PROTON MAGNETIC-RESONANCE SPECTROSCOPY (MRS) IN EPILEPSY

For H-1 magnetic resonance spectroscopy (MRS) studies in epilepsy in v ivo, the main signals of interest have been those from N-acetyl aspart ate (NAA), creatine + phosphocreatine (Cr), choline-containing compoun ds (Cho), and lactate (Lac). Several lines of evidence have indicated that NAA is located primarily within neurons. A reduction of the NAA s ignal is frequently interpreted, therefore, as reflecting loss or dysf unction of neurons. Such a reduction in NAA has been found in practice in many cases where neuronal loss would be expected clinically, and s uch abnormalities have been shown to be present in patients with intra ctable focal epilepsy. The acquisition of spectroscopic data in vivo i s of limited use unless the spatial origin of the signals obtained is known. It is necessary, therefore, to limit the extent of the volume f rom which signal is acquired and to relate this volume to the anatomy of the region under investigation. For this reason, number of common s patial localisation techniques are outlined, and their consequences de scribed. In vivo MRS studies in epilepsy to date have been directed la rgely at the temporal lobes of patients with intractable epilepsy in w hom surgical treatment is under consideration. Results are presented f rom a number of institutions which demonstrate that H-1 MRS can contri bute to the lateralization of the epileptic focus and to the identific ation of bilateral pathology. In providing information both on static metabolic abnormalities, primarily through the NAA signal, and on dyna mic changes associated with seizure activity via the lactate signal, M RS offers the possibility of obtaining information on cerebral metabol ism that is likely to have significant consequences for the management of patients with epilepsy.