Insights from the field of Forel surgery in the era of epileptogenic network models

Epilepsy is increasingly understood as a disorder of large-scale neural networks rather than isolated cortical foci, and this conceptual shift has renewed interest in subcortical structures as therapeutic targets. The field of Forel, a densely packed subthalamic region traversed by the pallido-thalamic tract (PTT) and other major fiber pathways, was historically targeted by the Jinnai–Mukawa group for drug-resistant epilepsy (DRE) when focal resection was not feasible. Although early Forel-H-tomy yielded favorable seizure reduction in selected patients, outcomes varied widely and permanent neurological complications were not uncommon, limiting its broader adoption. With the modern recognition of the epileptogenic network model, classical lesion targets can now be reinterpreted within the framework of basal ganglia–thalamo–cortical circuit dynamics. Some evidence from physiological, imaging, and lesion-network studies suggests a possible role for subcortical structures—including the PTT, subthalamic nucleus (STN), and zona incerta (ZI)— in the modulation of seizure propagation, potentially through influences on thalamo-cortical excitability. Meanwhile, advances in stereotactic technology, from MRI-based targeting to MR-guided focused ultrasound surgery (MRgFUS), have significantly improved the precision and safety of interventions within the subthalamic region. In parallel, deep brain stimulation (DBS) has become an established therapy for DRE, most notably through stimulation of the anterior or centromedian nuclei of the thalamus, and emerging studies suggest potential seizure-suppressive effects from DBS of the subthalamic area. Unlike irreversible lesioning, DBS offers adjustability, reversibility, and network-level modulation through both acute desynchronization and long-term neuroplastic mechanisms. By integrating historical experiences with contemporary neuroanatomical and neurophysiological insights, this review reexamines the field of Forel surgery and considers its possible implications for future neuromodulation strategies. A refined understanding of this subthalamic hub may guide the development of optimized stimulation targets for network-level seizure control.