Computerized measurement of motor performance after stroke

Stroke scales usually convert motor status to a score along an ordinal scale and do not provide a permanent recording of motor performance. Computerized methods sensitive to small changes in neurological status may be of value for studying and measuring stroke recovery.

We developed a computerized dynamometer and tested 23 stroke subjects and 12 elderly control subjects on three motor tasks: sustained squeezing, repetitive squeezing, and index finger tapping. For each subject, scores on the Fugl-Meyer and National Institutes of Health stroke scales were also obtained.

Sustained squeezing by the paretic hand of stroke subjects was weaker (9.2 kg) than the unaffected hand (20.2 kg; P < .0005), as well as control dominant (23.1 kg; P < .0005) and nondominant (19.9 kg; P < .005) hands. Paretic index finger tapping was slower (2.5 Hz) than the unaffected hand (4.2 Hz; P < .01), as well as control dominant (4.7 Hz; P < .0005) and nondominant (4.9 Hz; P < .0005) hands. Many features of dynamometer data correlated significantly with stroke subjects' Fugl-Meyer scores, including sustained squeeze maximum force (rho = .91) and integral of force over 5 seconds (rho = .91); repetitive squeeze mean force (rho = .92) and mean frequency (rho = .73); and index finger tap mean frequency (rho = .83). Correlation of these motor parameters with National Institutes of Health stroke scale score was weaker in all cases, a consequence of the scoring of nonmotor deficits on this scale. Dynamometer measurements showed excellent interrater (r = .99) and intrarater (r = .97) reliability.

The degree of motor deficit quantitated with the dynamometer is strongly associated with the extent of neurological abnormality measured with the use of two standardized stroke scales. The computerized dynamometer rapidly measures motor function along a continuous, linear scale and produces a permanent recording of hand motor performance accessible for subsequent analyses.