Effects of Chronic Alcohol Consumption on the Broad Phospholipid Signal in Human Brain: An In Vivo 31P MRS Study.

Background: Phosphorus magnetic resonance spectroscopy (³¹P MRS) allows for the measurement of phospholipids and their breakdown products in the human brain. Fairly mobile membrane phospholipids give rise to a broad signal that co-resonates with metabolic phosphodiesters. Chronic alcohol exposure increases the rigidity of isolated brain membranes and, thus, may affect the amount and transverse relaxation times (T₂) of MRS-detectable phospholipids. We tested the hypothesis that subjects who were heavy drinkers have stiffer membranes than controls who were light drinkers, as reflected in a smaller broad signal component and a shorter T₂ of the broad signal in ³¹P MR spectra of the brain. Methods: Thirteen alcohol-dependent heavy drinkers (mean age 44 years) were studied by localized ³¹P MRS in the centrum semiovale and compared with 17 nondependent light drinkers of similar age. The broad component signal was separated from the metabolite signal by convolution difference, which is based on the large difference in line widths of these two signals. Longitudinal and T₂ relaxation times were measured using standard methods. Results: The broad component integral was 13% lower in the brain of heavy drinkers compared with light drinkers ( p < 0.001) and remained significantly smaller after corrections for both longitudinal and transverse relaxations ( p < 0.01). The T₂ distribution of the broad component consistently showed two resolvable components in both groups. The fast relaxing component had the same T₂ in both groups (T₂= 1.9 msec). The slower relaxing component T₂ 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 white matter phospholipids associated with long-term chronic alcohol abuse. The observed smaller broad signal component in these relatively young heavy drinkers is a sensitive measure of white matter phospholipid damage. [ABSTRACT FROM AUTHOR]