What is the Difference Between Spasticity and Rigidity

The main difference between spasticity and rigidity is that spasticity often affects antagonistic muscle groups, whereas rigidity occurs in both flexors and extensor muscles. Furthermore, spasticity occurs due to damage to the cortico-reticulospinal or pyramidal tracts, while rigidity occurs due to the dysfunction of extrapyramidal tracts and lesions in the spinal cord and mesencephalon. 

Spasticity and rigidity are two different types of hypertonia which arise in separate anatomical pathways. Spasticity is characterized by a sudden increase in muscle tone, occurring at a threshold velocity, angle, or amplitude, while rigidity is characterized by a high muscle tone that remains throughout the range of movement of the joint.  

Key Areas Covered 

1. What is Spasticity
     – Definition, Occurrence, Features
2. What is Rigidity
     – Definition, Occurrence, Features
3. What are the Similarities Between Spasticity and Rigidity
     – Outline of Common Features
4. What is the Difference Between Spasticity and Rigidity
     – Comparison of Key Differences

Key Terms 

Chronic Upper Motor Neuron Lesion, Hypertonia, Parkinson’s disease, Rigidity, Spasticity

What is Spasticity 

Spasticity is a type of hypertonia that causes continuous contraction, tightness, and stiffness in muscles. Generally, it occurs due to the lesions of pyramidal tracts, including corticoreticulospinal pathway. Moreover, the main characteristic feature of spasticity is tonic spasm, which interferes with the normal movement, speech, and gait. Further, it is unidirectional; hence, spasticity arises in the movement in a particular direction. Additionally, it is velocity-dependent and often occurs in fast movements.

Figure 1: Spasticity in Hand

Furthermore, some other causes of spasticity are the progressive degeneration of nerve fibers and myelin, multiple sclerosis, acquired brain trauma, stroke, and cerebral palsy. Also, like opening a pocket knife, the initial movement requires more tone in spasticity. Therefore, it is also known as “Clasp knife spasticity”. 

What is Rigidity 

Rigidity is another type of hypertonia. Generally, it occurs due to the extrapyramidal lesions as in Parkinson’s disease. Besides, its characteristic features are the stiffness, inflexibility, and the inability to bend, twist or stretch. Above all, muscle tension and rigor are the main features of rigidity. Furthermore, the rigidity is bi-directional. Therefore, it can cause stiffness in movements in all directions. Moreover, it does not depend on velocity. Therefore, rigidity can occur during slow movements as well.

Figure 2: Rigidity

Moreover, the other causes of rigidity include Wilson’s disease, multiple system atrophy, DMD (Dystonia musculorum deformans), MNS (Neuroleptic-malignant syndrome), Catatonia, CJD (Creutzfeldt-Jakob disease), etc. The two main types of rigidity are the “Cogwheel rigidity” and “Lead pipe rigidity”. The “Cogwheel rigidity” results in an intermittent increase in muscle tone. It also occurs due to the coexistence of basal ganglia diseases and tremor diseases. “Lead pipe rigidity” results in the uniform increase in tone. However, it occurs due to neuroleptic malignant syndrome and stiff man syndrome. 

Similarities Between Spasticity and Rigidity 

• Spasticity and rigidity are two states of hypertonia characterized by the high muscle tone. 
• They arise in distinct anatomical pathways. 
• Moreover, they lead to increased resistance to the passive movement of a joint. 
• Both are useful in neurological examinations.  

Difference Between Spasticity and Rigidity 

Definition 

Spasticity refers to a condition, which leads to an abnormal increase in muscle tone, interfering with movement and speech, while rigidity refers to a condition of muscles characterized by the inability to relax normally. Thus, this is the main difference between spasticity and rigidity.

Occurrence 

While spasticity often affects antagonistic muscle groups, rigidity occurs in both flexors and extensor muscles. 

Cause

Moreover, another important difference between spasticity and rigidity is their cause. Spasticity is a symptom of chronic upper motor neuron lesion, while rigidity is a symptom of Parkinson’s disease. 

Characterization 

Spasticity is characterized by a sudden increase in muscle tone, occurring at a threshold velocity, angle, or amplitude, while rigidity is characterized by a high muscle tone, remains throughout the range of movement of the joint.  

Amplitude and Velocity Dependency 

Another difference between spasticity and rigidity is that spasticity depends on both amplitude and velocity, while rigidity does not depend on both amplitude and velocity. 

Type of Resistance 

Furthermore, spasticity produces more resistance in one direction than the other direction, while rigidity produces the same resistance in all directions. 

Types 

The “Clasp knife spasticity” is the spasticity with more tone in the initial part of the movement, while the two types of rigidity are the “Cogwheel rigidity and “Lead pipe rigidity”. 

Treatment 

 Concerning their method of treatment, spasticity can be treated with the intrathecal pump, while rigidity can be treated by warm compression. 

Conclusion 

Spasticity is a condition of hypertonia, producing high muscle tone at a threshold of amplitude and velocity. Generally, it occurs in pyramidal tract lesions. It is also called the “Clasp knife spasticity” as the initial part of the movement requires more tone. On the other hand, rigidity is another type of hypertonia which produces high muscle tone independently from amplitude and velocity. However, it occurs due to the extrapyramidal tract lesions. Moreover, the two subtypes of rigidity are “Cogwheel rigidity” and “Lead pipe rigidity”. Therefore, the main difference between spasticity and rigidity is their occurrence and features.  

References:

1. Fearon, Conor, et al. “How Do I Examine Rigidity and Spasticity?” Movement Disorders Clinical Practice, vol. 2, no. 2, 2015, pp. 204–204., doi:10.1002/mdc3.12147.

Image Courtesy:

1. “Spastic hand 1” By Genusfotografen (genusfotografen.se) & Wikimedia Sverige (wikimedia.se) (CC BY-SA 4.0) via Commons Wikimedia   
2. “Image from page 123 of “Practical diagnosis: the use of symptoms in the diagnosis of disease” (1899)” By Internet Archive Book Images via Flickr