Muscular rigidity is the passive movement of the limbs (as during a physical examination) that elicits ratchet-like-start-and movements through the range of motion of a joint (as of the elbow) and that occurs especially in individuals affected with Parkinson’s disease. The third major sign is rigidity (sometimes called “cogwheel rigidity”), peculiar to Parkinson’s disease. When a limb is bent, it seems to catch at regular points throughout its range of motion, much as second-hand jerks from interval to interval instead of smoothly traversing the face of a clock.
Symptoms of cogwheel rigidity
Rigidity refers to a type of hypertonia that involves increased resistance to movement. However, unlike other types of hypertonia, rigidity is not direction velocity-dependent. This means that there is the same amount of resistance regardless of whether a person bends or extends the affected limb and that the speed of motion does not affect muscle tone.
In people, with cogwheel rigidity, the limbs move with small jerky, or ratchet-like, movements. Alongside difficulty moving, stiffness from any type of rigidity may also cause pain and discomfort.
People with Parkinson’s disease have less dopamine, a type of neurotransmitter (a chemical in the brain). When there is less dopamine, the cells in the basal ganglia can’t connect or communicate as well. This means they can’t keep your emotions as smooth as they would otherwise be, which causes rigidity and other body movement issues common to Parkinson’s disease, like tremors.
Cogwheel causes include:
- Multiple system atrophy
- Progressive supranuclear palsy
- Corticobasal degenration
These conditions have similar symptoms but different causes. However, cogwheel rigidity is most common in Parkinson’s disease.
Other Parkinson’s symptoms
A person with Parkinson’s disease may also experience symptoms other than rigidity.
Other physical symptoms include:
- Balance problems
- Loss of sense of smell
- Swallowing difficulties
- Dry skin
- Problems with urinating
You can also treat cogwheel rigidity by treating the underlying condition. The most common and effective treatment for Parkinson’s disease is levodopa (I.dopa). It can help all symptoms, not just cogwheel rigidity. It’s often combined with carbidopa, which helps lessen side effects. Dopamine agonists and MAO-B inhibitors are other medications that treat Parkinson’s medicine. If no other medication has worked, some people with advanced Parkinson’s disease are candidates for deep brain stimulation. In this procedure, electrodes are positioned in the basal ganglia, where they send small electrical signals into the brain.