Validation of a portable instrument for assessing tremor severity in epidemiologic field studies

Louis, Elan D.; Yousefzadeh, Edna; Barnes, Livia F.; Yu, Qiping; Pullman, Seth L.; Wendt, Kristin J.

doi:10.1002/1531-8257(200001)15:1<95::aid-mds1015>3.0.co;2-d

Cited by 40 publications

(25 citation statements)

References 21 publications

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“…The nine-hole test alone has been used extensively for evaluation of Mn-related dynamic tremor (Bouchard et al, 2005, 2007a; Mergler et al, 1994). The combination of nine-hole and groove-type tests were used to quantify essential tremor (Louis et al, 2000) and kinetic tremor associated with smoking (Louis, 2007). The Benton visual retention test measures visual perception and nonverbal short-term memory and has been used to evaluate normal memory loss in elderly subjects (Larrabee and Crook, 1994; Seo et al, 2007), pathological memory loss in Alzheimer’s and dementia patients (Ferman et al, 2006; Kawas et al, 2003), and neurological function of Mn-exposed welders and ferroalloy plant workers (Bast-Pattersen et al, 2004; Wang et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Manganese exposure among smelting workers: Relationship between blood manganese–iron ratio and early onset neurobehavioral alterations

et al. 2009

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A biomarker for detection of early onset neurobehavioral alterations in manganism remains unknown. The purpose of this study was to use a neurobehavioral test battery to identify subtle changes in Mn-induced motor and memory dysfunction and to relate the quantifiable neurological dysfunction to an established Mn-exposure index such as blood manganese–iron ratio (MIR). A total of 323 subjects were recruited to control (n = 106), low-exposure (122), and high-exposure (95) groups. The test battery consisted of standard testing procedures including the nine-hole and groove-type steadiness tester, Benton visual retention test, and Purdue pegboard coordination test. No significant health problems or clinically diagnosed neurological dysfunctions were observed. Benton test did not reveal any abnormal memory deficits among Mn-exposed smelters, nor did the groove and nine-hole tests detect any abnormality in dynamic and static steadiness in tested subjects. Purdue pegboard test showed a remarkable age-related decline in fine movement coordination among all study participants regardless of the Mn-exposure condition. Mn exposure significantly exacerbated this age-related deterioration. Statistical modeling revealed that the plasma and erythrocyte MIR (i.e., pMIR and eMIR, respectively) were associated with Purdue pegboard scores. Among all subjects whose MIR were above the cut-off value (COV), pMIR was significantly correlated with pegboard scores (r = −0.261, p = 0.002), whereas for those subjects over the age of 40, the eMIR, but not pMIR, was associated with declined pegboard performance (r = −0.219, p = 0.069). When both factors were taken into account (i.e., age > 40 and MIR > the COV), only pMIR was inversely associated with pegboard scores. Combining their usefulness in Mn-exposure assessment, we recommend that the blood Mn–Fe ratio may serve as a reasonable biomarker not only for assessment of Mn exposure but also for health risk assessment.

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Section: Introductionmentioning

confidence: 99%

Manganese exposure among smelting workers: Relationship between blood manganese–iron ratio and early onset neurobehavioral alterations

et al. 2009

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“…Bender visual-motor gestalt test (BGT) (Kishi et al 1993), and Benton visual retention test (B-VRT) (Mathiesen et al 1999; Bast-Pettersen et al 2005). The results of static steadiness, aiming, and tracking/drawing tests have been used to classify tremor respectively as postural, intention, or kinetic (Louis et al 2000;Louis 2007; Buijink et al 2012; National Institute of Neurological Disorders and Stroke 2012; Gonzalez-Usigli & Espay 2013; Sternberg et al 2013). …”

Section: Resultsmentioning

confidence: 99%

Persistence of mercury-induced motor and sensory neurotoxicity: systematic review of workers previously exposed to mercury vapor

Fields¹,

Borak

Louis

2017

Critical Reviews in Toxicology

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Background Elemental mercury (Hg0) is a well-recognized neurotoxicant, but it is uncertain whether and for how long its neurotoxicity persists. Among studies that evaluated previously-exposed workers, only one examined workers during and also years after exposure had ceased. Objective To create a series of ‘synthetic’ longitudinal studies to address the question of persistence of Hg0 neurotoxicity in occupationally exposed workers. Methods We systematically reviewed studies describing objective motor and sensory effects in previously-exposed mercury workers. Data from physical examination (PE), neurobehavioral (NB) tests and electrophysiological studies were extracted into structured tables and examined for their consistency and dose-relatedness and then compared with the corresponding results from studies of currently-exposed workers. Results We identified six cohorts that described neurological findings in 1299 workers, examined an average of 4.8 to 30 years after the cessation of exposure. Historical group mean UHg levels ranged from 23 to >500 μg/L, with UHg levels >6000 μg/L in some individuals. Overall, few findings were significant; most were inconsistent across the remote-exposure studies, and in comparisons between studies of remotely- and currently-exposed workers. Conclusion The results of this systematic review indicate that Hg0-related neurotoxic effects detectable on PE, NB testing, and EPS are substantially reversed over time. To the extent that such effects do persist, they are reported principally in workers who have had very high dose exposures. In addition, based on limited available data, those effects reported to persist have been described as having little or no functional significance.

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“…Bender visual-motor gestalt test (BGT), and Benton visual retention test (B-VRT). Outcomes on tests of static steadiness, aiming, and tracking/drawing have been used to classify tremor as postural, intention, or kinetic, respectively (Louis et al 2000; Louis 2007; Buijink et al 2012; NINDS 2012; Gonzalez-Usigli & Espay 2013; Sternberg et al 2013). …”

Section: Methodsmentioning

confidence: 99%

Mercury-induced motor and sensory neurotoxicity: systematic review of workers currently exposed to mercury vapor

Fields¹,

Borak

Louis

2017

Critical Reviews in Toxicology

Self Cite

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Background The neurotoxicity of elemental mercury (Hg0) is well-recognized, but it is uncertain whether and for how long neurotoxicity persists; among studies that evaluated previously exposed workers, only one examined workers during and also years after exposure ceased. Objective To document the type, frequency, and dose-relatedness of objective neurological effects in currently exposed mercury workers and thereby provide first approximations of the effects one would have expected in previously exposed workers evaluated during exposure. Methods We systematically reviewed studies of neurotoxicity in currently exposed mercury workers identified by searching MEDLINE (1950 –2015), government reports, textbook chapters, and references cited therein; dental cohorts were not included. Outcomes on physical examination (PE), neurobehavioral (NB) tests and electrophysiological studies were extracted and evaluated for consistency and dose-relatedness. Results Forty-five eligible studies were identified, comprising over 3000 workers chronically exposed to a range of Hg0 concentrations (0.002 to 1.7 mg/m3). Effects that demonstrated consistency across studies and increased frequency across urine mercury levels (<50; 50–100; 100–200; ≥ 200 µg/L) included tremor, impaired coordination, and abnormal reflexes on PE, and reduced performance on NB tests of tremor, manual dexterity and motor speed. The data suggest response thresholds of UHg ≈275 µg/L for PE findings and ≈20 µg/L for NB outcomes. Conclusion These results indicate that PE is of particular value for assessing workers with UHg > 200 µg/L, while NB testing is more appropriate for those with lower UHg levels. They also provide benchmarks to which findings in workers with historical exposure can be compared.

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Validation of a portable instrument for assessing tremor severity in epidemiologic field studies

Cited by 40 publications

References 21 publications

Manganese exposure among smelting workers: Relationship between blood manganese–iron ratio and early onset neurobehavioral alterations

Manganese exposure among smelting workers: Relationship between blood manganese–iron ratio and early onset neurobehavioral alterations

Persistence of mercury-induced motor and sensory neurotoxicity: systematic review of workers previously exposed to mercury vapor

Mercury-induced motor and sensory neurotoxicity: systematic review of workers currently exposed to mercury vapor

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