Scanning the alcoholic brain

Magnetic resonance and spectroscopic imaging of the brain has revealed that abstinence from alcohol may make the brain grow stronger.

Structural brain damage is strongly associated with chronic alcohol abuse. Damage can be straightforward loss of grey matter - the neural cell bodies of the cerebral cortex and the outer layer of the cerebellum as well as loss of white matter - the fibres that extend from neural cell bodies and connect them together throughout the brain. Tissue loss is most widespread in the white matter of the frontal lobes and the cerebellum, which is involved in coordination and regulation of muscle activity. However, researchers suspected that prolonged abstinence from alcohol allows the brain to reverse some of the structural damage caused but evidence was scant.

Radiologist Dieter Meyerhoff and colleagues at the University of California - San Francisco School of Medicine wanted to determine whether abstinence could indeed lead to a reversal of damage to these parts of the brain. They have used quantitative neural imaging based on magnetic resonance and NMR spectroscopy to reveal the effects of prolonged abstinence from alcohol.

Meyerhoff and his team compared two groups of alcoholics (average age 46 years). The first group had previously been treated for alcoholism and had been abstemious for about two years. The second group were individuals who were still heavy drinkers and had never been treated. People in each group were matched for their long-term drinking patterns. No control group was used because this was a comparative study.

MRI and NMR are non-invasive methods that provide a "snapshot" of the structural and metabolic integrity of all regions of the brain and can distinguish between grey and white matter, unlike computer-assisted tomography (CAT) scans. This latter point is crucial in allowing the researchers to discuss the functional significance of alcohol-induced brain damage.

The scans revealed that abstinent alcoholics had more white matter in their frontal lobes than heavy drinkers, but the difference was not seen in other parts of the brain. The more prolonged the abstinence, however, the more white matter the ex-alcoholics had. Specific damage, lesions, were fewer in the abstemious than with the current drinkers in most areas scanned while the volume of grey matter in the abstinent alcoholics was greater in some but not all regions of the frontal lobes. "These results suggest reversal of structural abnormalities in some brain regions of abstinent alcoholics," explains Meyerhoff, "and persistent structural damage in other brain regions. We still need to learn, however, what this means for the individual's brain function."

The study also revealed that the corpus callosum, the large band of fibrous white matter that connects the left and right hemispheres of the brain, is also affected. So too is the anterior aspect of the hippocampus and the mammillary bodies, brain structures that engage in consolidation of new memories.

The simplest sequence consists of a 90 degree RF pulse without any gradients with reception of the signal by the RF coil immediately after the single RF pulse. Many sequences used for imaging can be used for spectroscopy also (such as the spin echo sequence).

The NMR component - known in the medical profession as just MR spectroscopy is performed with a variety of pulse sequences. The difference between an imaging sequence and a spectroscopy sequence is that instead of using the data to provide spatial or positional information, the data help identify different chemical compounds. An MRS scan of the brain can thus provide important metabolic information about the activity of different regions and allow researchers to measure concentrations of the major grey and white matter metabolites N-acetylaspartate (NAA), creatine, and choline using automated spectroscopic processing methods. NAA is a neuronal marker, creatine a marker of energy metabolism and choline indicates membrane products such as phosphocholine, glycerophosphocholine and acetylcholine. However, in a note of caution, the team points out that for their particular approach to the study the MRS data did not uncover chemical differences between the abstainers and the drinkers.

In practical terms the findings from Meyerhoff and his colleagues suggest that the brains of alcoholics can recover from past abuse, to some extent, which should provide encouragement to remain sober.