Additional value of Magnetic Resonance Spectroscopy for epilepsy diagnostics in the normal appearing epileptogenic zone

Abstract

Epilepsy affects 50 million people worldwide approximately, thus it is considered one of the most common neurological diseases. For this reason, a reliable diagnosis is of paramount importance. Neuroimaging plays an essential role in the evaluation. Although CT scans are typically the first modality used to detect the underlying cause of an epileptic seizure, they are likely to miss the majority of the epileptogenic lesions. Therefore, other imaging modalities are used to detect the cause of epilepsy. MRI is generally performed; however, it only identifies structural pathology in the epileptic brain in one third of the epileptic patients. For that reason, MRS is a promising tool in the detection of the normal appearing epileptogenic zone. This modality detects abnormalities that are invisible to a conventional MRI because metabolic abnormalities often precede structural changes.

TLE is the most common form of focal epilepsy in which about 20% of patients have negative structural MR images. The majority of the reviewed studies confirm that NAA, Cr and Cho are the most commonly used metabolites to identify the epileptogenic zone in MRI negative TLE and ETLE. Moreover, NAA/Cr, NAA/Cho and NAA/(Cr+Cho) are the most widely accepted ratios for lateralization of the normal appearing epileptogenic zone. Furthermore, NAA and MI have been reported as the metabolites that best enable the study of seizure spread.