Thalamo-cortical network dysfunction in temporal lobe epilepsy

Abstract

Objectives: Imaging and neurophysiological data shows that the cortical disfunction caused by focal epilepsy is not limited to the epileptic focus, thus raising the modern vision of focal epilepsy as a network disorder. The involvement of deep thalamo-cortical projections in temporal lobe epilepsy is a clear example. We aimed at demonstrating the interictal functional impairment of thalamo-cortical network in drug-naïve TLE patients through the study of high frequency oscillations of somatosensory evoked potentials (HF-SEP).

Methods: Twelve healthy controls (HC; 8 females, 52.2 ± 17.3 years-old) and 12 drug-naïve TLE patients (8 females, 55.5 ± 21.5 years-old) underwent bilateral median HF-SEP, recorded by scalp electrodes. Cp3'-Fz and Cp4'-Fz traces were filtered (400-800 Hz) to evidence HF-SEP.

Results: HF-SEP duration in the affected hemisphere was significantly longer when compared to that of both the unaffected hemisphere and HC hemispheres. No significant inter-hemispheric differences were found in areas, powers and latencies of HF-SEP wavelets.

Conclusion: Our results demonstrate that TLE induces early interictal functional impairments of the thalamo-cortical network.

Significance: Our data strongly corroborates the vision of focal epilepsy as a network disorder and offers a new neurophysiological tool to test pharmacological, surgical and neuromodulatory therapies.

Keywords: Cortical oscillations; Epilepsy; High frequency oscillations; SEP; Temporal lobe epilepsy.