Relationships between quantitative measures and neurologist's clinical rating of tremor and standing steadiness in two epidemiological studies

Objective. The purpose of the present investigation was to 1) compare a neu rologist's physical examination (NPx) rating of severity of postural tremor to several summary measures derived from quantitative measurements of trem or and 2) compare a NPx rating of standing steadiness and related clinical findings to quantitative sway speed measurements. Methods. Comparisons were performed on data obtained from two epidemiologic al field studies: I) retired heavy industrial workers (n=198, approximately half previously exposed to elemental mercury), and 2) small town residents (n=234, approximately 40% with environmental exposure to arsenic). A comme rcially available tremor measurement instrument was used in both studies. T o obtain standing steadiness measures, a head position monitoring device wa s used in the mercury study, and a force platform was used in the arsenic s tudy. The NPx included assessment of postural tremor as well as evaluation of vibration perception and proprioception of the great toe, Achilles tendo n reflex activity, Romberg test status, and tandem gait. One neurologist pe rformed all the NPx in both studies and results were graded as normal, equi vocal, or abnormal. The square root of the proportion of variance accounted for by a linear trend term in ANOVA models was used as an estimate of asso ciation between quantitative tests and clinical examination grade. An estim ate of agreement, kappa, was also calculated after both NPx and quantitativ e test results were dichotomized. Results. Most tremor summary measures varied monotonically with NPx tremor severity grade. Moderately good associations were observed between the trem or acceleration measure and NPx postural tremor grade (correlations up to s imilar to0.5). Sway speed with eyes open and with eyes closed increased mon otonically with NPx grade for most of the clinical signs. The NPx signs sho wing the strongest relationships with sway speed were Romberg rest performa nce, tandem gait, and proprioception and vibration sensation of the great t oe (correlations up to similar to0.5). Conclusions. Quantitative tremor measurements were related to a neurologist 's grading of postural tremor. Sway speed was associated with several NPx f indings related to standing stability. Quantitative measurements of tremor and standing stability may provide more precise and objective measures of n eurological function than NPx by a neurologist and are likely to De more co nsistent across times and examiners. (C) 2000 Inter Press, Inc.