Hypertonia is a term sometimes used synonymously with
muscle spindles, and decreased synaptic inhibition.[2] These consequences result in abnormally increased muscle tone of symptomatic muscles.[3] 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 or physical therapy.[4]
Presentation
Symptoms associated with central nervous systems disorders are classified into positive and negative categories. Positive symptoms include those that increase muscle activity through hyper-excitability of the stretch reflex (i.e., rigidity and spasticity) where negative symptoms include those of insufficient muscle activity (i.e. weakness) and reduced motor function.[5] Often the two classifications are thought to be separate entities of a disorder; however, some authors propose that they may be closely related.[6]
Pathophysiology
Characteristic features, analogy, and pathophysiology of common types of hypertonia. GTO – Golgi Tendon Organ
muscle spasms, stiffening or straightening out of muscles, shock-like contractions of all or part of a group of muscles, and abnormal muscle tone. It is seen in disorders such as cerebral palsy, stroke, and spinal cord injury. Rigidity is a severe state of hypertonia where muscle resistance occurs throughout the entire range of motion of the affected joint independent of velocity. It is frequently associated with lesions of the basal ganglia. Individuals with rigidity present with stiffness, decreased range of motion and loss of motor control. Rigidity is a nonselective increase in the tone of agonist and antagonist without velocity dependence, and the increased tone remains uniform throughout the range of movement. On the contrary, spasticity is a velocity-dependent increase in tone resulting from the hyper excitability of stretch reflexes.[7] It primarily involves the antigravity muscles – flexors of the upper limb and extensors of the lower limb. During the passive stretch, a brief “free interval” is appreciated in spasticity but not in rigidity because the resting muscle is electromyographically silent in spasticity. In contrast, in rigidity, the resting muscle shows firing.[8]Dystonic hypertonia refers to muscle resistance to passive stretching (in which a therapist gently stretches the inactive contracted muscle to a comfortable length at very low speeds of movement) and a tendency of a limb to return to a fixed involuntary (and sometimes abnormal) posture following movement.[citation needed
]
Management
Therapeutic interventions are best individualized to particular patients.[citation needed] Basic principles of treatment for hypertonia are to avoid noxious stimuli and provide frequent range of motion exercise.[citation needed]
Physical interventions
PNF stretching has been used in many clinical settings to effectively reduce muscle spasticity.[10]
^Hall, C; Light, K (1990). "Heavy restrictive exercise effect on reciprocal movement coordination of closed-head injured subjects with spasticity". Neurology Report. 14: 19.
