**6. Palliative treatment**

#### **6.1 Corpus callosotomy**

This is a palliative interhemispheric surgical approach for PR patients, which consists of surgical disconnection of the corpus callosum to disrupt synchronization of epileptiform discharges between both brain hemispheres. It is indicated in multifocal

#### *Recent Advances in Epilepsy Surgery DOI: http://dx.doi.org/10.5772/intechopen.107856*

ictal onset where seizures emanate from bilateral cortical foci at different frequency. Indication could also include failed or poor response with VNS implantation [62].

Concerning the outcome, several studies have suggested that complete corpus callosotomy is more effective, and its efficacy is sustainable with less relapse rates compared with anterior 2/3 corpus callosotomy (88% versus 58% in pediatric patients, [63]. Drop attacks improved from corpus callosotomy more than other generalized seizure types. Transient disconnection syndrome was significantly more likely in total corpus callosotomy than in anterior 2/3 corpus callosotomy [63, 64].

The decision whether to perform anterior 2/3 corpus callosotomy versus complete/ total corpus callosotomy is based on the degree of cognitive impairment and developmental delay and is also guided intraoperatively in some subjects by the presence of EEG activity desynchronization or transformation of generalized epileptiform

#### **Figure 5.**

*Corpus callosotomy; (a); brain MRI, coronal section T1 weighted, showing the disconnection of the corpus callosum (one row), (b); brain MRI sagittal section T2-weighted showing anterior 2/3 of the disconnection of the corpus callosum (2 rows).*

#### **Figure 6.**

*Vagus nerve insertion, a: Vagus nerve dissection, b: Electrode insertion, around the VNS, c: The lead of the device fixed to the muscle, and introduced subcutaneous to the infrascapular area, d: Intraoperative cheek of the stimulator, before subcutaneous insertion.*

discharges to asynchronized (lateralized) epileptiform discharges during the surgical course of the corpus callosotomy procedure (**Figure 5**) [64].

### **6.2 Vagus nerve stimulation**

This is a type of stimulation of the vagus nerve on a set schedule. It is a well-established palliative treatment although it seems that VNS is unlikely to offer a substantial advance in epilepsy surgery. Current evidence points toward a deactivation of the nucleus of the solitary tract with widespread projections to the dorsal raphe nucleus, locus coerules, thalamus, hypothalamus, amygdala, and hippocampus [18]. A metanalysis has demonstrated a 44.1% decrease in seizure frequency with a follow-up of more than 3 years (**Figure 6**) [65].

### **6.3 Responsive neuro-stimulator (RNS)**

RNS is a programmable neurostimulator, which is cranially implanted and connected to one or two depth and/or subdural cortical strip electrodes to detect the onset of seizure and stop it as it occurs. It is now gaining a major position in the USA as a new device with closed-loop system [66]. It is more effective in focal onset seizure, with 75% of seizure reduction [67].
