"Uncomplicated" alcoholism refers to the disease that affects a majority of alcoholics who do not demonstrate clinical symptoms of alcoholism-related disorders such as cirrhosis, dementia, or amnesia. However, rigorous neuropsychological examination has revealed that this population may indeed have cognitive and motor deficits that range in severity from mild to moderate. A study in the May issue of Alcoholism: Clinical & Experimental Research examines the cerebellar functional integrity of patients with uncomplicated alcoholism, finding that the quality and regularity of their movement is disrupted.
"We use the term 'uncomplicated alcoholism' to refer to individuals who meet diagnostic criteria for alcohol dependence but are apparently free of medical, cognitive, or motor abnormalities that can accompany alcoholism," said Edith Sullivan, associate professor of psychiatry at Stanford University School of Medicine and the study's lead author. "These abnormalities include Korsakoff's syndrome or alcoholic cerebellar degeneration, and are marked by clinically detectable behavioral deficits, for example, compromised ability to remember new information or to maintain postural stability."
Sullivan noted that previous research has found that excessive, chronic alcohol consumption can result in damage to cerebellar cellular structure, shown by postmortem examinations, as well as shrinkage of regional cerebellar volumes, shown by in vivo (living) magnetic resonance imaging (MRI) studies.
"Certain regions of the cerebellum that are damaged by chronic alcoholism are important for regulating smooth movement of the arms and legs," said Sullivan. "Selective damage of these structures can cause jerky and somewhat dyscoordinated movement. Thus, even when an alcoholic becomes sober, 'ataxia of movement' or instability and compromised movement fluidity can ensue."
Despite awareness of motor abnormalities in alcoholics, said Peter R. Martin, professor of psychiatry and pharmacology, and director of the Vanderbilt Addiction Center at the Vanderbilt University School of Medicine, "there's a real paucity of information on motor dysfunction in alcoholism. The vast majority of neuropsychological literature on alcohol-induced or alcoholism-associated neuropsychiatric deficits has focused on the more cognitive aspects of higher brain functioning such as memory, reasoning and visuospatial functions. There are a number of reasons why motor dysfunction has not been so much of a focus. One reason is that neuropsychologists have more of an interest in cognitive functions. Accordingly, they have developed some very good standardized neuropsychological assessment batteries that people have used for a long time to study various clinical groups of patients, and which tend to focus on these cognitive aspects of brain functioning. So it is of great interest that this study so carefully analyzes motor functioning in alcoholics."
Researchers examined two groups: 39 abstinent alcoholics (13 men, 26 women) recruited from local inpatient and outpatient treatment facilities, and 21 healthy, age-matched control subjects (9 men, 12 women) recruited from the local community. Participants were given five types of tasks previously shown to be sensitive and specific to selective lesions of the cerebellar hemispheres. These five measures were limb ataxia (alternated finger tapping and variants of the finger-to-nose and heel-to-shin tests), paced tapping, eye-hand coordinated tracing, timed response reflecting preparation and execution time, and postural stability.
"We observed that alcoholic men used rather slow movements in order to follow, with little deviation, an ideal path," said Sullivan. "By and large, alcoholic women were not impaired on these tests, although the accuracy achieved for the speed they moved was not quite up to the par of the control women. Alcoholics were also impaired in gait and postural stability, which could put such individuals at risk of falling." Sullivan and her colleagues additionally found an "altered speed/accuracy trade-off," meaning that the alcoholics seemed to be more deliberate in their movements.
"When they try to move too fast," said Sullivan, "which may actually be 'normal speed' had they not been alcoholics, their movements are jerky and they are unstable. Thus, even when sober, they could look 'drunk.' It would seem reasonable to speculate that the slowing of movement speed to achieve smooth movements is quite adaptive for those who are trying to avoid social embarrassment or a 'run-in' with law enforcers. Although the alcoholic women did not show the same level of impairment as did the alcoholic men, the women showed some evidence for postural instability and for an abnormally small speed/accuracy trade-off in limb movements."
Martin said it's likely that women are actually much more sensitive to brain damage associated with drinking. "It is difficult to match men and women for alcohol exposure," he said, "as men typically drink greater amounts. At the very least, comparisons of alcohol consumption in men and women need to be adjusted for differences in weight. The differences in consumption between the men and women in this study were significant. The men had almost a three-fold higher consumption level than women." He suggested that future research include women who were more closely matched with the men in terms of their alcohol consumption.
Another potential area of future research, said Martin, is whether or not the subtle neurological abnormalities that many alcoholics have are a consequence of alcoholism or were present before they ever started drinking. "Undeniably," he said, "there are some motor and cognitive functions that you see in an alcoholic that, when they stop drinking, do improve with abstinence. But not all abnormalities improve with abstinence. This is the sort of question that we're never going to be able to answer unless we do longitudinal studies, whereby we look at individuals before they ever drink alcohol and then follow alcohol's effects on their functions."
Sullivan added that alcoholics need to be realistic about the effects of chronic alcohol abuse on their abilities. "The identification of performance deficits in sober alcoholics can be important to the individual," she said, "who may otherwise believe that with sobriety, there is performance recovery after a brief abstinence. Unfortunately, this is not always the case."
Funding for this Addiction Science Made Easy project is provided by the Addiction Technology Transfer Center National Office, under the cooperative agreement from the Center for Substance Abuse Treatment of SAMHSA.
Articles were written based on the following published research:
Sullivan, E.V., Desmond, J.E., Lim, K.O., & Pfefferbaum, A.(2002, May). Speed and efficiency but not accuracy of timing deficits of limb movements in alcoholic men and women. Alcoholism: Clinical & Experimental Research, 26(5), 703-713.
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