Alcohol and the Cerebellum

Alcohol and the Cerebellum Effects on Balance, Motor Coordination, and Cognition EDITH V. SULLIVAN, PH.D., MARGARET J. ROSENBLOOM, M.A., ANJALI DESHMUKH, M.D., JOHN E. DESMOND, PH.D., AND ADOLF PFEFFERBAUM, M.D. Alcoholics often suffer from motor incoordination resulting from alcoholrelated cerebellar damage. However, the effect of cerebellar structural damage on cognitive functioning has not been clearly demonstrated. It is not known if the relationships observed between cerebellar damage and functional impairments persist with abstinence from alcohol. Cell death may cause permanent loss of function, whereas tissue shrinkage without permanent cell loss might represent the potential for recovery. This article examines research on the interrelationship of alcoholrelated abnormalities in cerebellar structure and function. Research such as this may provide knowledge to guide future rehabilitation efforts. KEY WORDS: AODE (alcohol and other drug effects); cerebellum; motor coordination; cognitive process; equilibrium; brain atrophy; AOD impairment In addition to its role in controlling it contains about as many nerve cells (ap ne of the most widely recog movement, the cerebellum may play an proximately 5 billion for each structure) nized signs of acute alcohol important role in the acquisition of motor (Ghez 1991). The cerebellum consists of intoxication is staggering gait. skills and the cognitive processes that con several subdivisions, each controlling or The motor incoordination trol movement (Ito 1993). The cerebellum element of intoxication is routinely as facilitating different behavioral functions. sessed by highway patrol officers when also may help augment cognitive processes The cerebellum includes the left and right they use standard tests of stance imbal originating in the cerebrum (Leiner et al. hemispheres and the vermis (figure 1). O 1993), such as language production ance (otherwise known as gait ataxia) and Unlike the cerebrum, where each hemi eyehand incoordination. (Appollonio et al. 1993; Petersen 1993) and sphere controls the opposite side of the The obvious signs of gait and coordi mental imagery (Ryding et al. 1993). The body, in the cerebellum each hemisphere nation disturbance demonstrated by these role of the cerebellum in cognition is com controls movement on the same side of the simple tests usually resolve once the plex and controversial. body. Thus, damage to the left hemisphere This article reviews current knowledge person has become sober. However, disrupts movement of the left arm or leg, 1 careful study of alcoholics reveals resid on the motor and cognitive processes con whereas damage to the right hemisphere trolled or facilitated by the cerebellum and ual, subtle, persistent deficits in balance disrupts movement of the right limbs. describes damage to the cerebellum associ that may put them at increased risk of The vermis lies between and in front of ated with longterm alcoholism. The article accidents, such as falling. These deficits the cerebellar hemispheres. It has 10 lobules may be related to alcoholinduced patho then explains how researchers are seeking to relate this damage both to problems with and is named for its wormlike appearance. logical changes in the cerebellum, one of Damage to the vermis can result in poor the brain’s main centers of postural con balance and motor coordination and to some of the characteristic cognitive deficits control of posture and upright position, trol and motor coordination. ataxia (widespread stance and unsteady associated with alcoholism. 1 balance), and dysarthria (irregular and The exact definition of the term “alcoholism” varies explosive cadence of speech). The superior with the article cited. Readers are encouraged to (upper) lobules of the vermis are especially consult the original source for the precise definition. TRUCTURE OF THE EREBELLUM S C In general, however, alcoholism may be defined as involved with refinement of coordination abnormal craving for alcohol accompanied by certain The term cerebellum comes from the Latin and postural stability of the legs and trunk. behavioral manifestations including loss of control and means “little brain.” Although it is only The more inferior (lower) lobules support over alcohol consumption. about onetenth the weight of the cerebrum, coordinated movement of the arms. 138 ALCOHOL HEALTH & RESEARCH WORLD Alcohol and the Cerebellum OGNITIVE UNCTIONS cerebrum. These functions include certain ume also declines with age in nonalcoholics. C F OF THE CEREBELLUM aspects of verbal learning (BrackeTolkmitt In contrast to alcohol, which exerts its greatest effect on the anterior superior et al. 1989; Canavan et al. 1994) as well as lobules, normal aging affects mostly the Nerve cells in the cerebellum communicate word production (Petersen et al. 1989), posterior lobules (Raz et al. 1992). Vermal with nerve cells in the cerebrum, brain problemsolving (Kim et al. 1994), and shrinkage appears to be related to daily stem, and spinal cord, including regions planning (Grafman et al. 1992). alcohol consumption but not necessarily to involved in cognitive functions, such as spatial and other sensory perception, age in alcoholics (Karhunen et al. 1994). problemsolving, organization, and plan LCOHOL S FFECTS ON A ’ E ning. Skilled performance of motor tasks CEREBELLAR STRUCTURE involves timing, feedback from visual and LCOHOL S FFECTS ON A ’ E sensory cues, coordination, and learned Cerebellar degeneration is common in CEREBELLAR FUNCTION patterns or dynamics of movement that alcoholics (Torvik and Torp 1986; Victor allow movements to be made quickly, and Laureno 1978). Researchers have Postural and Motor Function smoothly, and relatively effortlessly (Gil looked at cerebellar damage in the brains of The demonstration that increasing doses man et al. 1981). These functions include alcoholics during postmortem examination. of alcohol are associated with increasing both motor and cognitive processes. The The most consistently reported structural severity of an impairment would provide cerebellum also participates in certain damage in the cerebellum of alcoholics is important evidence that the impairment is aspects of motor skill learning (Sanes et tissue volume loss in the anterior superior alcohol related. However, this type of al. 1990), control of reflexive actions (e.g., vermis (Victor et al. 1989). Tissue volume alcohol doseresponse relationship has blinking one’s eye in response to a signal loss in this area is due especially to either been difficult to demonstrate for cerebellar associated with the delivery of a puff of air shrinkage or atrophy of Purkinje cells impairment. In one study (Estrin 1987), to the eye) (McGlinchyBerroth et al. (Charness 1993; Victor et al. 1989; Pentney degree of ataxia was shown not to be as 1994), motor ideation (e.g., the mental 1993), large nerve cells that make up much sociated with total lifetime consumption representation of a movement) (Ryding et of the volume of the vermis. of alcohol; however, degree of eyefoot al. 1993), and tactile learning of complex Structures at the base of the cerebellum incoordination was related to increasing figures (Roland et al. 1989). also may be affected by excessive alcohol alcohol consumption when ataxic alco The cerebellum may contribute to cogni consumption (Allsop and Turner 1966; holics were pooled with nonataxic alco tive functions carried out primarily by the Victor et al. 1989). These regions regulate holics and healthy control subjects. eye movements, particularly when both the Signs of ataxia can wax and wane DITH ULLIVAN H head and the eyes are in motion. Damage to E V. S , P .D., is an associate corresponding with periods of alcoholic professor in the Department of Psychiatry these regions can cause “slippage” of the drinking and abstinence, providing evi visual image (i.e., apparent displacement of and Behavioral Sciences, Stanford Univer dence for specific adverse effects of sity School of Medicine, Stanford, CA, and a visually perceived object) and result in alcohol on motor coordination. Abstinent visual illusions and postural instability, a health science specialist in the Psychiatry alcoholics may show improvement in Service, Veterans Affairs (VA) Palo Alto which may be precursors of falling balance (Allsop and Turner 1966; Diener (Radebaugh et al. 1985). In addition, such Health Care System, Palo Alto, California. et al. 1984; Victor et al. 1989) and periph visual misperception can result in errors of eral nerve functioning, including percep MARGARET J. ROSENBLOOM, M.A., is a eyehand or eyefoot coordination, such as tion of touch and position sense, that is, is needed for safe driving. health science specialist in the Psy the ability to detect the position of the chiatry Service, VA Palo Alto Health Cerebellar volume loss is confirmed by body and its parts (Palliyath and Schwartz neuroimaging techniques that provide Care System. 1993). New research must be conducted quantitative measurement of the different to determine if alcoholrelated imbalance ANJALI DESHMUKH, M.D., is a postdoctor tissue types of the brain. Studies using results from cerebellar pathology or from al fellow in the Psychiatry Service, VA computed tomography and magnetic reso poor functioning of the peripheral nervous 2 nance imaging (MRI) (Haubek and Lee Palo Alto Health Care System. system in the body’s extremities, such as 1979; Hillbom et al. 1986; Kennedy et al. the hands and feet. Peripheral neuropathy OHN ESMOND

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