Rigidity
Clinic
- Rigidity is an increase in muscle tone leading to a resistance to passive movement throughout the range of motion
- Its quality is exactly opposite to Spasticity
- Opposite to Spasticity, it does not depend on the speed and range of movement and is always present even in slow and very slow movements
- Opposite to Spasticity, it is present in both extensor and flexor muscle groups and creates a uniform and homogeneous quality. (lead pipe) [1]
- It comes from extrapyramidal tracts esp BG, mesencephalon and spinal cord. Spasticity is related to Pyramidal tract
- Since it is often caused by BG diseases, tremors also accompany it and this causes cogwheeling.
Pathophysiology of Rigidity in PD
PD rigidity is characterized by increased muscle tone to palpation at rest, reduced distension to passive movement, increased resistance to stretching, and facilitation of the shortening reaction [82]. Rigidity is more marked in flexor than extensor muscles, may be enhanced by voluntary movement of other body parts, and is more remarkable during slow than fast stretching, and these features help differentiating PD rigidity from spasticity, which is worse during fast displacement [82, 83]. Cogwheel phenomenon is the result of coexisting rigidity and tremor [82].
The pathogenesis of PD rigidity has been hypothesized to include changes in the passive mechanical properties of joints, tendons, and muscles, the enhancement of stretch-evoked reflexes from segmental spinal or supraspinal activity, and abnormalities in peripheral sensory inputs that may influence the response to muscle stretch [83–86]. Studies on spinal reflexes indicate a shift of spinal cord motoneurons towards increased activity in response to peripheral stimulation [84, 85] and increased response to muscle stretch [83], with a possible contribution of transcortical long-latency stretch reflex [86]. How these changes are associated with dopamine deficiency and BG output abnormalities, which are stipulated by the classical BG pathophysiological model, is still unclear [82].
Analogues
Rigidity has three analogues
Miasms
- ↑ Published online 2015 Mar 28. doi: 10.1002/mdc3.12147 PMCID: PMC6183506 PMID: 30363919 How Do I Examine Rigidity and Spasticity? Conor Fearon, MB MRCPI, 1 Laura Doherty, MB, 1 and Tim Lynch, MB FRCPI 1 Mov Disord Clin Pract. 2015 Jun; 2(2): 204.