Distinctive ionic transport of freshly excised human epileptogenic brain tissue

TL;DR

This study reveals that epileptogenic brain lesions exhibit unique frequency-dependent electrical conductivities, with higher saturation frequencies compared to normal tissue, potentially aiding in better identification and understanding of epileptic regions.

Contribution

The paper demonstrates that epileptogenic lesions have distinct electrical conductivity profiles, especially at high frequencies, distinguishing them from normal tissue and tumors.

Findings

Epileptogenic lesions show higher saturation frequencies in conductivity.

Conductivity profiles differ qualitatively between lesions, normal tissue, and tumors.

Frequency-dependent conductivity can potentially aid in identifying epileptogenic tissue.

Abstract

Epileptogenic lesions have higher concentrations of sodium than does normal brain tissue. Such lesions are palpably recognized by a surgeon and then excised in order to eliminate epileptic seizures with their associated abnormal electrical behavior. Here we study the frequency-dependent electrical conductivities of lesion-laden tissues excised from the brains of epilepsy patients. The low-frequency (< 1000 Hz) conductivity of biological tissue primarily probes extracellular solvated sodium-cations traveling parallel to membranes within regions bounded by blockages. This conductivity rises monotonically toward saturation as the frequency surpasses the rate with which diffusing solvated sodium cations encounter blockages. We find that saturation occurs at dramatically higher frequencies in excised brain tissue containing epileptogenic lesions than it does in normal brain tissue. By contrast, such an effect is not reported for tumors embedded in other excised biological tissue. All told, epileptogenic lesions generate frequency-dependent conductivities that differ qualitatively from those of both normal brain tissues and tumors.