Tonic stretch reflex threshold as a measure of spasticity: implications for clinical practice.
Lance's definition of spasticity states: (1) the excitability of the tonic stretch reflex threshold is the conceptual unit of measure of spasticity; (2) because spasticity is a velocity-dependent phenomenon, different velocities of stretch should be used to evaluate spasticity; and (3) measures should provide insight into the role of spasticity in disordered motor control. This article reviews studies of clinical and laboratory-based methods to evaluate spasticity. There is a lack of consensus regarding the conceptual unit that best captures spasticity. Several biomechanical variables and parameters such as stretch reflex gain, stretch reflex threshold, and/or suprathreshold phenomena are often measured alone or in combination without a unifying conceptual framework. Most studies do not establish links between spasticity and other motor deficits and adhere only partly to Lance's definition. A promising alternative to current measures is offered by the lambda model that uses the tonic stretch reflex threshold as the descriptor of spasticity. The lambda model also provides a framework in which spasticity and the presence of disorders in muscle activation can be described and explained. We introduce a portable device to measure spasticity, based on the measurement of the tonic stretch reflex threshold, which is more closely related to Lance's definition.
Calota
Andra
A
School of Physical and Occupational Therapy, McGill University, Montreal, Quebec, Canada.
Levin
Mindy F
MF
D001696:Biomechanical Phenomena; D004576:Electromyography / Q000295:instrumentation*; D006801:Humans; D009128:Muscle Spasticity / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D009129:Muscle Tonus / Q000502:physiology*; D019095:Point-of-Care Systems; D012026:Reflex, Stretch / Q000502:physiology*; D020521:Stroke / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*