‘Causal relation between spasticity, strength, gross motor function, and functional outcome in children with cerebral palsy: a path analysis’

Abstract

SIR–In their recent article 1 Kim and Park fail to deal with the entirety of Dr Lance’s classical definition of spasticity. 2 His carefully drafted statement documented the consensus of the 1979 symposium of 44 actively engaged neurological investigators (including me): ‘Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (‘muscle tone’) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex, as one component of the upper motor neuron syndrome. This did not preclude discussion of other features of the upper motor neuron syndrome resulting from release of flexor reflexes, such as flexor spasms, or the negative symptoms such as the pattern of weakness and loss of dexterity caused by withdrawal of the influence of descending motor pathways.’ 2 Thus spasticity is not a subjective symptom like headache or diplopia. It is rather an objective observation of the professional examination, like a cardiac murmur or a dilated pupil. There is abundant evidence that the truly disabling negative symptoms, often more impaired dexterity than strength, are directly correlated with the degree of disconnection of the target motor neuron population from the complexly integrated control of forebrain and hindbrain nerve structures. This loss of fine control and force is neither augmented by antagonist muscle stretch reflexes 3 or improved by systemic medication, fusimotor blockade, 4 or dorsal rhizotomy. 5 Nor is the degree of clumsiness directly correlated with the prevalence of spasticity. 6 The Ashworth Scale has never been more than an amateur parascientific game, with personal impressions of stiffness and absent replicable physical parameters. Recently, Fleuren et al. 7 have gone to the trouble of proving that the Ashworth Scale is worthless. Occam’s razor requires cessation of the senseless and useless demonization of the spasticity epiphenomenon. Absent evidence-based potions, patients should be assisted to practice toward maximal autonomous function.