Abstract
The increasingly widespread use of stereo-EEG in the pre-surgical evaluation has led to greater recognition of the insula as both a source and surgical target for drug-resistant epilepsy. Clinicians have long appreciated the challenges of diagnosing and treating seizures arising from the insula. Insular-onset seizures present with a wide variety of semiologies due to its dense and complex integration with other brain structures, resulting in the insula's reputation as the "great mimicker." Surgical access to the insula is guarded by the overlying frontal, temporal, and parietal opercula and requires careful negotiation of the Sylvian fissure, the vascular candelabra of the middle cerebral artery, and protection of crucial white matter structures (e.g., corona radiata). Despite these difficulties, open surgical intervention for insular epilepsy is associated with favorable seizure control rates, surpassing those achieved with less-invasive alternatives (e.g., laser ablation). Technical nuances that minimize the risk of adverse functional outcomes following open insular resection (especially hemiparesis) are of tremendous value to the epilepsy surgeon. Here, we review the literature on hemiparesis secondary to insular resection and detail strategies for achieving safe and thorough resection of the insula, with emphasis placed on the posterior insula. We supplement this review with four illustrative cases in which focal, drug-resistant epilepsy was managed via open insular resection with no resultant permanent hemiparesis. Technical insights accumulated through these cases are highlighted.