Temporal lobe developmental malformations and epilepsy

Abstract

Temporal lobe developmental malformations (TLDM) with focal cortical dysplasia and balloon cells may coexist with mesial temporal sclerosis. The true incidence of this dual pathology is unknown. Our aim was to assess the frequency of amygdala (AM)-hippocampal abnormality in a homogeneous population with this specific developmental malformation. MRI-based volumetry of the AM and hippocampal formation (HF) in 30 patients with unilateral TLDM and intractable partial epilepsy was performed. A volume normalization process defined a normal range of HF and AM volumes in control subjects, and enabled the detection of bilateral volume loss. Normalized volumes detected HF atrophy in 26 patients (nine unilateral and 17 bilateral) and AM atrophy in 18 patients (three unilateral and 15 bilateral). Visual analysis detected unilateral HF abnormality in 21 patients and bilateral abnormality in two. When compared with a group of patients with temporal lobe epilepsy and pure hippocampal sclerosis (N = 92), where volumetry revealed bilateral HF atrophy in 18%, a significant difference in the frequency of bilateral HF atrophy was found (p < 0.0001). Dual pathology is frequent in patients with TLDM (87%), and the AM-HF abnormality is often bilateral (57%). Our data suggest that more widespread and potentially epileptogenic lesions coexist with visibly detectable unilateral TLDM. This has implications for the selection of patients for temporal lobe surgery and may influence surgical strategies.

3.0 T MRI of 2000 consecutive patients with localisation-related epilepsy

“…It is more likely to be of benefit in those patients with refractory epilepsy where surgery is being considered as a treatment option. Relaxometry and quantitative analysis can also be used to assess for bilateral MTS, although the rate detected in this series of 4.7% is lower than that reported elsewhere [24]. This suggests it is under-reported and this may have implications in the decision making process for surgical resection as there is likely to be an increased relapse rate in those with bilateral MTS [25].…”

Magnetic Resonance Spectroscopy and Histopathological Findings in Temporal Lobe Epilepsy

“…The generally observed poor outcome of surgery for CMs gave rise to the assumption that these developmental alterations represent epileptic tissue that could be widely spread over the whole temporal lobe or even remote brain regions. This assumption was supported by Ho et al (24), who demonstrated a higher incidence of bilateral hippocampus and amygdala atrophy in patients with MRI-detectable temporal lobe abnormalities. It is not yet known whether a coexisting HS and MRI-negative but microscopically visible CM can be detected with MR spectroscopy, or if differences between HS, DP, and isolated CMs can be detected via the analysis of mesiotemporal chemical spectra.…”

Hippocampal Abnormalities in an MR Imaging Series of Patients with Tuberous Sclerosis

“…This is consistent with the presence of cortical tubers. 25 The association of mechanisms such as repeated stimuli in a vulnerable region may produce irreversible tissue damage, resulting in MTS. We argue that MTS is acquired and is not part of the inherited syndrome.…”