Portable device for quantifying parkinsonian wrist rigidity.

The need for objectivity in the assessment of parkinsonism prompted the development of a portable transducer capable of quantifying muscular rigidity. This paper describes the development and use of a device for measuring wrist rigidity and reports the preliminary findings from 25 normal healthy controls and 29 patients, many of whom were undergoing antiparkinsonian treatment to alleviate rigidity or antipsychotic treatment, which produced parkinsonian rigidity. An objective rigidity score, representing the degree to which motor activity increases muscular stiffness in the wrist, correlates highly with clinical ratings of parkinsonian rigidity and demonstrates 89% specificity and 82% sensitivity. Unlike previous techniques for quantifying rigidity, this transducer offers greater portability and apparent face validity.