Magnetic resonance spectrometry (MRS) is now a routine investigation method in neurology. In some situations, its diagnostic sensitivity is better than MRI. In this review, we propose a critical analysis of the large body of literature on brain MRS concerning a wide range of pathologies and many different protocols. The diagnostic value of MRS is not fully determined in all neurological diseases, but the specific properties of MRS (detection of neuron-specific and glial-specific metabolites, quantitative data, reversibility of metabolic lesions) make it a high-performance tool for quantifying neuron, glial and membrane abnormalities. After reviewing the methodological advances in MRS and discussing restrictions on interpretation of spectral data, we describe variations in metabolic patterns detected by MRS in different groups of diseases. The currently reasonable indications for MRS exploration are presented as well as new avenues for research. Based on MRS data, we propose a metabolic definition of encephalopathy which could be useful in better understanding the role of MRS in modern neurology.