Toward quantitative characterization of essential tremor for future tremor suppression.

Tremor is the most common movement deficit and manifests in a variety of disorders, including Essential Tremor, Parkinson's Disease, Dystonia, and Cerebellar Ataxia. Although medication and surgical interventions have significantly reduced patient suffering, they are only partially effective and can carry undesired side effects, leaving many patients without satisfactory treatment options. Wearable tremor-suppressing devices could provide an alternative to medication and surgery. Multiple research groups have developed orthotic prototypes to low-pass filter tremor, but these devices have not yet been optimized for in-vivo use. Optimizing non-invasive tremor suppression requires an understanding of where the tremor originates mechanically (which muscles) and how it propagates to the hand (where it matters most). Here we present on the beginnings of our multi-pronged work to determine the origin, propagation, and distribution of Essential Tremor, and we provide preliminary results.

Immediate electromyographic changes of the upper limb muscles following cervical manipulation in a patient with essential tremor: a case report / Alterações eletromiográficas imediatas dos músculos dos membros superiores após manipulação cervical em uma paciente com tremor essencial: estudo de caso

Introduction and Objective: The purpose of this case report is to evaluate upper limb muscle electric behavior by surface electromyography before and after cervical manipulation in a patient with essential tremor. Methods: In 2009, essential tremor was diagnosed by a neurologist in a 25-year-old woman. Previous treatment included Paroxetine for a number of months, without alteration of her symptoms. The patient was assessed by surface electromyography of the upper limb muscles (flexor and extensor of the wrist, long heads of biceps and triceps) before and after being subjected to high-velocity, low-amplitude spinal manipulation to her mid cervical spine (C3-C4 level, 1 manipulation/side). Results: There was an increase of the median frequency rate and a decrease of the electrical activity of these muscles. Conclusion: This case study showed the cervical manipulation technique acutely modifying the electromyographic activity, increasing the median frequency, and decreasing the muscle recruitment of the upper limb. It suggests improved motor control during the tasks.

Introdução e Objetivo: O objetivo neste estudo de caso foi avaliar o comportamento elétrico dos músculos do membro superior, por eletromiografia, antes e após manipulação cervical em paciente com tremor essencial. Métodos: Uma mulher (25 anos) apresentou-se com tremor essencial, diagnosticado em 2009 por neurologista. Foi empregado tratamento prévio com Paroxetina por meses, sem diminuição dos sintomas. A paciente foi avaliada por eletromiografia dos músculos dos membros superiores (flexores e extensores do punho, cabeça longa do bíceps e do tríceps) antes e após manipulação de alta velocidade e baixa amplitude na cervical média (nível C3-C4, 1 manipulação para cada lado). Resultados: Observou-se aumento na frequência mediana e diminuição na atividade elétrica dos músculos avaliados. Conclusão: A técnica de manipulação cervical modificou de forma imediata a atividade eletromiográfica, aumentando a frequência mediana e diminuindo o recrutamento dos músculos do membro superior para a paciente estudada, sugerindo melhor controle motor durante a atividade proposta.

Validity of a screening question for head tremor: an analysis of four essential tremor case samples.

BACKGROUND: The goal of this study was to assess the validity of a screening question for head tremor in essential tremor (ET). There are no published data on this topic, and the knowledge will guide future epidemiological investigations of this disorder. METHODS: These analyses utilized four distinct patient samples: a population-based study in northern Manhattan, a study of the environmental epidemiology of ET, a genetics study, and a brain repository. Sensitivity was the proportion of ET cases with head tremor on examination who self-reported head tremor. RESULTS: The sensitivity of the screening question for head tremor was lowest in the population-based study (31.6%), and higher as well as somewhat similar across the remaining studies (46.7 to 62.2%). Higher sensitivity was associated with tremor of longer duration, presence of voice tremor on examination, female gender, and lower education. The use of the screening question would have increased case ascertainment during the screening phase of these four studies by 1.9, 4.1, 10.2, and 20.3%. CONCLUSIONS: A screening question for head tremor had low-to-moderate sensitivity in ET. The use of such a screening questionnaire, however, has the potential to increase case ascertainment by as much as 20% in some screening settings.

Wine drinking and essential tremor: a possible protective role.

The purpose of this study was to evaluate the possible association of cigarette smoking, coffee drinking, and wine consumption with essential tremor using a matched case-control design. Cases and controls were enrolled from 6 Movement Disorder centers in central-southern Italy. Essential tremor was diagnosed according to Bain's criteria. Three unrelated healthy controls (not affected by neurological disorders) per each enrolled case, matched by sex and age (± 5 years), were selected. A standardized questionnaire was administered to record demographic, epidemiological, and clinical data. All cases and controls underwent a standard neurological examination. Adjusted odds ratios and 95% confidence intervals were estimated using conditional logistic regression for the matched cases and controls. Eighty-three patients with essential tremor (38 men and 45 women; mean age, 68.2 ± 8.6 years) and 245 matched control subjects (113 men and 132 women; mean age, 68.4 ± 9.7 years) were enrolled in the study. Multivariate analysis showed a significant negative association between essential tremor and wine consumption preceding the onset of disease (adjusted odds ratio, 0.23; 95% confidence interval, 0.08-0.64; P = .0005) with a significant dose effect (1-2 glass of wine per day: odds ratio, 0.32; 95% confidence interval, 0.10-0.95; P = .04; more than 3 glass of wine per day: odds ratio, 0.14; 95% confidence interval, 0.03-0.62; P = .01). In our sample no association between essential tremor and cigarette smoking or coffee drinking was found. Our data suggest a negative association between wine drinking and essential tremor, which could be explained by the long-term neuroprotective effect of its antioxidant components.

Antihypertensive agents and risk of Parkinson's disease, essential tremor and dementia: a population-based prospective study (NEDICES).

BACKGROUND: Recent interest in antihypertensive agents, especially calcium channel blockers, has been sparked by the notion that these medications may be neuroprotective. A modest literature, with mixed results, has examined whether these medications might lower the odds or risk of Parkinson's disease (PD) or dementia. There are no data for essential tremor (ET). OBJECTIVE: To examine the association between antihypertensive use (defined broadly and by individual subclasses) and ET, PD and dementia. For each disorder, we used cross-sectional data (association with prevalent disease) and prospective data (association with incident disease). METHODS: Prospective population-based study in Spain enrolling 5,278 participants at baseline. RESULTS: Use of antihypertensive medications (aside from beta-blockers) was similar in prevalent ET cases and controls. Baseline use of antihypertensive agents was not associated with reduced risk of incident ET. Antihypertensive medication use was not associated with prevalent or incident PD. Calcium channel blocker use was marginally reduced in prevalent dementia cases (OR(adjusted) = 0.63, p = 0.06) but was not associated with reduced risk of incident dementia (RR(adjusted) = 1.02, p = 0.95). CONCLUSIONS: We did not find evidence of a protective effect of antihypertensive medications in these three neurodegenerative disorders.

Lacosamide, the new anticonvulsant, effectively reduces harmaline-induced tremors in rats.

The present study aimed at evaluating the efficacy of lacosamide (0.3 to 30 mg/kg), a new anticonvulsant drug, in a model of essential tremor in comparison to the reference compounds propranolol and primidone. We observed a high tremorlytic effect of lacosamide reducing the intensity of tremors following harmaline administration in a dose-dependent manner. The highest dose also modified the latency and intensity of tremor at onset. The effect of lacosamide was equal or even superior to propranolol and primidone indicating that lacosamide may be a new antitremorgenic drug that merits further clinical investigation.

Mandibular physiological tremor is reduced by increasing-force ramp contractions and periodontal anaesthesia.

We have previously shown that the application of anaesthesia to periodontal mechanoreceptors (PMRs) dramatically reduces the 6-12 Hz physiological tremor (PT) in the human mandible during constant isometric contractions where visual feedback is provided. This current study shows that during a ramp contraction where force is slowly increased, the amplitude of mandibular PT is almost five times smaller on average than when the same force ramp is performed in reverse, i.e. force is slowly decreased. This smaller tremor is associated with a higher mean firing rate of motor units (MUs) as measured by the sub-30 Hz peak in the multi-unit power spectrum. The decrease in the amplitude of PT following PMR anaesthetisation is associated in some instances with a similar increase in the overall firing rate; however this change does not match the diminution of tremor. The authors postulate that the decrease in mandibular PT during increasing force ramps may be due to a change in the mean firing rate of the MUs. The change in tremor seen during PMR anaesthetisation may in part be due to a similar mechanism; however other factors must also contribute to this.

Mediterranean diet and essential tremor. A case-control study.

BACKGROUND: Higher adherence to the Mediterranean diet (MeDi) has been related to lower Alzheimer's disease risk. Some dietary factors have been studied in patients with essential tremor (ET), but the MeDi's effect has not been investigated. METHODS: Adherence to the MeDi was calculated from a food frequency questionnaire administered in a case-control study of environmental epidemiology of ET in the New York Tri-State area. Logistic regression models were used to examine whether adherence to the MeDi predicted ET (vs. control) outcome. The models adjusted for age, gender, ethnicity, education, caloric intake, body mass index, smoking, ethanol consumption, coffee intake and blood harmane concentrations. RESULTS: 148 ET cases adhered less to MeDi (0-9 scale with higher scores indicating higher adherence) than 250 controls (mean 4.3 +/- 1.7 vs. 4.7 +/- 1.7; p = 0.03). Higher adherence to MeDi was associated with lower odds for ET [0.78 (0.61-0.99); p = 0.042]. As compared to subjects at the lowest MeDi adherence tertile, those at the middle tertile had lower ET odds [0.41 (0.16-1.05)], while subjects at the highest tertile had an even lower ET odds [0.29 (0.10-0.82); p for trend 0.021]. CONCLUSIONS: Compared to controls, ET cases adhered less to MeDi. The gradual reduction in ET odds with higher MeDi adherence tertiles suggests a possible dose-response effect. The mechanisms that underlie this association merit further study.

Disappearance of essential tremor after frontal cortical infarct.

We present a patient with essential tremor who spontaneously improved after a sensorimotor stroke related to a small cortical infarct near by the left precentral region of the brain. This finding supports the presence of cortical or transcortical motor loops that are likely involved in essential tremor and suggests a possible link with the cerebellar-thalamic-cortical pathway.

Voluntary control and a wider clinical spectrum of essential palatal tremor.

Essential palatal tremor (EPT) may not be a uniform or single entity. We present two patients who had some "voluntary control" over EPT, including entrainment. We review the English language literature on EPT to describe a wider clinical spectrum of this syndrome.

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.