Old Lesions and New Targets: sEEG-Identified Onsets in Traditionally Inoperable Epilepsy Lesions and Associated Surgical Outcomes

Patients with epilepsy who do not respond to pharmacotherapy are often offered a noninvasive diagnostic workup to localize an epileptogenic focus that might be treated with resection, neuromodulation, or ablation. Yet in many cases, this evaluation fails to identify surgical candidates. For example, patients with tuberous sclerosis, periventricular nodular heterotopia, or polymicrogyria may have clearly visible lesions on MRI, but the resulting epileptogenic onset zones/networks are often too complex for scalp electroencephalography to decode. Similarly, seizures arising from the cingulate gyrus originate in deep structures that are inaccessible to noninvasive techniques. In post-traumatic epilepsy without a dominant lesion such as mesial temporal sclerosis, injury is often too diffuse to define a clear seizure-onset zone. Stereoelectroencephalography (sEEG), with its ability to map deep brain networks in detail, offers a unique solution for these challenging cases. In this review, we highlight how sEEG has expanded surgical options and provided hope for seizure freedom in patients once considered medically and surgically untreatable, and we aim to encourage further study into its potential applications.