Diurnal variation of essential and physiological tremor

How Does Chronobiology Contribute to the Development of Diseases in Later Life

An increasingly older population is one of the major social and medical challenges we currently face. Between 2010 and 2050, it is estimated that the proportion of adults over 65 years of age will double from 8% to 16% of the global population. A major concern associated with aging is the changes in health that can lead to various diseases such as cancer and neurogenerative diseases, which are major burdens on individuals and societies. Thus, it is imperative to better understand changes in sleep and circadian rhythms that accompany aging to improve the health of an older population and target diseases associated with aging. Circadian rhythms play a role in most physiological processes and can contribute to age-related diseases. Interestingly, there is a relationship between circadian rhythms and aging. For example, many older adults have a shift in chronotype, which is an individual's natural inclination to sleep certain times of the day. As adults age, most people tend to go to sleep earlier while also waking up earlier. Numerous studies also suggest that disrupted circadian rhythms may be indicative of developing age-related diseases, like neurodegenerative disorders and cancer. Better understanding the relationship between circadian rhythms and aging may allow us to improve current treatments or develop novel ones that target diseases commonly associated with aging.

Holmes tremor: a delayed complication after resection of brainstem cavernomas

OBJECTIVE

In this paper, the authors aimed to illustrate how Holmes tremor (HT) can occur as a delayed complication after brainstem cavernoma resection despite strict adherence to the safe entry zones (SEZs).

METHODS

After operating on 2 patients with brainstem cavernoma at the Great Metropolitan Hospital Niguarda in Milan and noticing a similar pathological pattern postoperatively, the authors asked 10 different neurosurgery centers around the world to identify similar cases, and a total of 20 were gathered from among 1274 cases of brainstem cavernomas. They evaluated the tremor, cavernoma location, surgical approach, and SEZ for every case. For the 2 cases at their center, they also performed electromyographic and accelerometric recordings of the tremor and evaluated the post-operative tractographic representation of the neuronal pathways involved in the tremorigenesis. After gathering data on all 1274 brainstem cavernomas, they performed a statistical analysis to determine if the location of the cavernoma is a potential predicting factor for the onset of HT.

RESULTS

From the analysis of all 20 cases with HT, it emerged that this highly debilitating tremor can occur as a delayed complication in patients whose postoperative clinical course has been excellent and in whom surgical access has strictly adhered to the SEZs. Three of the patients were subsequently effectively treated with deep brain stimulation (DBS), which resulted in complete or almost complete tremor regression. From the statistical analysis of all 1274 brainstem cavernomas, it was determined that a cavernoma location in the midbrain was significantly associated with the onset of HT (p < 0.0005).

CONCLUSIONS

Despite strict adherence to SEZs, the use of intraoperative neurophysiological monitoring, and the immediate success of a resective surgery, HT, a severe neurological disorder, can occur as a delayed complication after resection of brainstem cavernomas. A cavernoma location in the midbrain is a significant predictive factor for the onset of HT. Further anatomical and neurophysiological studies will be necessary to find clues to prevent this complication.

An Update on the Neurochemistry of Essential Tremor

Background:

The pathophysiology and neurochemical mechanisms of essential tremor (ET) are not fully understood, because only a few post-mortem studies have been reported, and there is a lack of good experimental model for this disease.

Objective:

The main aim of this review is to update data regarding the neurochemical features of ET. Alterations of certain catecholamine systems, the dopaminergic, serotonergic, GABAergic, noradrenergic, and adrenergic systems have been described, and are the object of this revision.

Methods:

For this purpose, we performed a literature review on alterations of the neurotransmitter or neuromodulator systems (catecholamines, gammaaminobutyric acid or GABA, excitatory amino acids, adenosine, T-type calcium channels) in ET patients (both post-mortem or in vivo) or in experimental models resembling ET.

Results and Conclusion:

The most consistent data regarding neurochemistry of ET are related with the GABAergic and glutamatergic systems, with a lesser contribution of adenosine and dopaminergic and adrenergic systems, while there is not enough evidence of a definite role of other neurotransmitter systems in ET. The improvement of harmaline-induced tremor in rodent models achieved with T-type calcium channel antagonists, cannabinoid 1 receptor, sphingosine-1-phosphate receptor agonists, and gap-junction blockers, suggests a potential role of these structures in the pathogenesis of ET.

Exploring the Relationship of Task Performance and Physical and Cognitive Fatigue During a Daylong Light Precision Task

OBJECTIVE

Our aim was to explore the relationship between fatigue and operation system performance during a simulated light precision task over an 8-hr period using a battery of physical (central and peripheral) and cognitive measures.

BACKGROUND

Fatigue may play an important role in the relationship between poor ergonomics and deficits in quality and productivity. However, well-controlled laboratory studies in this area have several limitations, including the lack of work relevance of fatigue exposures and lack of both physical and cognitive measures. There remains a need to understand the relationship between physical and cognitive fatigue and task performance at exposure levels relevant to realistic production or light precision work.

METHOD

Errors and fatigue measures were tracked over the course of a micropipetting task. Fatigue responses from 10 measures and errors in pipetting technique, precision, and targeting were submitted to principal component analysis to descriptively analyze features and patterns.

RESULTS

Fatigue responses and error rates contributed to three principal components (PCs), accounting for 50.9% of total variance. Fatigue responses grouped within the three PCs reflected central and peripheral upper extremity fatigue, postural sway, and changes in oculomotor behavior.

CONCLUSION

In an 8-hr light precision task, error rates shared similar patterns to both physical and cognitive fatigue responses, and/or increases in arousal level.

APPLICATION

The findings provide insight toward the relationship between fatigue and operation system performance (e.g., errors). This study contributes to a body of literature documenting task errors and fatigue, reflecting physical (both central and peripheral) and cognitive processes.

Sensitivity, reliability and the effects of diurnal variation on a test battery of field usable upper limb fatigue measures

Fatigue has been linked to deficits in production quality and productivity and, if of long duration, work-related musculoskeletal disorders. It may thus be a useful risk indicator and design and evaluation tool. However, there is limited information on the test-retest reliability, the sensitivity and the effects of diurnal fluctuation on field usable fatigue measures. This study reports on an evaluation of 11 measurement tools and their 14 parameters. Eight measures were found to have test-retest ICC values greater than 0.8. Four measures were particularly responsive during an intermittent fatiguing condition. However, two responsive measures demonstrated rhythmic behaviour, with significant time effects from 08:00 to mid-afternoon and early evening. Action tremor, muscle mechanomyography and perceived fatigue were found to be most reliable and most responsive; but additional analytical considerations might be required when interpreting daylong responses of MMG and action tremor. Practitioner Summary: This paper presents findings from test-retest and daylong reliability and responsiveness evaluations of 11 fatigue measures. This paper suggests that action tremor, muscle mechanomyography and perceived fatigue were most reliable and most responsive. However, mechanomyography and action tremor may be susceptible to diurnal changes.

Effect of levodopa-carbidopa intestinal gel on resting tremors in patients with advanced Parkinson's disease

Resting tremors occur in more than 70% of patients with advanced Parkinson’s disease (PD). PD patients with resting tremors are typically treated with oral dopaminergic therapy or non-dopaminergic agents. However, treatment response with these medications is inconsistent and often unsatisfactory. Levodopa-carbidopa intestinal gel (LCIG, also known in the United States as carbidopa-levodopa enteral suspension (CLES)), administered continuously by a portable pump via a percutaneous endoscopic gastrojejunostomy (PEG-J) tube, significantly improves motor complications in patients with advanced PD. This was a post hoc analysis of a large phase 3, 12-month, open-label study evaluating long-term safety and efficacy of LCIG via PEG-J tube (NCT00335153). Unified Parkinson’s Disease Rating Scale Part III Question 20 total scores at baseline, measuring resting tremors, were used to stratify patients into three subgroups (none, mild, or significant baseline resting tremors). Out of 354 enrolled patients, 286 had baseline and post-PEG-J assessments of resting tremors and were included in this analysis. At baseline the majority of patients (69%) had no resting tremors, whereas 13% had mild resting tremors, and 18% had significant resting tremors. A complete resolution in resting tremors after 12 months of LCIG treatment was reported for 78% and 70% of patients with mild and significant baseline resting tremors, respectively. Improvements in motor complications and quality of life occurred regardless of degree of baseline resting tremors. LCIG may provide more consistent and sustained improvements in resting tremors that were not well-controlled with optimized oral medication among patients with advanced PD.

Testing for alcohol sensitivity of tremor amplitude in a large cohort with essential tremor

BACKGROUND

Improvement of essential tremor (ET) amplitude after alcohol ingestion is usually based on patient reports but a quantitative test for large numbers of patients is lacking and the percentage of ET patients with a detectable alcohol effect is therefore unknown.

METHODS

A validated and published alcohol home test was used in 104 ET patients. The Archimedes spiral was drawn before alcohol ingestion and at 4 time points after alcohol consumption and rated on a 10-point rating scale according to Bain and Findley. A second identical test without alcohol ingestion was performed by the same patients and evaluated by the same two raters to analyze the total variability of the spiral ratings.

RESULTS

Alcohol reduces tremor in ET patients as a group and a rebound effect with an increase in tremor intensity was found the next morning. Sex, family history of ET, diagnosis (definite vs. probable) and medical history of alcohol responsiveness do not predict the alcohol response. The minimal detectable difference in the spiral score was 2 due to spontaneous tremor fluctuations and inter-rater differences. The test demonstrated alcohol sensitivity of the tremor in 46% of the patients. Responsivity to alcohol could only be seen in patients with spiral scores above 3.

CONCLUSIONS

Alcohol sensitivity is a feature of ET in at least 46% of the patients. We could not find predictors for alcohol sensitivity. The minimal detectable change is 2 scores and alcohol responsivity was only detected in patients with baseline Archimedes spiral rating of ≥3.

The effects of a novel histamine-3 receptor inverse agonist on essential tremor in comparison to stable levels of alcohol

Essential tremor (ET) is a common movement disorder. Animal studies show that histaminergic modulation may affect the pathological processes involved in the generation of ET. Histamine-3 receptor inverse agonists (H3RIA) have demonstrated attenuating effects on ET in the harmaline rat model. In this double-blind, three-way cross-over, single-dose, double-dummy study the effects of 25 mg of a novel H3RIA (MK-0249) and a stable alcohol level (0.6 g L(-1)) were compared with placebo, in 18 patients with ET. Tremor was evaluated using laboratory tremorography, portable tremorography and a clinical rating scale. The Leeds Sleep Evaluation Questionnaire (LSEQ) and a choice reaction time (CRT) test were performed to evaluate potential effects on sleep and attention, respectively. A steady state of alcohol significantly diminished tremor as assessed by laboratory tremorography, portable tremorography and clinical ratings compared with placebo. A high single MK-0249 dose was not effective in reducing tremor, but caused significant effects on the LSEQ and the CRT test. These results suggest that treatment with a single dose of MK-0249 does not improve tremor in alcohol-responsive patients with ET, whereas stable levels of alcohol as a positive control reproduced the commonly reported tremor-diminishing effects of alcohol.

The effects of TPA023, a GABAAα2,3 subtype-selective partial agonist, on essential tremor in comparison to alcohol

Essential tremor (ET) is a relatively frequent neurological disorder that responds in some patients to gamma-aminobutyric acid A (GABA(A)) agonists such as the benzodiazepines. Partial subtype-selective GABA(A) agonists may have an improved side effect profile compared to non-selective GABA(A) agonists. However, it is unknown which GABA(A) subtypes are involved in the therapeutic effects of benzodiazepines in ET. The effects of 2 mg TPA023, a GABA(A) α2,3 subtype-selective partial agonist, on ET were compared to the effects of a stable alcohol level (0.6 g/L) and placebo in nine patients with ET. Tremor evaluation included laboratory accelerometry and a performance-based scale. Additional measurements were performed to evaluate other effects on the central nervous system (CNS). Alcohol significantly diminished tremor symptoms in the postural and kinetic condition, as assessed by laboratory accelerometry, but the performance-based rating scale was unaffected. Tremor was also reduced after TPA023 treatment in the kinetic condition, albeit not significantly. Additionally, TPA023 decreased saccadic peak velocity, while alcohol decreased subjective feelings of alertness. This study showed that alcohol reduced maximum tremor power, as assessed by laboratory accelerometry, unlike TPA023, which decreased tremor symptoms to some extent but not significantly. This study showed that treatment with an α2,3 subunit-selective GABA(A) partial agonist was less effective than a stable level of alcohol in reducing ET symptoms. These results provide no support for a therapeutic role of TPA023 in the suppression of ET symptoms.

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.

Effects of Mixed Organic Solvents on Neuromotor Functions among Workers in Buddhist Altar Manufacturing Factories

To clarify the neuromotor effects of long-term exposure to mixed organic solvents, postural sway and tremor were measured in 62 solvent workers of four Buddhist altar manufacturing factories who had worked for 1-46 (mean 12) yr. By using the passive gas sampler, 8-h time-weighted average concentrations in the workers were estimated to be 0.02-8.7 ppm for toluene, 0.02-7.7 ppm for xylene, 0.02-5.5 ppm for styrene and 0.02-40.5 ppm for n-hexane. Sagittal sway and sway area of the posturography with eyes closed were significantly larger in the solvent workers than in 35 age-matched controls (p<0.05), and there was a significant difference in Romberg quotient of sagittal sway between the two groups (p<0.05). Also, tremor intensities at 1.0-5.9 Hz, 6.0-9.9 Hz and 10.0-13.9 Hz with the right hand, and at 6.0-9.9 Hz with the left hand were significantly stronger in the solvent workers than in the controls. Among the solvent workers, transversal and sagittal sways with eyes open and tremor intensity at 10.0-13.9 Hz were significantly related to toluene exposure (p<0.05), which may have been due to the acute effects of such solvents. These findings suggest that long-term exposure to mixed organic solvents may impair neuromotor functions as measured by postural sway and tremor.

Circadian patterns of neurotransmitter related gene expression in motor regions of the rat brain

Mammalian motor activity displays circadian patterns in normal behaviour and in many movement disorders, like levodopa responsive dystonia and Parkinson's disease. Here, we hypothesized that a circadian pattern of dopamine synthesis would trigger rhythms in the expression of genes in regions receiving dopaminergic innervation. Indeed tyrosine hydroxylase and cholecystokinin mRNA were upregulated in the substantia nigra and ventral tegmental area in the course of the day. However, in the caudate putamen, the mRNA levels, for dopamine D2 and adenosine 2A receptor, dynorphin, and substance P were lower during the day than during the night, whereas the expression of dopamine D1 receptor, enkephalin, and somatostatin was stable. In the frontal cortex, a clear midday peak of enkephalin expression was detected, while cholecystokinin and vasoactive intestinal peptide expression did not vary. Clear circadian gene expression patterns can therefore be demonstrated in brain regions involved in motor regulation, but they do not follow a simple dopaminergic drive and more complex regulatory patterns have to be assumed.

Clinical and electromyographic assessment of essential tremor treatment

It is a matter of debate whether beta-blockers or primidone have a better influence on essential tremor. It is also controversial whether essential tremor with synchronous electromyographic activity is influenced by the administration beta-blockers, while tremor with alternating electromyographic activity is influenced by primidone. The aim of this study was to reevaluate the effects of beta-blockers and primidone on essential tremor. We also aimed to evaluate the differential effects of beta-blockers and primidone on tremor with synchronous or alternating electromyographic activity and on tremor in different limb positions. One hundred patients (57 female, 43 male) with essential tremor were included in this study. According to the electromyographic pattern recorded from the antagonistic muscles, the patients were subdivided into group with synchronous (SYN) and group with alternating (ALT) activity. After the initial clinical and electromyographic examinations the patients were randomly assigned first to treatment with propranolol (180 mg daily), or to treatment with primidone (500 mg daily) for 30 days. After a washout period of 20 days the patients were assigned to the other treatment. Our results revealed that the effects of propranolol and primidone on essential tremor and on SYN or ALT tremor were similar. Differences between both drugs existed as regards to better primidone influence on the kinetic and intention tremors and to tremor localized outside the limbs. In conclusion it is better to treat patients with kinetic and intention essential tremor and tremor localized outside the limbs with primidone.

Electromyographic differentiation of tremors

OBJECTIVE

The aim of this study was to explore the opportunity for differentiation of tremors on the basis of the electromyographic examination.

METHODS

We report data from 525 patients with different types of tremor included in this study. Two hundred and twenty patients with essential tremor, 110 patients with Parkinson's disease, 24 patients with midbrain tremor, 22 patients with cerebellar tremor, 120 patients with enhanced physiological tremor due to anxiety, and 29 patients with psychogenic tremor participated in the study. A detailed neurological and electromyographic examination was performed. The tremor was studied in all limbs positions. Surface electromyographic recordings of the most involved body part were performed to all patients.

RESULTS

According to the electromyographic examination all patients were divided to two groups: Patients with synchronous tremor and patients with alternating tremor in the antagonist muscles. The comparisons were performed only between the patients with tremor caused by different etiology within the group of synchronous or alternating tremor. The group of tremors with synchronous pattern included the patients with essential tremor type A (with synchronous activity), cerebellar, and enhanced physiological tremor. The group of tremors with alternating pattern included patients with Parkinsonian tremor, essential tremor type B (with alternating activity), rubral, and psychogenic tremors. Our results revealed that electromyographic examination of tremor pattern, frequency, amplitude, and burst duration is useful for tremor differentiation.

CONCLUSION

The electromyographic examination may serve as a tool for differentiation of tremors.

Clinical and electromyographic examinations of Parkinsonian tremor

Background: The clinical presentations of postural Parkinsonian tremor are variable and different types of tremors have been described. The aim of this study was to re-evaluate the clinical and electromyographic (EMG) pattern of different tremors in Parkinsonian patients.Methods: One hundred and ten patients with Parkinsonian tremor were included in the study. Patients were subdivided into four groups according to the presence or absence of postural tremor, in addition to a resting tremor and its EMG pattern. The first group consisted of patients without postural tremor. The second group consisted of patients with fast postural tremor (>7Hz). The third group consisted of patients with slow postural tremor with alternating EMG activity. Patients with slow postural tremor with synchronous EMG activity were included in the fourth group. In each limb position, the tremor of the most involved body part was graded on the Webster Tremor Scale. Surface EMG recordings of the most involved limb in all positions were performed.Results: Postural tremor in addition to the rest one was found in 84% of the patients. The postural tremor was with lower amplitude than the rest one. The frequencies and EMG patterns of the postural tremors were different and correlated with some specific clinical symptoms. Patients with alternating postural tremor had a kinetic and intention tremor in addition.Conclusions: Four different subtypes of Parkinsonian tremor were found according to the presence and type of postural tremor. These subtypes had some differing clinical characteristics and probably different relationships to essential tremor.

Gabapentin for essential tremor: a multiple-dose, double-blind, placebo-controlled trial

Essential tremor (ET) is a common movement disorder that often becomes refractory to conventional pharmacologic management. Open-label studies suggest that gabapentin is efficacious for ET, but the results of controlled trials have been mixed. To determine the efficacy and tolerability of gabapentin in ET, we conducted a double-blind, placebo-controlled, cross-over trial evaluating two doses (1800 mg per day and 3600 mg per day; N = 25). Patients on other ET medications were maintained on their concurrent medications for 3 months prior to study initiation and throughout the study. Twenty patients (mean age, 69.9 +/- 6.1 yrs) completed the study. Overall, patient global assessments (p <0.05), observed tremor scores (p <0.005), water pouring scores (p <0.05), and activities of daily living scores (p <0.005) significantly improved. Accelerometry scores, spirographs, and investigator global impression scores did not improve. The results were similar for high and low doses. Statistical regression models did not demonstrate any significant predictors for response. Gabapentin may be effective in some cases of ET.

Clinical and electromyographic characteristics of tremor in patients with depression

The aim of this investigation was to establish the clinical and electromyographic pattern of tremor in patients with depression.Twenty-eight patients with depression and tremor and 30 patients with tremor and generalized anxiety disorder were investigated. Tremor was scored clinically by the Webster Tremor Scale. Electromyographic examination of tremor activity from antagonistic hand muscles was performed.Our results revealed in both groups of patients a postural and kinetic tremor with characteristics of an enhanced physiological tremor. Tremor involved only both upper limbs and no other body parts in all patients.In conclusion tremor in depression and generalized anxiety disorder is an enhanced physiological tremor.

Clinical and electromyographic examinations of patients with essential tremor

BACKGROUND

It is believed that no clinical differences exist among essential, familial and senile tremor, or between the tremor with synchronous or alternating electromyographic activity. The aim of this study was to evaluate the clinical and electromyographic findings in a large group of patients with different types of essential tremor.

METHODS

Two hundred and twenty patients with sporadic, familial or senile variants of essential tremor were examined. According to the electromyographic activity recorded from the antagonistic muscles, the patients were subdivided into a group with synchronous (SYN) and a group with alternating (ALT) activity. The historical aspects of the disease were noted, and a detailed neurological examination was performed.

RESULTS

A widespread tremor involving upper and lower limbs and 3-4 different anatomical regions was typical for familial tremor. It also had higher amplitude than the sporadic and senile tremor. ALT tremor had a higher amplitude and longer burst duration than SYN and more often involved lower limbs. Rest tremor was common in the ALT group. Overall, ALT tremor was more common than previously supposed.

CONCLUSION

The familial and ALT tremors are more disabling than other types of essential tremor. Since electromyographic ALT activity is common in essential tremor, its presence does not reliably distinguish essential and Parkinsonian tremor.

Essential Tremor

Multiple pharmacologic treatments have been studied, but propranolol and primidone have proven to be the most effective medications. It is unlikely that a patient will respond miraculously to another medication if his or her response to propranolol and primidone is minimal. Some subsets of essential tremor, however, such as the kinetic predominant type, may respond better to other medications. Mildly affected patients may not need treatment at all, and the potential benefits must always be weighed against the possible side effects. The main benefit of botulinum toxin injection is for head tremor, whereas its efficacy in hand tremor is variable. If a patient does not respond to adequate doses of propranolol or primidone, deep brain stimulation should be considered because it carries the lowest risk of the available surgical procedures; usually, it should be given preference over thalamotomy. It is important for the physician to realize the multitude of symptomatic treatments available. Beyond the conventional and often effective oral medications, use of newer treatments such as botulinum toxin, thalamotomy, and deep brain stimulation can often reduce tremor and lead to a greater quality of life for patients with ET.

Diurnal variation in tardive dyskinesia

Tardive dyskinesia (TD) is a common movement disorder that is associated with chronic neuroleptic exposure. To better characterize the clinical aspects of TD, we investigated the diurnal pattern of involuntary movements by blindly rating videotaped examinations of patients from the morning shortly after awakening and later in the same afternoon. In 10 patients, average TD ratings were worse in the afternoon than in the morning, especially in the case of limb-trunk dyskinesias. These findings suggest that it is important to rate patients at the same time of day in TD studies. Moreover, patients should be evaluated at least several hours after awakening.