When should corpus callosotomy be offered as palliative therapy?

Intelligence quotient (IQ) as a predictor of epilepsy surgery outcome

INTRODUCTION

About one-third of patients with epilepsy have a refractory form which is associated with important economic and psychosocial burden. Most of these patients also suffer from comorbidities. One of the most frequent is cognitive impairment. Resective surgery or neuromodulation techniques may improve seizure control. Several factors have been proposed as potential predictors of the success of surgery regarding seizure frequency. We aimed to study preoperative cognitive performance as a predictor of the epilepsy surgery outcome.

METHODS

In this ambispective study we studied total intelligence quotients (IQ) measured before surgery with the Wechsler Adult Intelligence Scale (WAIS) as a potential predictor of Engel Class at 1 year after surgery. Then we included IQ in a multivariate model and tested its performance.

RESULTS

Preoperative IQ was a significant and independent predictor of the Engel Class at 1 year after surgery (OR 0.94; CI 0.90-0.98; p = 0.007). The multivariate model including the age at epilepsy onset, education level, sex, and the type of surgery (resective versus palliative surgery) showed an area under the ROC curve of 0.85.

CONCLUSIONS

A low intelligence level may constitute a marker of worse prognosis after epilepsy surgery. However, other predictors should also be considered when evaluating surgical candidates.

Morphometric Analysis of the Corpus Callosum Using Cadaveric Brain: An Anatomical Study

Purpose:

The present study was conducted to measure the longitudinal and vertical lengths of the brain hemisphere, longitudinal length of the corpus callosum (CC), and distances of CC from the frontal and occipital poles, in order to define its topographic location within the brain hemispheres.

Materials and Methods:

Fifty formalin-fixed human brains were dissected in the midsagittal plane. The parameters measured were as follows: (i) straight distance between frontal and occipital pole (AB); (ii) vertical distance (height) between the upper and lower surface of the brain hemisphere (CD); (iii) frontal pole to anterior-most point of CC (EG); (iv) occipital pole to posterior-most point of CC (ZO); (v) anterior-most point to posterior-most point of CC (EZ); and (v) anterior edge of genu to the upper end of lamina terminalis (EF).

Results:

The mean value of AB, CD, EG, ZO, EZ, and EF was 15.47 ± 0.94 cm, 9.48 ± 0.83 cm, 3.31 ± 0.29 cm, 5.65 ± 0.54 cm, 6.96 ± 0.55 cm, and 2.1 ± 0.39 cm, respectively. AB had the strongest positive correlation with ZO (0.79), whereas CD (height) had it with EZ (0.59). Both AB and CD had a strong positive correlation with EZ. The ratios EZ/AB = 0.45 (P = 0.001) and EZ/CD = 0.73 (P = 0.003) illustrated a steady and significant proportions, present in all the brains studied. Although the mean values of all the parameters were greater in males than in females, only two parameters (ZO and EZ) showed statistically significant (P < 0.05) gender differences.

Conclusion:

The precise anatomical knowledge regarding the morphometry of CC will provide baseline data for the diagnosis and progression of disease affecting it.

Electroencephalography Network Effects of Corpus Callosotomy in Patients with Lennox-Gastaut Syndrome

OBJECTIVES

This study aimed to investigate the functional network effects of corpus callosotomy (CC), a well-recognized palliative surgical therapy for patients with Lennox-Gastaut syndrome (LGS). Specifically, we sought to gain insight into the effects of CC on LGS remission, based on brain networks in LGS by calculating network metrics and evaluating by network measures before and after surgery.

METHODS

Electroencephalographic recordings made during preoperative and 3-month postoperative states in 14 patients with LGS who had undergone successful CC were retrospectively analyzed. First, undirected correlation matrices were constituted for the mathematical expression of functional networks. Then, we plotted these networks to analyze the effects of CC on connectivity. In addition, conventional local and global network measures were applied to evaluate differences in network topology between preoperative and postoperative states.

RESULTS

In the preoperative state, hubs were mainly distributed around the paramedian regions. After CC, the hubs moved from the paramedian regions to the dual-hemisphere and even the lateral regions. Thus, the general connectivity state became more homogeneous, which was verified by network plots and statistical analysis of local measures. The results of global network measures indicated a decreased clustering coefficient in the delta band, decreased characteristic path length in both the delta and gamma bands, and increased global efficiency in the gamma band.

CONCLUSION

Our results showed a consistent variation in the global brain network that converted to a small-world topology with an optimal balance of functional integration and segregation of the network. Such changes were positively correlated with satisfactory surgery results, which could be interpreted as being indicative of LGS recovery process after CC. For patients with refractory LGS along with no focal epileptogenic zone findings, which were not suitable for the resective surgical therapy, our results verified that CC could work as an effective surgical treatment option.

Anterior corpus callosotomy in multistep invasive monitoring and surgery for atonic seizures

Identifying the epileptogenic zone (EZ) in patients with refractory nonlesional frontal lobe epilepsy is frequently challenging. Intracranial EEG (icEEG) recordings are often required to better delineate the EZ, but the presence of an extensive network of connections allowing rapid ictal spread may result in bilateral homologous regional (or extremely diffuse) electrical ictal patterns. Here, we report a case where callosotomy performed after a first nonlateralizing icEEG study allowed for adequate identification of the EZ. The patient, an 18-year-old left-handed woman with daily atonic spells, had synchronous interictal and ictal epileptic activity from both supplementary motor areas (SMAs) during icEEG. Anterior partial callosotomy localized the EZ to the right SMA, as seizures were no longer associated with mirror-image ictal activity over the left SMA. Right SMA resection led to seizure freedom (follow-up of 23 months). This case exemplifies how a partial callosotomy followed by further icEEG recordings may adequately localize the EZ when initial icEEG recordings reveal bilateral synchronous focal or regional ictal activities.

Increased interhemispheric resting-state in idiopathic generalized epilepsy with generalized tonic-clonic seizures: a resting-state fMRI study

PURPOSE

The aim is to examine the resting state functional connectivity (RSFC) between the two hemispheres and its relationships with clinical characteristic in idiopathic generalized epilepsy with generalized tonic-clonic seizures only (IGE-GTCS) patients using a technique called "voxel-mirrored homotopic connectivity (VMHC)".

METHODS

The resting-state functional MRI (Rs-fMRI) was used to measure the RSFC in patients with IGE-GTC and age-gender matched healthy subjects. The between-group difference in interhemispheric RSFC was examined after the interhemispheric RSFC map was obtained by an automated VMHC approach.

RESULTS

Compared to the controls, the IGE-GTCS patients showed significant increases in VMHC in the bilateral anterior cingulate and medial prefrontal gyrus. No areas showed decreased VMHC in patients. Moreover, the VMHC in bilateral thalamus, orbital frontal cortex as well as cerebellum showed significant negative correlations with the illness duration.

CONCLUSIONS

The current findings provide preliminary evidence of increased interhemispheric RSFC in patients with IGE-GTCS during the interictal period. These VMHC deficits in these regions and the inverse relations between VMHC and clinical characteristic may play an important role in the pathophysiology of IGE-GTCS. Our study may contribute to the understanding of neuro-pathophysiological mechanism of epilepsy and psychosocial function impairments in patients with IGE-GTCS.