Integrity of the corpus callosum in patients with benign temporal lobe epilepsy

Abstract

SUMMARYObjective: Corpus callosum (CC) abnormalities are frequently reported in patients with refractory mesial temporal lobe epilepsy (rMTLE). However, whether CC structural alterations are related to the epileptic syndrome itself or to refractoriness is still unknown. Thus, we aimed to compare patterns of CC change in patients with rMTLE and benign MTLE (bMTLE), the latter of which represents a useful resource to better disentangle factors that contribute to refractoriness. Methods: The study group included 79 patients with bMTLE (mean age 43.2 AE 14. 8 years), 61 with rMTLE (mean age 45.2 AE 12.4 years) and 134 healthy volunteers. Structural magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) were performed to measure thickness, mean diffusivity (MD), and fractional anisotropy (FA) over 50 regions of interest along the cross-sectional CC profile. Statistical analysis comprised analysis of variance (ANOVA) followed by post hoc Tukey's Honest Significant Difference test. Results: We found that all imaging metrics of the CC splenium were altered in rMTLE patients compared to bMTLE and controls. We also found significantly reduced thickness and FA of the anterior CC in rMTLE compared to controls and that FA was reduced only in rMTLE compared to bMTLE. Patients with bMTLE did not differ from controls. Differences between disease subgroups were found in the midbody composed of sensorimotor fibers. Significance: We found altered multimodal imaging metrics of the CC in rMTLE but not in bMTLE. These findings were independent of the radiologic presence of hippocampal sclerosis, suggesting that differences in the distribution of such alterations might be related to refractoriness.

Late drug‐resistance in mild MTLE: Can it be influenced by preexisting white matter alterations?

“…In TLE patients, these tracts have been hypothesized as having a role in the lateralization of seizures and in the differences in patients with left and right TLE 34 . In agreement with these results, our DTI analysis at follow‐up confirmed the microstructural involvement of the superior longitudinal fasciculus in rMTLE patients, along with the corpus callosum, which was also shown to be preserved in mMTLE patients but not in rMTLE 5 …”

“…Recent advanced neuroimaging studies have suggested that, regardless of the presence and side of Hs, white matter is relatively spared in mMTLE compared to refractory MTLE (rMTLE) 4,5 . However, whether these structural abnormalities may reflect an initial insult, subsequent epileptogenesis, progressive neurodegeneration, or a combination of causes—including recurrent seizures, early seizure onset, and effects of antiepileptic drugs (AEDs)—remains an unanswered question.…”

Functional Connectivity of the Corpus Callosum in Epilepsy Patients with Secondarily Generalized Seizures

“…Caligiuri et al investigated the CC integrity in patients with benign TLE. They found significantly reduced thickness and FA of the anterior CC in right mTLE ( 20 ). Whelan and his colleagues used TBSS to identify significant FA reduction in the anterior CC from 25 patients with sporadic MRI-negative mTLE ( 21 ).…”

Tract‐specific atrophy in focal epilepsy: Disease, genetics, or seizures?

“…Neither patient-reported seizure frequency nor disease duration showed a significant correlation at these tracts in our analysis, although a correlation with epilepsy duration has been found at the corpus callosum by some diffusion studies. 39,42 Furthermore, greater change at the corpus callosum has been found with refractory versus benign epilepsy, 43 in association with bilateral temporal interictal epileptiform discharges, 44 as well as in an experimental rat model of focal epilepsy where no antiepileptic medications were used. 45 Thus, our interpretation is that atrophy in these tracts is likely to be a consequence of factors that have a bilateral and symmetrical impact, with generalized seizures, antiepileptic medications, and other global factors such as psychological and socioeconomic status all being possible causes.…”