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      The Non-motor Features of Essential Tremor: A Primary Disease Feature or Just a Secondary Phenomenon?

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          Abstract

          Essential tremor (ET) is a pathologically heterogeneous neurodegenerative disorder with both motor and increasingly recognized non-motor features. It is debated whether the non-motor manifestations in ET result from widespread neurodegeneration or are merely secondary to impaired motor functions and decreased quality of life due to tremor. It is important to review these features to determine how to best treat the non-motor symptoms of patients and to understand the basic pathophysiology of the disease and develop appropriate pharmacotherapies. In this review, retrospective and prospective clinical studies were critically analyzed to identify possible correlations between the severities of non-motor features and tremor. We speculated that if such a correlation existed, the non-motor features were likely to be secondary to tremor. According to the current literature, the deficits in executive function, attention, concentration, and memory often observed in ET are likely to be a primary manifestation of the disease. It has also been documented that patients with ET often exhibit characteristic personality traits. However, it remains to be determined whether the other non-motor features often seen in ET, such as anxiety, depression, and sleep disturbances are primary or secondary to motor manifestations of ET and subsequent poor quality of life. Finally, there is evidence that patients with ET can also have impaired color vision, disturbances of olfaction, and hearing impairments, though there are few studies in these areas. Further investigations of large cohorts of patients with ET are required to understand the prevalence, nature, and true significance of the non-motor features in ET.

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          Most cited references47

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          Correlates of functional disability in essential tremor.

          The decision to treat patients with essential tremor (ET) is based primarily on the functional impact of the tremor. Correlates of functional disability, apart from the severity of the tremor itself, have not been studied. The objective of this work was to study correlates of functional disability in ET, and to present data on the extent of functional disability in community-dwelling ET cases. ET cases and age-matched control subjects were ascertained from a tertiary referral center at Columbia-Presbyterian Medical Center and a community in northern Manhattan, N.Y. Subjects underwent a 2.5-hour evaluation, including a tremor disability questionnaire, a videotaped tremor examination rated by a neurologist, a performance-based test of function, quantitative computerized tremor analysis, the Hamilton Anxiety Rating Scale, and the depression module of the Structured Clinical Interview for DSM-IV. Seventy-six (85.4%) of 89 cases reported disability on > or =1 item on the disability questionnaire. In multivariate linear regression analyses, current major depression, Hamilton Anxiety Rating Scale score, age, and tremor severity were independently correlated with performance-based test scores. Twenty-seven (73.0%) of 37 community cases reported disability on > or =1 (mean = 8.4) item on the questionnaire, and 25 (67.6%) demonstrated moderate or greater difficulty on > or =1 (mean = 4.2) task in a performance-based test. Depression, anxiety, and age, independent of the severity of tremor, were associated with greater functional disability in ET, so that these factors must be considered when assessing the impact of new treatments in ET. Among a group of community-dwelling cases, approximately three-quarters reported disability, suggesting that the number of individuals who might receive some benefit from advances in the treatment of ET is probably a great deal larger than previously thought. Copyright 2001 Movement Disorder Society.
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            Population-based case-control study of cognitive function in essential tremor.

            To determine whether patients with essential tremor (ET) have cognitive deficits when compared with controls and whether the types of cognitive deficits reported previously are also found in this large sampling of patients with ET. A total of 232 patients with ET and 696 matched controls age 65 years or older (median 75 years) living in central Spain (the Neurologic Diseases in Central Spain study) underwent a neuropsychological assessment, including tests of global cognitive performance, frontal executive function, verbal fluency, and memory. Subjects also were asked whether they had forgetfulness. Fifty-six patients with ET were previously undiagnosed; only 14 (6%) were taking medication for tremor. Adjusted for age, gender, education, premorbid intelligence, medications, and depressive symptoms, cases performed less well on most neuropsychological tests and especially tests of global cognitive performance (37-item Mini-Mental State Examination = 27.0 +/- 6.7 in cases vs 28.9 +/- 5.9 in controls, p < 0.001) and frontal executive function (Trail Making Test number of errors = 8.7 +/- 11.0 in cases vs 3.8 +/- 7.6 in controls, p < 0.001). Forgetfulness was reported in 117 (50.4%) patients with ET vs 300 (43.1%) controls (p = 0.05). In a population-based sample of largely untreated patients with essential tremor, cases performed more poorly on formal neuropsychological testing than did their counterparts without tremor. A complaint of forgetfulness was also marginally more common in patients with essential tremor.
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              Incidence of essential tremor in three elderly populations of central Spain.

              To estimate the incidence of essential tremor (ET) in three populations in central Spain using data from the Neurologic Disorders in Central Spain (NEDICES), a population-based survey of elderly subjects (65 years and older). Individuals were evaluated at baseline (1994 to 1995) and at follow-up (a median of 3.3 years later in 1997 to 1998). The evaluation included a screening question for ET and a neurologic examination, when possible. Of 5,278 subjects evaluated at baseline, there were 256 prevalent ET cases. Eighty-three incident ET cases were identified among 3,942 individuals assessed at follow-up. The adjusted annual incidence rate (per 100,000 person-years) in the population aged 65 years and older was 616 (95% CI: 447 to 784). Sixty-four (77.1%) of 83 incident cases had not been diagnosed before our assessment. The incidence of ET may be higher than previously recognized because a large proportion of patients with ET may never seek medical attention.
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                Author and article information

                Journal
                Tremor Other Hyperkinet Mov (N Y)
                Tremor Other Hyperkinet Mov (N Y)
                TOHM
                Tremor and Other Hyperkinetic Movements
                Columbia University Libraries/Information Services
                2160-8288
                2014
                5 August 2014
                : 4
                : 255
                Affiliations
                [1]Department of Neurology, National Institute of Mental Health & Neurosciences, Bangalore-560029, Karnataka, India
                Columbia University, USA
                Author notes
                *To whom correspondence should be addressed. E-mail: pal.pramod@ 123456rediffmail.com
                Article
                10.7916/D8D798MZ
                4122824
                25120945
                e0a95145-2f50-4582-80b0-508dfd570aff
                Copyright @ 2014

                This is an open-access article distributed under the terms of the Creative Commons Attribution–Noncommerical–No Derivatives License, which permits the user to copy, distribute, and transmit the work provided that the original author and source are credited; that no commercial use is made of the work; and that the work is not altered or transformed.

                History
                : 22 May 2014
                : 6 July 2014
                Page count
                Pages: 12
                Categories
                Reviews

                non-motor features,tremor,essential tremor,cognition,depression,anxiety

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