Impaired touch discrimination after stroke: A quantitative test

The ability to discriminate differences in tactile stimuli, such as textures, is commonly and characteristically impaired after stroke. Assessment. of tactile discrimination is currently compromised by measures that are not quantitative and standardized, do not assess active touch sensibility or are not suitable for use in clinical settings with stroke patients. Therefore, a test that addressed these limitations was developed. The Tactile Discrimination Test required subjects to discriminate differences in finely graded plastic ridged surfaces using a three-alternative forced choice design. Test-retest reliability, based on a sample of 35 stroke patients, was high (r = 0.92), and changes of the magnitude of 27 percent spatial increase (PSI) can be detected with 95 percent confidence, which is sufficiently accurate for clinical monitoring. A matched pairs study of 50 stroke and 50 unimpaired subjects found that normal performance scores were contained within the 3-46 PSI range. The conservative criterion of abnormality was defined as 46 PSI, with a zone of uncertainty from 31 to 61 PSI. The test differentiated well impaired performance relative to normal standards. These results support the application of the Tactile Discrimination Test as a quantitative, standardized measure appropriate for testing stroke patients in clinical settings.