Rigidity, or the stiffness and inflexibility of the limbs, neck or trunk, is one of the primary motor symptoms of Parkinson’s disease (PD), although not all patients with PD experience rigidity. This rigidity can be uncomfortable or painful and may contribute to a reduced range of motion. Muscles usually stretch when they move and relax when they are at rest, and rigidity causes the muscles to remain stiff and unable to rest. The other main primary motor symptoms are tremor (particularly a tremor when the limb is at rest), postural instability (impaired balance or difficulty standing or walking), and bradykinesia (gradual loss and slowing down of spontaneous movement).1
Along with bradykinesia, rigidity may cause a person with PD to not swing their arms when walking. It may also cause:
- Stiff, inflexible muscles
- Pain and muscle cramps
- A fixed facial expression, sometimes called a “mask”
- Difficulty turning over in bed
- Difficulty getting out of chairs
- Trouble writing or buttoning clothes2
Why does Parkinson’s disease cause rigidity?
The exact disease process that causes the rigidity seen in many patients with PD is not precisely understood, although it is believed that it is associated with the reduction in dopamine, a neurotransmitter (chemical messenger) that relays the message to particular areas of the brain to produce smooth, purposeful movement. These other parts of the brain are organized into a circuit called the basal ganglia. When PD damages large numbers of these dopamine-producing neurons, communication across neurons in this circuit is disrupted and the motor symptoms of PD appear, including rigidity. Research has found that when the motor symptoms of PD appear, 60-80% of the neurons that generate dopamine have been destroyed.1,3
Treating rigidity in Parkinson’s disease
While there is no known cure for PD at this time, and there are not currently any treatments to slow or stop the natural progression of the disease, there are a number of treatments that can manage symptoms like rigidity. Treatment is tailored to the individual patient and may include medications, surgery (deep brain stimulation), and complementary or alternative medicine.
Most patients with PD are started on medication to help manage their symptoms. Initial therapy is usually levodopa (administered with carbidopa), dopamine agonists, and/or monoamine oxidase-B (MAO-B) inhibitors. The combination of levodopa and carbidopa is the most effective treatment available for the management of motor symptoms of PD, including rigidity. However, it can cause a side effect known as dyskinesia, which are abnormal involuntary movements. Dopamine agonists are less effective on the motor symptoms of PD but have a lower rate of causing dyskinesia, although they have other side effects. MAO-B inhibitors are less effective than levodopa or dopamine agonists, however they have fewer side effects. Choice of therapy should be customized to the individual patient with an understanding of the risks and benefits of each class of medication.4
In addition to medication, physical therapy can help with muscle cramps, and regular exercise and stretching are beneficial to strengthen muscles and maintain flexibility. Trying to move throughout the day can reduce symptoms. Exercises such as yoga, tai chi, and weight lifting have also been shown to help. The more high intensity the exercise is, the more beneficial it is at alleviating symptoms. Assistive devices such as walkers or canes can also be helpful.
For some people with PD whose symptoms are not adequately controlled with medication and/or exercise, surgery to perform deep brain stimulation may be an option. As with medication and exercise, surgery does not cure or change the course of the disease progression, but it may help with the symptoms of PD.5