How Focal Seizures Impair Consciousness: Clinical Features and Network Mechanisms in Temporal Lobe Epilepsy

Abstract

Focal impaired consciousness seizures (FICS) are among the most common seizure types in epilepsy and are a major cause of reduced QOL, occurring predominantly in temporal lobe epilepsy. Although seizure activity often remains confined to a focal temporal lobe network, patients develop widespread impairment of consciousness, indicating dysfunction of distributed brain systems rather than local seizure activity alone. Over the past two decades, converging evidence from human electrophysiological recordings, neuroimaging, and experimental animal models has substantially advanced our understanding of the neural mechanisms underlying this phenomenon. This review summarizes current knowledge of the clinical features and pathophysiology of FICS in temporal lobe epilepsy. We discuss evidence supporting the network inhibition hypothesis, in which seizure activity propagates from the hippocampus to subcortical relay structures that suppress the ascending arousal system, leading to impaired consciousness. We further examine emerging evidence implicating thalamocortical oscillations as a potential mechanism of cortical disconnection and review findings on the bilateral network engagement observed during FICS. By reviewing the substantial progress in defining the circuitry underlying impaired consciousness, we highlight the key questions that remain to be addressed in future research.