32 - Neuroimaging of substance abuse: commentary

Summary

Neuroimaging offers a unique window into brain structure and physiology not otherwise available in living persons. Alcohol and other substances of abuse change the brain, and these changes themselves may contribute to maintenance of the disorders. Thus, it is often hard to know whether the brain alterations observed in patients with alcohol and substance abuse are cause or effect. Their clinical trajectories are classically ones of exacerbations and remissions, with some unfortunate individuals ending in death. With animal models we can manipulate many factors out of experimental control in humans; with humans we are limited to naturalistic observations following the course of the disorder. Yet, with longitudinal observations through remissions and exacerbations, some of the cause and effect mystery can be resolved.

The three preceding chapters set forth reviews of major neuroimaging approaches to the problem – structural integrity with computed tomography (CT) and magnetic resonance imaging (MRI), physiological response to cognitive and motor challenge with functional MRI (fMRI), metabolic and neurotransmitter function with positron emission tomography (PET) and single-photo emission computed tomography (SPECT), and metabolite assays with MR spectroscopy. Each of the approaches has strengths and limitations and they should all be considered complementary to each other. Done well, each requires substantial technical sophistication.

Among the insights we can potentially gain from in-vivo human neuroimaging regarding alcohol and substance abuse disorders are characterization of neuropathology; factors modulating or contributing to the onset, course, and maintenance of misuse; the scope and limits of recovery; and possible benefits of selective substance use (see Box 32.1).