*5.4.2 Resective surgery in extra-temporal lobe epilepsy*

Focal lesion, lobar or multilobar resections can be undertaken in the frontal, occipital, and parietal lobes with the expectation of curing or improving seizures. Lesions in eloquent areas of speech, language, and motor function may not be suitable for resection given the postoperative implications of this procedure. In areas adjacent to motor and somatosensory cortex, intraoperative neuro monitoring may be required. The outcomes of non-lesional or MRI-negative resections are less successful [55].

Most patients with extratemporal resections will have invasive electrode recordings because the epileptogenic zone is often not as well defined as in temporal-lobe epilepsy. The outcome for extra temporal-lobe resections is in the region of 60% [52]. Predictors of success include a greater extent of surgical resection, structural pathology on MRI, and concordant structural and electrophysiological imaging. For patients with cortical dysplasia, seizure freedom outcomes are reported to be in the region of 40–70% and are inversely related to the length of follow-up [58]. The best postoperative outcome is associated with type 2B focal cortical dysplasia [58].

#### **Figure 4.**

*Intraoperative functional hemispherectomy view showing the middle cranial fossa after removal of the temporal lobe(a), falx cerebri (fc) and corpus callosum(cc) after removal of the parietal lobe, temporal lobectomy and disconnection of the frontal lobe(f), and occipital lobe(o).*

Frontal lobe resections account for up to 30% of cases and carry a 1-year seizure remission rate of approximately 45% (range 21–61%) and less durable long-term outcomes [59]. The EZ frequently extends beyond MRI-defined lesions, and the resection may need to be tailored according to invasive EEG findings [52]. The best postoperative outcome is associated with type 2B focal cortical dysplasia, a focal seizure onset, and total resection of the EZ.

In insular resection, seizure remission after resection of insular tumor is in the range of 74–84% [60], and insular resection with non-lesional requires a meticulous analysis of the risk–benefit ratio.

Usually parietal seizures are associated with lesional areas; seizure freedom ranges between 45 and 78%, with the best being associated with a focal MRI lesion [61]. Occipital lobe resection seizure freedom averages 65% (range between 52 and 100%) [61]. While occipital lobe epilepsy surgery carries significant risk of postoperative visual dysfunction, seizure freedom is less than that of frontal and parietal lobe.

#### *5.4.3 Functional hemispherectomy*

When the EZ is extensive in one hemisphere, hemispherectomy, or functional hemispherectomy, may be considered. Generally, this is restricted to individuals who have a hemiparesis with loss of meaningful hand function [6]. Seizure freedom occurred in73% of patients. Most patients who are walking prior to surgery remain so afterward, whereas cognitive outcomes are usually stable, with language functions having developed in the contralateral hemisphere (**Figure 4**) [6].
