Disorders of the central nervous system such as spasticity involve both neurological and muscular changes. In clinic, spasticity is routinely evaluated using the Ashworth scale and tendon reflex scale. In general, tendon reflexes have been widely used to evaluate neurological state and diagnose various neurological disorders including stroke, spinal cord injuries, multiple sclerosis, and cerebral palsy. However, although tendon reflexes have been recorded as part of the neurological examination for over a century, the evaluations have been mostly qualitative. The tendon reflex hammer used today is not much different from what was used more than a century ago. This history shows that the rubber-head tendon tapper meets the clinical need of quick and convenient evaluation. Yet it also indicates that there is potentially large room of improvement with more accurate and comprehensive measurements, which is especially useful in diagnosing pathological changes and evaluating treatment outcome. On the other hand, Ashworth scale measuring muscle responses to passive movement of a joint is also subjective, dependent on the evaluator's experience, and the scale is approximate on an ordinal scale. Considering that the tendon reflex evaluations can be extremely variable and may be misleading if used on their own, it could prove very useful if we could evaluate tendon reflexes and incorporate related muscle-joint assessment for more accurate and comprehensive evaluations. Great efforts have been made to develop sophisticated device to quantify tendon reflexes more accurately and to minimize the large variability involved. However, these studies are generally done in research labs and the tendon reflex evaluation devices used are not appropriate for a routine clinical setting. Accordingly, the goals of this study are to develop a pocket neuromuscular evaluator that delivers well-controlled tendon taps, makes accurate measurements of the taps and the reflex responses invoked. Furthermore, the device should also evaluate muscle-joint properties in terms of the natural frequency and damping ratio (equivalent to joint stiffness and viscous damping), and the optional muscle strength and joint ROM. Practically, the neuromuscular evaluator will be portable with the evaluation result displayed and recorded by the pocket device, making it suitable for quantitative evaluations of both neurological reflexes and muscle-joint properties and their changes associated with neurological impairments in a clinical setting. Considering the extremely wide use of the traditional reflex hammer in clinical practice and the combined quantitative evaluations of neurological and muscular properties provided by the proposed neuromuscular evaluator, its potential market is very large.
The proposed pocket neuromuscular evaluator will provide more accurate and comprehensive evaluations than the extremely widely used traditional reflex hammer. It will provide clinicians a quantitative and convenient tool to evaluate not only neurological reflexes but also the related muscle-joint properties, making the overall neuromuscular evaluations more accurate and reliable.