Clinical applications of MR spectroscopy in epilepsy☆

Proton magnetic resonance spectroscopy (1H MRS) is a noninvasive imaging technique that can easily be added to the conventional magnetic resonance (MR) imaging sequences. Using MRS one can directly compare spectra from pathologic or abnormal tissue and normal tissue. Metabolic changes arising from pathology that can be visualized by MRS may not be apparent from anatomy that can be visualized by conventional MR imaging. In addition, metabolic changes may precede anatomic changes. Thus, MRS is used for diagnostics, to observe disease progression, monitor therapeutic treatments, and to understand the pathogenesis of diseases. MRS may have an important impact on patient management. The purpose of this chapter is to provide practical guidance in the clinical application of MRS of the brain. This chapter provides an overview of MRS-detectable metabolites and their significance. In addition some specific current clinical applications of MRS will be discussed, including brain tumors, inborn errors of metabolism, leukodystrophies, ischemia, epilepsy, and neurodegenerative diseases. The chapter concludes with technical considerations and challenges of clinical MRS.

The purpose of this study was to evaluate the role of magnetic resonance spectroscopy (MRS) in nonlesional temporal lobe epilepsy.

Between April 2011 and December 2013, a total of 30 patients having partial seizures with or without secondary generalization were selected from the Neurology Department, Sayed Galal Hospital, Al Azhar University and were studied in this work. All patients included in the study had clinical history, seizure symptoms, inter-ictal electroencephalography and neuroimaging findings that were consistent with “non-lesional epilepsy of temporal lobe origin”. We mean by non-lesional epilepsy that those cases are not secondary to other pathological lesions e.g. tumor, vascular insult or post inflammatory. Mesial temporal sclerosis was considered as nonlesional temporal lobe epilepsy. Each patient was thoroughly asked about the detailed clinical history after reviewing the referring imaging request and laboratory findings. The MRI and MRS examinations were performed in all the patients in one session. They were performed at 1.5 T super conducting system.

MRS was performed in a total of 30 patients. Sixteen patients were males and 14 were females. The average age of the patients was 32 years (range: 17–47 years). Seventeen patients (56.7% of total patient number) were found to have clinical and EEG criteria of epileptic activity related to temporal lobe origin on the right side, while 11 patients (36.7% of total patient number) were found to have these findings on the left side. Two patients (6.6% of total patients’ number) were having bilateral temporal lobe epileptic activity. Twenty six patients (about 87% of total patient number) were able to be lateralized with MRS using asymmetry index, 16 cases lateralized to the right side (about 53% of total patient number) and 10 cases lateralized to the left side (about 34% of total patient number). The remaining 4 patients (about 13% of total patient number) failed to be lateralized in our study. The sensitivity and specificity of the Conventional MRI and MR spectroscopy for detection of mesial temporal lobe epilepsy were 60% & 65% and 86% & 83% respectively.

MR spectroscopy is a very sensitive guiding tool in predicting the temporal lobe epilepsy (TLE) and the side of involvement in patients with TLE even in patients with MR negative studies. It helps in detecting abnormal spectra of various brain metabolites. MR spectroscopy has demonstrated consistent metabolic abnormalities in partial seizures. MRS can also detect bilateral affection with the ipsilateral side more affected.

Epilepsy affects 65 million people worldwide, a third of whom have seizures that are resistant to anti-epileptic medications. Some of these patients may be amenable to surgical therapy or treatment with implantable devices, but this usually requires delineation of discrete structural or functional lesion(s), which is challenging in a large percentage of these patients.

Advances in neuroimaging and machine learning allow semi-automated detection of malformations of cortical development (MCDs), a common cause of drug resistant epilepsy. A frequently asked question in the field is what techniques currently exist to assist radiologists in identifying these lesions, especially subtle forms of MCDs such as focal cortical dysplasia (FCD) Type I and low grade glial tumors. Below we introduce some of the common lesions encountered in patients with epilepsy and the common imaging findings that radiologists look for in these patients. We then review and discuss the computational techniques introduced over the past 10 years for quantifying and automatically detecting these imaging findings. Due to large variations in the accuracy and implementation of these studies, specific techniques are traditionally used at individual centers, often guided by local expertise, as well as selection bias introduced by the varying prevalence of specific patient populations in different epilepsy centers. We discuss the need for a multi-institutional study that combines features from different imaging modalities as well as computational techniques to definitively assess the utility of specific automated approaches to epilepsy imaging. We conclude that sharing and comparing these different computational techniques through a common data platform provides an opportunity to rigorously test and compare the accuracy of these tools across different patient populations and geographical locations. We propose that these kinds of tools, quantitative imaging analysis methods and open data platforms for aggregating and sharing data and algorithms, can play a vital role in reducing the cost of care, the risks of invasive treatments, and improve overall outcomes for patients with epilepsy.