From the Guidelines
Spasticity and tonicity are distinct concepts in neuromuscular function, with spasticity being a pathological increase in muscle tone and tonicity referring to the normal background tension present in muscles at rest. Tonicity is essential for maintaining posture and preparing muscles for movement, regulated by the balance between excitatory and inhibitory signals from the central nervous system 1. Spasticity, on the other hand, is characterized by velocity-dependent resistance to passive stretching and exaggerated deep tendon reflexes, occurring due to damage to upper motor neurons in the brain or spinal cord, disrupting the normal inhibitory pathways 1.
Key Differences
- Spasticity is a pathological condition, while tonicity is a normal physiological state
- Spasticity causes stiffness, involuntary muscle contractions, and can lead to pain, functional limitations, and eventually contractures if untreated, whereas normal tonicity allows for smooth, coordinated movements
- Treatment options for spasticity include physical therapy, oral medications like baclofen or tizanidine, botulinum toxin injections, and in severe cases, surgical interventions, while normal tonicity requires no intervention 1
Treatment Options
- Physical therapy, such as positioning, passive stretching, and range of motion exercise, can provide relief from spasticity 1
- Oral medications like baclofen or tizanidine can be useful for generalized spastic dystonia, but may result in dose-limiting sedation or other side effects 1
- Targeted injection of botulinum toxin into localized upper or lower limb muscles can reduce spasticity and improve range of motion or gait function 1
- Intrathecal baclofen therapy may be useful for severe spastic hypertonia that does not respond to other interventions 1
From the Research
Definition and Characteristics
- Spasticity is a velocity-dependent increase in muscle tone and uncontrolled, repetitive, involuntary contractions of skeletal muscles 2.
- It is part of the upper motor neurone syndrome manifesting as increased tone, clonus, spasms, spastic dystonia and co-contractions 3.
- Spasticity can be described by a documentation system grouped along clinical picture, aetiology, localisation, and additional central nervous system deficits 4.
Comparison with Tonicity
- Tonicity refers to the normal muscle tone that is present in muscles at rest.
- Spasticity is different from tonicity in that it is a pathological increase in muscle tone that is velocity-dependent and can cause significant pain and limited mobility 2.
- Rigidity, another type of hypertonia, is also distinct from spasticity and tonicity, and is caused by dysfunction of extrapyramidal pathways, most commonly the basal ganglia 5.
Key Differences
- Spasticity is characterized by abnormally high muscle tone that is amplitude and velocity dependent, whereas rigidity is independent of velocity and remains constant throughout the range of movement of the joint 5.
- Spasticity often asymmetrically affects antagonistic muscle groups, whereas rigidity is present in flexors and extensor muscle groups equally 5.
- The management of spasticity involves identification and elimination of triggers, neurophysiotherapy, oral medications, focal injection of botulinum toxin, and surgical resection of selected dorsal roots of the spinal cord 3.