Magnetic resonance proton spectroscopy in affective disorders

Magnetic Resonance Proton Spectroscopy (HMRS) is a noninvasive method that allows: the observation of dynamic metabolic fluctuations in central nervous system, differentiation of morphological lesions and monitoring of therapy of some neurological diseases. HMRS may be potentially useful in the research of pathological mechanisms underlying the unipolar (UD) and bipolar affective disorder (BD). However no specific patterns of metabolic abnormalities in UD or BD can be described according to current evidence from HMRS studies. The main reasons are: small size of groups and methodological variety of previous studies. The most often described observation in HMRS studies on UD patients is the elevation of choline level in basal ganglia, prefrontal cortex, hippocampus, gyrus cinguli, correlated with severity of depression. The alterations of choline level in basal ganglia and prefrontal cortex in BD were also described but the data are contradictory. No significant decrease of N-acetylaspartate level was detected in UD or BD. Those data suggest the altered neuronal cell membrane permeability without degenerative processes in affective disorders. Other HMRS studies revealed the lower glutamine, glutamate, GABA and myoinositol levels in frontal and prefrontal cortex in UD patients compared with BD patients. The decrease of GABA level and increase of glutamate and glutamine levels in occipital cortex of UD and BD patients was reveald in few studies. These abnormalities may reflect the imbalance between the excitatory and inhibitory amino-acid neurotransmitter systems in affective disorders. The normalization of levels of most described above metabolites after the successful therapy with antidepressants, mood stabilizers or electroconvulsive therapy was also described.