Is Spasticity a Syndrome? A Historical Perspective on Spasticity Definitions and Descriptions

"Spasticity" has long been used as a generalized term for a constellation of distinct positive motor signs arising from a central nervous system lesion, creating ambiguity in identifying individual impairments. These include spasticity sensu stricto-the velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex, as defined by Lance in 1980-as well as spastic dystonia, spastic co-contraction, and spasms. Drawing on our clinical experience and collaborative work within the Toxnet group (www.toxnet.net), we believe that using spasticity as a broad diagnostic label creates ambiguity and may obscure the specific impairments contributing to the clinical presentation. Such generalization may compromise treatment decisions and outcomes and is compounded by using manual tools like the Tardieu and modified Tardieu Scales, which lack evidence of validity and reliability, and the Ashworth and modified Ashworth Scales, which do not measure the velocity-dependent nature of spasticity or provide dependable insights into the mechanisms driving the torque changes. To optimize clinical assessment precision and treatment outcomes, we propose "spasticity syndrome" as a new umbrella term encompassing the spectrum of clinical manifestations and underlying pathologies associated with upper motor neuron injury, alongside non-neural peripheral changes and patient-reported symptoms.