The influence of fasting and of caffeine intake on finger tremor

In Situ Tremor in Vitreoretinal Surgery

OBJECTIVE

Surgeon tremor was measured during vitreoretinal microscopic surgeries under different hand support conditions.

BACKGROUND

While the ophthalmic surgeon's forearm is supported using a standard symmetric wrist rest when operating on the patient's same side as the dominant hand (SSD), the surgeon's hand is placed directly on the patient's forehead when operating on the contralateral side of the dominant hand (CSD). It was hypothesized that more tremor is associated with CSD surgeries than SSD surgeries and that, using an experimental asymmetric wrist rest where the contralateral wrist bar gradually rises and curves toward the patient's operative eye, there is no difference in tremor associated with CSD and SSD surgeries.

METHODS

Seventy-six microscope videos, recorded from three surgeons performing macular membrane peeling operations, were analyzed using marker-less motion tracking, and movement data (instrument path length and acceleration) were recorded. Tremor acceleration frequency and magnitude were measured using spectral analysis. Following 47 surgeries using a conventional symmetric wrist support, surgeons incorporated the experimental asymmetric wrist rest into their surgical routine.

RESULTS

There was 0.11 mm/s² (22%) greater (p = .05) average tremor acceleration magnitude for CSD surgeries (0.62 mm/s², SD = 0.08) than SSD surgeries (0.51 mm/s², SD = 0.09) for the symmetric wrist rest, while no significant (p > .05) differences were observed (0.57 mm, SD = 0.13 for SSD and 0.58 mm, SD = 0.11 for CSD surgeries) for the experimental asymmetric wrist rest.

CONCLUSION

The asymmetric wrist support reduced the difference in tremor acceleration between CSD and SSD surgeries.

Tremors: Essential Tremor and Beyond

Tremor is a fairly common movement disorder presenting to an outpatient pediatric neurology practice. Tremors can be primary or secondary to underlying neurologic or systemic diseases. When assessing a child with tremor, it is paramount to evaluate the phenomenology of the tremor, determine the presence or absence of other neurologic signs and symptoms, and the possible modifying influence of medications. Proper classification is essential for specific diagnosis and prompt adequate management. Treatment considerations should take into account objective assessment of tremor severity and the degree of disability or impairment experienced by the child. Overall effectiveness of pharmacologic treatments of tremor is unfortunately disappointing. In this article we review the clinical examination, classification, and diagnosis of tremor. The pathophysiology of the different forms of tremor is outlined, and treatment options are discussed.

Comparison of training effect on tremor using 2 training modules

PURPOSE

To compare training effect of 2 training models-a surgical simulator anti-tremor module and a paper version-on tremor and time-to-task completion.

SETTING

Ophthalmology Department, Veterans Affairs Boston Healthcare System, Jamaica Plain, Massachusetts, USA.

DESIGN

Prospective crossover study.

METHODS

Trainees completed simulator and paper training modules (baseline test, 3 training sessions, posttraining test, and final test) with their dominant and nondominant hands. The change in tremor, number of paper errors, and time-to-task completion in dominant and nondominant hands were compared. The 2 training modules were compared using nonparametric tests.

RESULTS

The study comprised 19 trainees. There was a moderate correlation between average tremor values (simulator, 3-dimensional module) and paper errors (paper, 2-dimensional module) (Spearman ⍴ = 0.35, P < .0001). Practice on the simulator or paper modules did not reduce tremor significantly from baseline to final tasks for both hands combined (P = .12, simulator; P = .2, paper). Practice on the training modules improved time-to-task completion in the simulator module and paper module (both P < .0001). The improvement in time from baseline to final tasks was greater in the nondominant hands in the simulator module (improvement 64.5% over baseline time) than in the paper module (53.6% over baseline time).

CONCLUSION

Practice might not reduce tremor but improved the outcome measure of time, and results suggest that trainees can learn to compensate for tremor in both hands, which is important in bimanual microsurgery.

The influence of muscle tremor on shooting performance

Shooting ability is compromised by involuntary movement. Some of this movement is physiological tremor. Tremor size has a demonstrable inverse correlation with shooting performance. Consequently, factors which affect tremor size should affect shooting ability. Adrenaline and local muscle warming markedly increase tremor size, whereas local muscle cooling reduces it. The physiological mechanisms behind these changes are not well understood, but they have the potential to affect shooting performance in subjects who exercise heavily and/or are exposed to extreme environments. The Olympic biathlon is an event in which vigorous physical exercise alternates with rifle shooting and it often takes place in a cold environment. The possible impact of exercise, temperature and other factors on the Olympic biathlete is considered here.

Kinetic tremor: differences between smokers and non-smokers

Tremor is among the acute effects of nicotine exposure. Published studies have focused on smoking-related postural (static) hand tremor rather than kinetic tremor (tremor during hand use), and gender differences in smoking-related tremor have not been examined. In a group of adults who were sampled from a population (mean+/-S.D.=65.7+/-11.5 years, range=18-92 years), the investigator assessed whether the severity of postural and kinetic tremors differed in smokers versus non-smokers, and whether this difference was influenced by gender. Twenty-seven (9.9%) of 273 subjects were current smokers. Greater tremor was observed in smokers than non-smokers during a variety of activities (drawing a spiral, using a spoon, finger-nose-finger maneuver, all p<0.05) and smokers had a higher total tremor score than non-smokers (5.15+/-3.06 versus 3.41+/-2.88, p<0.01), even after adjusting for age, caffeine intake and other potential confounding factors. The difference between smokers and non-smokers in terms of hand tremor was more apparent in women than in men. In women, the number of cigarettes smoked on the day of testing was weakly correlated with the total tremor score (r=0.17, p=0.03). In summary, smokers had more kinetic hand tremor than non-smokers. This difference between smokers and non-smokers was more apparent in women than in men. These results suggest that smoking habits should be considered carefully in order to avoid over- or underestimating the effects of occupational and non-occupational exposures to other tremor-producing neurotoxins.

Exploring the relationship between caffeine intake and essential tremor

BACKGROUND

It has been suggested that environmental factors may be associated with essential tremor (ET). This study was carried out to evaluate the association of caffeine intake with ET.

METHOD

In a case control study, patients diagnosed with ET and healthy controls underwent a standardized questionnaire interview to evaluate the exposure to coffee and tea intake. A multivariate logistic regression analysis was carried out to evaluate the association of caffeine intake and other environmental factors with risk of ET.

RESULTS

179 subjects including 79 ET patients and 100 controls matched for age, gender and ethnicity were included in the analysis. Univariate analysis revealed that caffeine consumption in ET patients was higher than control group (median and 90th percentile range: 2300 (0, 9000) mg-years versus 1500 (0, 6090) mg-years, p=0.01). However, the multivariate logistic regression analysis demonstrated that caffeine was no longer a significant factor associated with ET (p=0.119). There was no significant correlation between amount of caffeine intake and disease duration (Spearman's r=0.194; p=0.202) or total tremor score (Spearman's r=0.045; p=0.771) in ET patients.

CONCLUSION

Caffeine consumption was not associated with risk of ET in our study population. Further studies are needed to investigate the significance of gene-environmental interaction in ET.

Drug-induced tremors

Tremor is a common complaint for many patients. Caffeine and beta-adrenergic agonists are well-recognised drugs that cause or exacerbate tremors. Other tremorogenic drugs, such as selective serotonin reuptake inhibitors and tricyclic antidepressants, are less well recognised. Recognition of the drugs that can cause or exacerbate tremors can help prompt diagnosis, avoids unnecessary tests, and allows clinicians to quickly take corrective action (usually by discontinuing the tremor-inducing drugs). The aim of this review is to provide clinicians with current information on drugs that are associated with tremor and the correct treatment of these drug-induced tremors.

Semiquantitative study of current coffee, caffeine, and ethanol intake in essential tremor cases and controls

There are several reasons to study caffeine, coffee, and ethanol intake in essential tremor (ET) patients. ET patients also might modify their use of these beverages because of their effects on tremor. Intake of caffeine, coffee, and ethanol has not been quantified in a group of ET patients. Our objective is to use a semiquantitative food frequency questionnaire to compare current daily intake of coffee, caffeine, and ethanol in ET patients and controls. A total of 130 ET cases were patients at the Neurological Institute of New York, and 175 controls were ascertained by random digit dialing. Caffeine (in milligrams) and ethanol (in grams) intake were calculated from a semiquantitative food-frequency questionnaire. Mean daily caffeine intake in patients was 138.4 versus 246.6 mg in controls; medians were 101.1 versus 175.5 mg (P < 0.001). Mean daily ethanol intake in patients was 8.2 versus 6.2 gm in controls; medians were 2.4 versus 1.9 gm (P = 0.89). Cases drank less coffee than controls, but drank similar amounts of tea, soft drinks, fruit juices, and milk. Daily caffeine intake was not correlated with tremor severity or duration. ET patients consumed less caffeine than did controls, which is likely to be a dietary modification in response to tremor. The observation that caffeine consumption was not correlated with tremor severity raises the additional possibility that lower caffeine consumption in ET patients may not exclusively be a response to tremor. A prospective study is needed to explore whether decreased caffeine consumption is a risk factor for ET.

Phenomenology and treatment of tremor disorders

Tremor is classified according to anatomic distribution among body parts, and by frequency and amplitude during rest, postural maintenance, movement, intention, and the performance of specific tasks. Key historical features include age at onset, progression over time, family history, exacerbating and remitting factors and behaviors, response to alcohol and medications, and additional neurological signs and symptoms. Accurate diagnosis is a critical factor in predicting the natural history and response to treatment.

Caffeine influence on the motor steadiness battery in neuropsychological tests

Caffeine is a widely used drug with various biological effects. The present investigation focuses on a possible influence of caffeine upon motor steadiness performance in tests routinely used in neuropsychological testing. Twenty-four healthy females between 23 and 38 years were investigated in a randomised double-blind crossover study. A significantly poorer motor steadiness performance was found after ingestion of 300 mg of caffeine as compared to a placebo (decaffeinated coffee). Both error time and error count were increased after caffeine consumption. Caffeine also tended to reduce maze coordination test performance. We conclude that caffeine intake preferably should be avoided before neuropsychological testing of motor steadiness.

Effect of caffeine on motor performance by caffeine-naive and -familiar subjects

The purpose of this investigation was to assess the effect of caffeine on selected manipulation skills by caffeine-naive and caffeine-familiar subjects. The subjects were 20 caffeine-naive (less than 90 mg/d) and 20 caffeine-familiar (greater than 750 mg/d) college-age (21 +/- 1.7 yr.) women. Measurements included steadiness error time and frequency, duration of tracing, error time and frequency, and dexterity. Doses of 2.5, 5.0 mg.kg-1 body weight caffeine or a placebo (200 mg. methylcellulose) were administered randomly to all subjects on three separate occasions. A 2 x 3 repeated-measures analysis of variance yielded a significant group difference for steadiness error time between the 5 mg.kg-1 and 2.5 mg.kg-1 dose and between 5 mg.kg-1 and the placebo. For frequency of steadiness errors, the nonuser group posted significant gains for both 5.0 and 2.5 mg.kg-1 over the placebo control. On tracing error time and error frequency, 5.0 mg.kg-1 resulted in significant increases from both 2.5 mg.kg-1 and the placebo group. In the caffeine-naive group, both doses of caffeine led to significant increases in dexterity time from the placebo, and the 5.0 mg.kg-1 dose was significantly different from the 2.5 mg.kg-1 trial. It was concluded that caffeine had detrimental effects on selected performance skills of caffeine-naive women but not in caffeine-familiar women.

Influence of caffeine on selected manual manipulation skills

To assess the effects of caffeine on selected manual manipulation skills 16 college-age (21 +/- 1.7 yr.) caffeine-naive women (less than 90 mg/day), having avoided products containing caffeine for four days, reported for testing eight hours postprandial. Measurements included duration and frequency of error for hand steadiness, duration and frequency error for following a tracing pattern, and duration of completing a tweezer-pin placement dexterity test. Caffeine doses of either 2.5 or 5.0 mg/kg body weight or a placebo (200 mg. methylcellulose) were administered randomly to all subjects on three separate occasions using a double-blind format. A 2 x 3 repeated-measures analysis of variance and a Newman-Keuls post hoc test yielded a significant difference in hand steadiness error time from pre- to posttest for 5 mg/kg but not for 2.5 mg/kg or the placebo trial. For frequency of hand steadiness error, significant changes occurred for both 5.0 and 2.5 mg/kg. A dose of 5.0 mg/kg group resulted in significant differences in both tracing error time and error frequency. As both doses of caffeine significantly increased dexterity time, it was concluded that caffeine has detrimental effects on selected performance skills of young caffeine-naive women.

The pharmacology of human anxiety

The human pharmacology of anxiety disorders, including panic disorder, is detailed. The major theories center around the role of benzodiazepine receptor, noradrenergic and serotonergic dysfunction. The contribution that challenge tests with lactate, hyper- and hypocapnia, beta- and alpha-2-adrenoceptor agonists, peptides, pentylenetetrazol, and caffeine make to our understanding of the biological basis of anxiety and these major theories are described and discussed.

An assessment of the partial agonist activity of Ro 31-1118, flusoxolol and pindolol in man

1. The effects of single oral doses of three beta-adrenoceptor partial agonists (Ro 31-1118, flusoxolol and pindolol), two beta-adrenoceptor antagonists (propranolol and atenolol), two beta-adrenoceptor agonists (salbutamol and prenalterol) and placebo on sleeping heart rate, quality of sleep, supine heart rate, exercise heart rate, blood pressure, forearm blood flow and finger tremor were studied in eight healthy male volunteers. 2. Sleeping heart rate was increased by Ro 31-1118, flusoxolol, pindolol, salbutamol and prenalterol and decreased by propranolol and atenolol. 3. None of the drugs studied affected quality of sleep. 4. Supine heart rate was increased by flusoxolol, prenalterol and salbutamol, unaffected by Ro 31-1118 and pindolol and reduced by propranolol and atenolol. 5. Exercise heart rate was reduced by both beta-adrenoceptor antagonists and the three partial agonists and unaffected by salbutamol and prenalterol. 6. Systolic blood pressure was increased by Ro 31-1118, flusoxolol, salbutamol and prenalterol, unaffected by pindolol and reduced by propranolol and atenolol. Diastolic blood pressure was reduced by salbutamol and prenalterol. 7. Forearm blood flow was increased by Ro 31-1118, salbutamol and prenalterol, unchanged by pindolol and flusoxolol and decreased by atenolol and propranolol. 8. Finger tremor was increased by Ro 31-1118, flusoxolol, pindolol, salbutamol, and prenalterol. 9. beta-adrenoceptor partial agonists have different effects on the cardiovascular system and finger tremor to beta-adrenoceptor antagonists. 10. While Ro 31-1118 and flusoxolol are antagonists mainly at the beta 1-adrenoceptor they have agonist activity at both beta 1- and beta 2 adrenoceptors. 11. While pindolol is a non-selective antagonist its agonist activity is mainly at the beta 2-adrenoceptor.

States of anxiety and their induction by drugs

Syndromes of anxiety include generalized anxiety states, various forms of phobic disorder and panic attacks. It is unclear whether panic attacks are a separate syndrome from anxiety states or a more severe form. Drug-induced states of anxiety should provide useful models of the mechanisms of anxiety and its treatment. High-risk populations might be identifiable. Catecholamine infusions produce marked peripheral changes without fully reproducing the central feelings. Lactate infusions also produce anxiety-like states lacking full credibility. Experience with the benzodiazepine-receptor contragonists, the beta-carbolines, is limited but panic states have been reproduced following their use. Caffeine produces an anxiety state in high dose and some panic states have been induced. The critical evaluation of drug-induced anxiety states is a promising way of elucidating the mechanisms, psychological and physiological, associated with clinical anxiety.