Target board test for the quantification of ataxia in tremulous patients

The objective was to develop and assess the validity and reliability of a target board test (TBT) for quantifying ataxia and measuring dysmetria in the presence of tremor.

Each subject was instructed to reach out and mark a target placed at arm's length with a pen (10 times with each hand). Ten patients performed the test twice.

A hospital-based multiple sclerosis (MS) unit.

Fifty-three patients with MS and upper limb tremor/ataxia and 20 healthy control subjects. The MS patients were classified into four subgroups: MS control group (n = 13), MS tremor group (n = 9), MS dysmetria group (n = 6), MS mixed (tremor and dysmetria) group (n = 25).

The main outcome measures were the average radial distance away from the target (mean R) and the mean directional error (mean V) of the 10 contact points from the target. From these a dysmetria tremor index (DTI) was calculated by dividing mean V by mean R. Also used were a dysmetria scale, a dysdiadochokinesia scale and a finger-tapping test.

Mean R correlated significantly with dysmetria, dysdiadochokinesia, kinetic tremor and (inversely) with the finger-tapping test (all p < 0.005). The median difference between two measurements of mean R for all 10 contact points was 11.3% and 19.0% and for mean V48.3% and 63.4% and DTI 57.2% and 50.5% for the right- and left-hand sides respectively, indicating the considerable directional variability within ataxia.

The TBT provides simple quantitative objective measurements of upper limb ataxia.