Brain proton magnetic resonance spectroscopy of alcohol use disorders

Abstract

This chapter critically reviews brain proton magnetic resonance spectroscopy ((1)H MRS) studies performed since 1994 in individuals with alcohol use disorders (AUD). We describe the neurochemicals that can be measured in vivo at the most common magnetic field strengths, summarize our knowledge about their general brain functions, and briefly explain some basic human (1)H MRS methods. Both cross-sectional and longitudinal research of individuals in treatment and of treatment-naïve individuals with AUD are discussed and interpreted on the basis of reported neuropathology. As AUDs are highly comorbid with chronic cigarette smoking and illicit substance abuse, we also summarize reports on their respective influences on regional proton metabolite levels. After reviewing research on neurobiologic correlates of relapse and genetic influences on brain metabolite levels, we finish with suggestions on future directions for (1)H MRS studies in AUDs. The review demonstrates that brain metabolic alterations associated with AUDs as well as their cognitive correlates are not simply a consequence of chronic alcohol consumption. Future MR research of AUDs in general has to be better prepared - and supported - to study clinically complex relationships between personality characteristics, comorbidities, neurogenetics, lifestyle, and living environment, as all these factors critically affect an individual's neurometabolic profile. (1)H MRS is uniquely positioned to tackle these complexities by contributing to a comprehensive biopsychosocial profile of individuals with AUD: it can provide non-invasive biochemical information on select regions of the brain at comparatively low overall cost for the ultimate purpose of informing more efficient treatments of AUDs.

Keywords: alcohol dependence; alcohol use disorders; brain metabolites; comorbidity; magnetic resonance spectroscopy; neuroimaging; nicotine; recovery; relapse; smoking.

Fig. 19.1

Single-volume ¹H magnetic resonance (MR) spectrum (right) obtained from the anterior cingulate cortex (see volume of interest on corresponding MR image, left) at 4 T with a 25-ms echo time. The main spectral resonances are labeled and their peak areas can be quantitated via curve fitting; they are proportional to the absolute concentration of the metabolites from which they originate. NAA, N-acetylaspartate; NAAG, N-acetylaspartyl glutamate; Glu, glutamate; Glx, glutamate + glutamine; GABA, gamma-aminobutyric acid (which is usually quantitated via J-editing from different spectra); Cr, creatine + phosphocreatine; Cho, choline-containing metabolites; mIno, myo-inositol.

Fig. 19.2

Relationships of regional gray matter (GM) and white matter (WM) metabolite concentrations (arbitrary units) with measures of cognitive functioning in treatment-naïve heavy drinkers recruited from the community (here, mI ¼ myo-inositol). NAA, N-acetylaspartate. (Adapted from Meyerhoff et al., 2004.)

Fig. 19.3

Absolute N-acetylaspartate (NAA) concentrations (arbitrary units) averaged over cortical brain regions of the brain reward system (BRS) in non-smoking light/non-drinking controls (nsLD), non-smoking (nsALC) and smoking recovering alcohol-dependent individuals (sALC) at 5 weeks of abstinence from alcohol. (Adapted from Durazzo et al., 2013.)