Dose-related effects of alcohol on dynamic posturography and oculomotor measures

Disturbed sensory physiology underlies poor balance and disrupts activities of daily living in alcohol use disorder

Postural stability is a multi-factorial skill maintained implicitly. Components of quiet standing can decline with Alcohol Use Disorder (AUD), cause instability, and disrupt activities of daily living (ADL). To examine how stability factors contribute to ADL and balance, 638 force platform testing sessions measured sway paths acquired during quiet standing in 151 AUD and 96 control men and women, age 25-75. Structural equation (seq) path analysis estimated contributions from age, diagnosis, and sensory perception to sway and measures of ADL and roadside ataxia testing. Whether eyes were open or closed, older AUD and control participants had longer sway paths than younger ones; older men had longer sway paths than older women. Although each sensory ability tested declined with aging, different factor constellations influenced ADL, ataxia scores, or sway path. Seq-path analysis indicated that ADL was strongly dependent on sensory (but not cognitive) systems with sway-path length accounting for upwards of 25% of variance. Within the AUD group, an index of historically-experienced withdrawal symptoms was a common predictor of stability regardless of vision condition. The greatest variance measured by the seq-path model was for predicting platform sway and simple ataxia testing of one-leg standing even though these measures were affected by different predictor variables: strong predictors of one-leg standing were diagnosis and age (R²  = 39.6%-43.2%), whereas strong predictors of sway-path length were sensory factors and withdrawal index (R²  = 22.0%-22.9%). These findings present evidence for appreciating selective factors that contribute to declining postural stability and to liability for compromised quality of life in AUD.

The effect of alcohol on cervical and ocular vestibular evoked myogenic potentials in healthy volunteers

OBJECTIVE

We investigated the effect of alcohol on the cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs). As alcohol produces gaze-evoked nystagmus (GEN), we also tested the effect of nystagmus independent of alcohol by recording oVEMPs during optokinetic stimulation (OKS).

METHODS

The effect of alcohol was tested in 14 subjects over multiple rounds of alcohol consumption up to a maximum breath alcohol concentration (BrAC) of 1.5‰ (mean 0.97‰). The effect of OKS was tested in 11 subjects at 5, 10 and 15deg/sec.

RESULTS

oVEMP amplitude decreased from baseline to the highest BrAC level by 27% (range 5-50%, P<0.001), but there was no significant effect on oVEMP latency or cVEMP amplitude or latency. There was a significant negative effect of OKS on oVEMP amplitude (16%, P=0.006).

CONCLUSIONS

We found a selective effect of alcohol on oVEMP amplitude, but no effect on the cVEMP. Vertical nystagmus elicited by OKS reduced oVEMP amplitude.

SIGNIFICANCE

Alcohol selectively affects oVEMP amplitude. Despite the effects of alcohol and nystagmus, both reflexes were reliably recorded in all subjects and conditions. An absent response in a patient affected by alcohol or nystagmus indicates a vestibular deficit.

Static posturography in addicted to illicit drugs and alcohol

The use of illicit drugs and alcohol can affect body balance.

AIM

To evaluate balance control with static posturography in individuals addicted to illicit drugs, with or without alcohol abuse.

STUDY DESIGN

Case-control, prospective.

METHODS

47 users of illicit drugs, with or without alcohol abuse, and a homogeneous control group consisting of 47 healthy individuals were submitted to a neurotological evaluation including Balance Rehabilitation Unit posturography.

RESULTS

The stability threshold mean values were significantly lower (p < 0.0001) in users of illicit drugs, with or without alcohol abuse when compared to the control group; the mean values for sway velocity and ellipse area in all evaluated conditions were significantly higher (p <0.05) in the experimental group when compared to the control group, except for the ellipse area in static force surface and opened eyes (p = 0.168).

CONCLUSION

The balance control of individuals addicted to illicit drugs with or without alcohol abuse could present stability threshold, sway velocity and ellipse area abnormalities in static posturography.

Study I: effects of 0.06% and 0.10% blood alcohol concentration on human postural control

Alcohol intoxication causes many accidental falls presented at emergency departments, with the injury severity often related to level of blood alcohol concentration (BAC). One way to evaluate the decline in postural control and the fall risk is to assess standing stability when challenged. The study objective was to comprehensively investigate alcohol-related impairments on postural control and adaptive motor learning at specific BAC levels. Effects of alcohol intoxication at 0.06% and 0.10% BAC were examined with posturography when unperturbed or perturbed by calf vibration. Twenty-five participants (mean age 25.1 years) were investigated standing with either eyes open or closed. Our results revealed several significant findings: (1) stability declined much faster from alcohol intoxication between 0.06% and 0.10% BAC (60-140%) compared with between 0.0% and 0.06% BAC (30%); (2) sustained exposure to repeated balance perturbations augmented the alcohol-related destabilization; (3) there were stronger effects of alcohol intoxication on stability in lateral direction than in anteroposterior direction; and (4) there was a gradual degradation of postural control particularly in lateral direction when the balance perturbations were repeated at 0.06% and 0.10% BAC, indicating adaptation deficits when intoxicated. To summarize, alcohol has profound deteriorating effects on human postural control, which are dose dependent, time dependent and direction specific. The maximal effects of alcohol intoxication on physiological performance might not be evident initially, but may be revealed first when under sustained sensory-motor challenges.

Human and laboratory rodent low response to alcohol: is better consilience possible?

If people are brought into the laboratory and given alcohol, there are pronounced differences among individuals in many responses to the drug. Some participants in alcohol challenge protocols show a cluster of 'low level of responses to alcohol' determined by observing post-drinking-related changes in subjective, motor and physiological effects at a given dose level. Those individuals characterized as having low level of response (LR) to alcohol have been shown to be at increased risk for a lifetime diagnosis of alcohol dependence (AD), and this relationship between low LR and AD appears to be in part genetic. LR to alcohol is an area where achieving greater consilience between the human and the rodent phenotypes would seem to be highly likely. However, despite extensive data from both human and rodent studies, few attempts have been made to evaluate the human and animal data systematically in order to understand which aspects of LR appear to be most directly comparable across species and thus the most promising for further study. We review four general aspects of LR that could be compared between humans and laboratory animals: (1) behavioral measures of subjective intoxication; (2) body sway; (3) endocrine responses; and (4) stimulant, autonomic and electrophysiological responses. None of these aspects of LR provide completely face-valid direct comparisons across species. Nevertheless, one of the most replicated findings in humans is the low subjective response, but, as it may reflect either aversively valenced and/or positively valenced responses to alcohol as usually assessed, it is unclear which rodent responses are analogous. Stimulated heart rate appears to be consistent in animal and human studies, although at-risk subjects appear to be more rather than less sensitive to alcohol using this measure. The hormone and electrophysiological data offer strong possibilities of understanding the neurobiological mechanisms, but the rodent data in particular are rather sparse and unsystematic. Therefore, we suggest that more effort is still needed to collect data using refined measures designed to be more directly comparable in humans and animals. Additionally, the genetically mediated mechanisms underlying this endophenotype need to be characterized further across species.

Alcohol intoxication at 0.06 and 0.10% blood alcohol concentration changes segmental body movement coordination

Alcohol intoxication is the cause of many falls requiring emergency care. The control of upright standing balance is complex and comprises contributions from several partly independent mechanisms like coordination, feedback and feedforward control and adaptation. Analysis of the segmental body movement coordination offers one option to detect the severity of balance problems. The study aims were (1) to investigate whether alcohol intoxication at 0.06 and 0.10% blood alcohol concentration (BAC) affected the segmental movement pattern under unperturbed and perturbed standing; (2) whether alcohol affected the ability for movement pattern adaptation; (3) whether one's own subjective feeling of drunkenness correlated to the movement pattern used. Twenty-five participants (13 women and 12 men, mean age 25.1 years) performed tests involving alcohol intoxication. Body movements were recorded at five locations (ankle, knee, hip, shoulder and head) during quiet standing and pseudorandom pulses of calf muscle vibration for 200 s with eyes closed or open. There was no significant effect of alcohol on the general movement pattern in unperturbed stance or on adaptation. However, when balance was repeatedly perturbed, knee movements became significantly less correlated to other body movements over time at 0.10% BAC and when visual information was unavailable, suggesting that the normal movement pattern could not be maintained for a longer period of time while under 0.10% BAC intoxication. Subjective feelings of drunkenness correlated often with a changed upper body movement pattern but less so with changed knee movements. Thus, an inability to relate drunkenness with changed knee movements may be a contributing factor to falls in addition to the direct effect of alcohol intoxication.

Alcohol and Its Impact on Motor Control

Acute and chronic alcohol intoxications have particularly deleterious consequences on physiological processes involving motor control and balance. This paper describes alcohol impairments to the central motor system networks in social and heavy drinkers and in individuals dependent on alcohol with or without neurological diseases.

Postural control in patients with liver cirrhosis: a posturographic study

BACKGROUND

Ataxia has been suggested in the literature to be a symptom of hepatic encephalopathy (HE), but so far has not been objectively quantified. In this study, we wanted to objectively quantify ataxia in patients with liver cirrhosis.

METHODS

One hundred and seven patients with liver cirrhosis were tested for postural control using posturography and compared with 25 controls. For quantification of HE, we used the number connection tests A and B, ammonia levels (NH3), and the partial pressure of ammonia in the arterial blood (pNH3).

RESULTS

Patients showed an impaired postural control compared with controls. Patients with Child C cirrhosis had lower scores in the posturography than those with Child A or B cirrhosis. Patients with alcohol-induced (AIC) Child B cirrhosis achieved lower scores in the posturography than those with non-alcohol-induced (NAIC) Child B cirrhosis. Patients with AIC Child C had lower scores than the corresponding NAIC patients, although this did not reach statistical significance. In the NAIC group Child C patients, in the AIC group Child B and C patients had lower scores than the controls. Patients with abnormal results in the number connection tests, as well as those with high NH3 and pNH3 levels showed worse postural control than those with normal results.

CONCLUSION

Patients with cirrhosis have an impaired postural control compared with controls and this impairment deteriorates with progression of liver disease. HE as well as past alcohol abuse contribute to the pathogenesis of ataxia in liver cirrhosis and past alcohol abuse leads to an earlier and more pronounced manifestation of ataxia in the affected patients.

Effect of Ethanol on Visual-Vestibular Interactions During Vertical Linear Body Acceleration

BACKGROUND

Ethanol led to disturbed dynamic visual acuity (DVA) during vertical linear acceleration (VLA; amplitude, 5 cm; frequency, 1.2 Hz). The aim of this study was to analyze whether suppression of visual-oculomotor or vestibular pathway is responsible for the disturbance of DVA.

METHODS

Twenty volunteers were investigated before and after ethanol consumption (mean breath alcohol concentration, 0.32 mg/liter). Vertical eye movements and linear head acceleration were recorded. Tested stimuli were vestibular (VLA in the dark), visual (smooth pursuit), and combined (VLA plus fixation on an earth-fixed target) stimulation; visual suppression (VLA plus fixation of a head-fixed target); static visual acuity; and DVA. Parameters of analysis were gain, sensitivity, eye velocity and amplitude, latency between onset of head acceleration and start of eye movement, correct and wrong answers during static visual acuity and DVA testing, feeling of drunkenness (FOD), and breath alcohol concentration.

RESULTS

Both during isolated visual and during combined visual-vestibular stimulation, alcohol induced a significant latency increase. Furthermore, DVA was disturbed after ethanol consumption. Test subjects with a strong alcohol-induced disturbance of DVA presented during isolated visual stimulation a significantly higher latency change than volunteers with a minor alcohol-induced disturbance of DVA. On the basis of the FOD, two groups were formed (one with a slight and one with a strong FOD). The two groups differed significantly concerning the alcohol-induced latency increase during isolated visual stimulation and the alcohol-induced disturbance of DVA.

CONCLUSIONS

Ethanol leads to a disturbance of the visual-oculomotor system and, thus, even during combined visual-vestibular stimulation, to a latency increase. This "delay" is responsible for the disturbance of DVA. This alcohol-induced suppression of the visual-oculomotor system and the disturbance of DVA show a significantly positive correlation with the subjective FOD.

Computerised dynamic posturography to assess recovery comparing general anaesthesia with sedation and local anaesthesia for day case nasal surgery

Computerised dynamic posturography (CDP) can be used as an early marker of recovery to street fitness in patients undergoing ambulatory surgery. We studied three groups of patients undergoing nasal surgery. The goal of this study was to determine whether recovery, as assessed by CDP, is more rapid in patients having nasal surgery under sedation coupled with local anaesthesia or those having surgery under general anaesthesia. We further assessed the acceptability of sedation accompanied by local anaesthesia. A control group was included to determine if there is a learning curve to posturography. There was no difference between the two study groups in terms of balance. Balance was not significantly impaired at 3 h postoperative testing.

Postural control and lifetime alcohol consumption in alcohol-dependent patients

OBJECTIVES

The aim of this study was to examine the relationship between alcohol consumption and postural control in alcohol-dependent patients.

MATERIAL AND METHODS

Posturographic measurements were performed in 82 abstinent patients and in 54 healthy controls. The findings in the patients were compared with those in the controls as well as with the daily alcohol consumption, the consumption during 6 months before the admission for alcohol withdrawal therapy and the estimated lifetime alcohol consumption.

RESULTS

Postural control was impaired in alcohol-dependent patients compared to healthy controls. This impairment was related with the lifetime alcohol consumption, but not with the alcohol consumption per day and prior to admission, respectively. Comparing healthy controls, and alcohol-dependent patients with an estimated lifetime alcohol consumption of < 1000 kg and > or = 1000 kg revealed a significant increase in 6 of 8 sway parameters. Furthermore, the lifetime alcohol consumption increased significantly from patients with normal posturographic and clinical findings to those with abnormalities in both examinations.

CONCLUSION

This study suggests that postural imbalance in abstinent alcohol-dependent patients is related to the lifetime alcohol consumption.

Alcohol and injuries in elderly people

Injuries are a common cause of morbidity and mortality among elderly people. Falls are the most common type of accident, accounting for around 40% of injuries. There is substantial evidence that heavy alcohol use is an important risk factor for injuries in younger people, but results of the few studies of alcohol and injuries among elderly people have been inconsistent. In this paper, we review the literature on the effects of alcohol on gait and balance and present reasons that a causal relationship between alcohol and injuries is biologically plausible. We review the epidemiological studies of the relationship between alcohol and falls, hip fractures and other injuries in the elderly population and discuss sources of error in these studies. Selection bias, small sample sizes, measurement error and potential confounders such as age, gender, health status and medications may have played a substantial role in negative results from several studies. Further research that will help clarify the relationship between alcohol and injuries in elderly people is sorely needed.