Prevalence and characteristics of tremor in the NARCOMS multiple sclerosis registry: a cross-sectional survey

Abstract

Objectives: (1)To describe the prevalence and severity of tremor in patients with multiple sclerosis (MS) registered within a large North American MS registry; (2) to provide detailed descriptions on the characteristics and severity of tremor in a subset of registrants and (3) to compare several measures of tremor severity for strength of agreement.

Setting: The North American Research Committee on MS (NARCOMS) registry.

Participants: Registrants of NARCOMS reporting mild or greater tremor severity.

Outcome measures: We determined the cross-sectional prevalence of tremor in the NARCOMS registry over three semiannual updates between fall 2010 and fall 2011. A subset of registrants (n=552) completed a supplemental survey providing detailed descriptions of their tremor. Outcomes included descriptive characteristics of their tremors and correlations between outcome measures to determine the strength of agreement in assessing tremor severity.

Results: The estimated prevalence of tremor in NARCOMS ranged from 45% to 46.8%, with severe tremor affecting 5.5-5.9% of respondents. In the subset completing the supplemental survey, mild tremor severity was associated with younger age of MS diagnosis and tremor onset than those with moderate or severe tremor. However, tremor severity did not differ by duration of disease or tremor. Respondents provided descriptions of tremor symptoms on the Clinical Ataxia Rating Scale, which had a moderate to good (ρ=0.595) correlation with the Tremor Related Activities of Daily Living (TRADL) scale. Objectively scored Archimedes' spirals had a weaker (ρ=0.358) correlation with the TRADL. Rates of unemployment, disability and symptomatic medication use increased with tremor severity, but were high even among those with mild tremor.

Conclusions: Tremor is common among NARCOMS registrants and severely disabling for some. Both ADL-based and symptom-descriptive measures of tremor severity can be used to stratify patients.

Keywords: EPIDEMIOLOGY.

Figure 1

Recruitment flowchart. The upper bracket depicts how tremor prevalence was determined for the NARCOMS registry over three consecutive semi-annual surveys in fall 2010, spring 2011 and fall 2011. The lower bracket depicts the derivation of the Surveyed Cohort from those registrants with mild or worse tremor who were mailed the supplemental survey. NARCOMS, North American Research Committee on Multiple Sclerosis; TACS, Tremor and Coordination Scale.

Figure 2

Bodily distribution of tremor among surveyed registrants. The figure depicts the number (%) of patients reporting tremor in each of 7 bodily regions. The table reports the proportion of respondents indicating tremor in either or both upper or lower extremities, and the occurrence of tremor in the dominant versus non-dominant arm. The histogram depicts how the tremor was distributed throughout the body for respondents with at least mild tremor.

Figure 3

Employment, disability and symptomatic medication use by tremor severity. The figure depicts the proportion of registrants indicating unemployment, disability status and use of symptomatic medication by two different measures of tremor severity. The upper figure depicts tremor severity by the Tremor and Coordination Scale (TACS) scores derived from the North American Research Committee on Multiple Sclerosis (NARCOMS) semiannual updates. The scores denote mild (TACS=2), moderate (TACS=3), severe (TACS=4) and totally disabling (TACS=5) tremor. The lower figure depicts tremor severity by dividing responses on the Tremor Related Activities of Daily Living scale into quartiles of severity ranging from 1 (least severe) to 4 (most severe).