Outcome measures of spasticity

Spasticity is characterized by a velocity-dependent increase in muscle resistance, in response to a passive stretch. Whilst clinical scales probably represent the most common approach to its measurement, these are limited by poor reliability and difficulties with some definitions. However, recently, a simple system has been used to provide the clinician with a measure of the force applied during the Ashworth Test. The Wartenberg Pendulum Test has been devised for measuring spasticity at the knee, but has been shown to be unsuitable for measuring more severe spasticity. Powered systems have been used in research studies, but are rarely considered suitable for routine clinical use. However, one method of interest, using a low inertia torque motor to measuring stiffness at the wrist, has been shown to provide rapid measurements which correspond to the degree of spasticity defined by other scales. Clinical gait analysis may have an important role to play in assessing spasticity - since there are clear associations between lower limb spasticity and gait problems - but it does not provide a true measure of the condition. In summary, while scales remain the most common method of measuring spasticity, there is considerable potential in instrumented techniques that can provide greater reliability and precision of measurement.