Effects of chronic alcohol consumption on the broad phospholipid signal inhuman brain: An in vivo P-31 MRS study

Background: Phosphorus magnetic resonance spectroscopy (P-31 MRS) allows fo r the measurement of phospholipids and their breakdown products in the huma n brain. Fairly mobile membrane phospholipids give rise to a broad signal t hat co-resonates with metabolic phosphodiesters. Chronic alcohol exposure i ncreases the rigidity of isolated brain membranes and, thus, may affect the amount and transverse relaxation times (T-2) of MRS-detectable phospholipi ds. We tested the hypothesis that subjects who were heavy drinkers have sti ffer membranes than controls who were light drinkers, as reflected in a sma ller broad signal component and a shorter T-2 of the broad signal in P-31 M R spectra of the brain. Methods: Thirteen alcohol-dependent heavy drinkers (mean age 44 years) were studied by localized P-31 MRS in the centrum semiovale and compared with 1 7 nondependent light drinkers of similar age. The broad component signal wa s separated from the metabolite signal by convolution difference, which is based on the large difference in line widths of these two signals. Longitud inal and T-2 relaxation times were measured using standard methods. Results: The broad component integral was 13% lower in the brain of heavy d rinkers compared with light drinkers (p < 0.001) and remained significantly smaller after corrections for both longitudinal and transverse relaxations (p < 0.01). The T-2 distribution of the broad component consistently showe d two resolvable components in both groups. The fast relaxing component had the same T-2 in both groups (T-2 = 1.9 msec). The slower relaxing componen t T-2 was 0.6 msec shorter in heavy drinkers compared with light drinkers ( p = 0.08). Conclusions: These results, observed in the absence of white matter volume loss, are consistent with biochemical alterations and higher rigidity of wh ite matter phospholipids associated with long-term chronic alcohol abuse. T he observed smaller broad signal component in these relatively young heavy drinkers is a sensitive measure of white matter phospholipid damage.