The role of clinical in vivo 1H‐MR spectroscopy in the evaluation of epilepsies

Article type: Research Article

Authors: Hammen, T.^; | Stefan, H. | Tomandl, B.

Affiliations: Clinics of Neurology Center Epilepsy, University of Erlangen‐Nürnberg, P.O. Box 3520, D‐91023 Erlangen, Germany | Department of Neuroradiology, Clinics of Neurosurgery University of Erlangen Nürnberg, P.O. Box 3520, D‐91023 Erlangen, Germany

Note: [] Corresponding author. Supported by Wilhelm Sander foundation.

Abstract: 1H‐MRS which is a noninvasive method in detecting various brain metabolites containing N‐acetylaspartat (NAA), cholin (Cho), creatin (Cr) GABA and glutamat has become a diagnostic tool for assessing a number of diseases of the central nervous system particularly including epilepsies and brain tumours. 1H‐MRS plays an increasing role in the evaluation of epilepsies and their treatment schedules today. NAA is accepted as a marker of neuronal/axonal density and viability. It's detailed physiological role is yet unknown. A loss or decrease of NAA is seen in diseases which are associated with loss of neurons or axonal degeneration. GABA, glutamate and glutamin (Glx) probably define the epileptic focus in biochemical terms. 1H‐MRS implies high sensitivity and validity in focus localization in patients with temporal lobe epilepsies (TLE) compared to established methods like video EEG, MR‐volumetry and SPECT. In patients with intractable mesial TLE who were scheduled for surgery NAA/Cr or NAA/Cr + Cho asymmetry indexes of the hippocampal formation were created and compared to healty controls. The results were related to the mentioned already established localization techniques. Most authors which investigated this topic likewise found that 1H‐MRS is highly concordant to EEG and MRI‐Vol findings. Recent studies show that 1H‐MRS besides it's capability to lateralize the epileptic focus is able to distinguish between mesial and lateral TLE. In addition to it's sensitivity in focus lateralization 1H‐MRS contains a predictability concerning the evaluation of postoperative outcome in patients with intractable TLE. Most studies reveal that changes contralateral to the epileptogenic focus or bilateral changes in metabolite spectra of 1H‐MRS are associated with a poor whereas homolateral alterations to the focus reveal a good postoperative seizure outcome. The evaluation of anticonvulsive drugs by 1H‐MRS is the topic of various recent studies in which human brain GABA levels are investigated by 1‐HMRS under the influence of antiepileptic drugs mainly including vigabatrin and topiramat. The effect of antiepileptic drugs and their influence on seizure inhibitoring brain metabolites was investigated and the authors were able to create responder profiles by correlating the mentioned metabolites in a long‐term study. They verified an increase of GABA within the beginning of antiepileptic treatment and an increase of homocarnosine, a GABA metabolite, in long term treatment (2–3 months) in the responder group.

Journal: Spectroscopy, vol. 16, no. 3-4, pp. 297-306, 2002