
Results:
Initial examination revealed 7 focal cortical dysplasias (FCDs) Palmini type 1, two cases of cortical gliosis, 4 cases of hippocampal sclerosis (HS) Wyler grade 1 and seven cases of hippocampal gliosis. The review examination according to ILAE criteria revealed 4 FCDs type I and 5 mild malformations of cortical development. All hippocampal specimens showed "no HS/gliosis only" after the review examination. Histopathology showed no correlation to seizure outcome.
Discussion:
This is the first histopathological study to include only 3 Tesla MRI-negative cases. The use of ILAE criteria lead to the diagnosis of "no HS/gliosis only" of all hippocampal specimens, a finding not in line with previously reported series. The spectrum of diagnoses within neocortical specimens showed accordingly more mild findings.
Insights
Histopathology in MRI-negative temporal lobe epilepsy (TLE) is re-evaluated using ILAE criteria. Applying these criteria to 3 Tesla MRI-negative TLE cases revealed milder neocortical findings and no hippocampal sclerosis, with no correlation to seizure outcomes.
Area of Science:
- Neurology
- Pathology
- Epilepsy Research
Background:
- Histopathology in MRI-negative temporal lobe epilepsy (TLE) presents heterogeneous findings, potentially due to varying MRI strengths and classification systems.
- This study focuses on the histopathology of TLE cases negative on 3 Tesla MRI, using current International League Against Epilepsy (ILAE) criteria.
Purpose of the Study:
- To investigate the histopathological findings in 3 Tesla MRI-negative TLE cases.
- To evaluate the correlation between histopathology and seizure outcome one year after surgery.
Main Methods:
- Examined 20 specimens (9 neocortical, 11 hippocampal) from 11 patients with 3 Tesla MRI-negative TLE.
- Utilized standard stains, immunohistochemistry, and both older (Palmini, Wyler) and current ILAE classification criteria for prospective and retrospective analysis.
Main Results:
- Initial review showed focal cortical dysplasias (FCDs), cortical gliosis, and hippocampal sclerosis (HS).
- Re-evaluation using ILAE criteria identified 4 FCD type I and 5 mild malformations of cortical development in neocortical specimens.
- All hippocampal specimens were classified as 'no HS/gliosis only' upon review.
- Histopathological findings did not correlate with seizure outcome at 1 year.
Conclusions:
- This is the first histopathological study exclusively on 3 Tesla MRI-negative TLE cases.
- The application of ILAE criteria reclassified all hippocampal specimens as 'no HS/gliosis only', differing from previous reports.
- Neocortical specimens exhibited a spectrum of milder developmental abnormalities.
