Abstract
Background The current classification of tremor types in Parkinson disease (PD) is potentially confusing, particularly for mixed tremor, and there is no label for pure resting tremor. With a view to better defining the clinical phenomenological classification of these tremors, our group relabeled the different types as follows: pure resting tremor (type I); mixed resting and action tremor with similar frequencies (type II) divided, according to action tremor presentation, into II-R when there is a time lag and II-C otherwise; pure action tremor (type III); and mixed resting and action tremor with differing frequencies (type IV). We performed a descriptive study to determine prevalence and clinical correlates for this new tremor classification. Patient/Methods A total of 315 consecutively recruited patients with PD and tremor were clinically evaluated. X2 tests were used to assess tremor type associations with categorical variables, namely, sex, family history of PD, motor fluctuations, and anticholinergic and beta-blocker use. With tremor type as the independent variable, ANOVA was performed to study the relationship between dependent quantitative variables, namely, age, age at PD diagnosis, disease duration, and UPDRS scores for rigidity. Results The studied patients had tremor types as follows: type I, 30%; type II, 50% (II-R, 25% and II-C, 25%); type III, 19%; and type IV, 1%. No significant association was found between the studied clinical variables and tremor types. Conclusions Mixed tremor was the most common tremor type in our series of patients with PD according to our proposed classification, which we hope will enhance understanding of the broad clinical phenomenology of PD.
Highlights
Tremor, one of the most characteristic manifestations of Parkinson disease (PD) and often the presenting sign, occurs in approximately 75% of patients with PD, who rank it as their second most troublesome symptom [1, 2].PD tremor, whether resting or action tremor, is a highly variable symptom [3]. e classical tremor is reported as a resting tremor of 4–7 Hz, often asymmetric, which ceases with volitional movement [4]
In 1998, the Consensus Statement on Tremor issued by the Movement Disorder Society (MDS) classified the different tremor types observed in PD in 3 categories: type I, resting and action tremor with similar frequencies; type II, resting and action tremor with differing frequencies; and type III, pure action tremor
Around 30% of patients had tremor type I, 50% had type II (25% II-R and 25% II-C), 19% had type III, and 1% had type IV
Summary
One of the most characteristic manifestations of Parkinson disease (PD) and often the presenting sign, occurs in approximately 75% of patients with PD, who rank it as their second most troublesome symptom [1, 2]. Action tremor, whether pure or mixed with resting tremor, is often observed in PD and has a reported prevalence of as high as 92% [5]. In 1998, the Consensus Statement on Tremor issued by the Movement Disorder Society (MDS) classified the different tremor types observed in PD in 3 categories: type I, resting and action tremor with similar frequencies; type II, resting and action tremor with differing frequencies; and type III, pure action tremor. A more recent revised Consensus Statement does not modify the tremor type classification for PD [7]. In our opinion, this classification has led to some confusion regarding mixed tremor.
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