Hypertonia is a term sometimes used synonymously with
spasticity in the literature surrounding damage to the
central nervous system, namely upper motor brain lesions. Impaired ability of damaged
motor neurons to regulate descending pathways gives rise to disordered
spinal reflexes, increased excitability of
muscle spindles, and decreased
synaptic inhibition. These consequences result in abnormally increased
muscle tone of symptomatic muscles. Some authors suggest that the current definition for spasticity, the velocity-dependent over-activity of the
stretch reflex, is not sufficient as it fails to take into account patients exhibiting increased muscle tone in the absence of stretch reflex over-activity. They instead suggest that “
reversible hypertonia” is more appropriate and represents a treatable condition that is responsive to various therapy modalities like drug and/or physical therapy.