9th Sept 2009.
The neglected pain of Parkinson’s
Nowadays, the manifestations of Parkinson’s are known to be “two sides of the same brain” – they consist of both motor and non-motor symptoms. Parkinson’s is no longer known as only a movement disorder. Parkinson’s specialists have shifted their focus of attention to the commonly occurring non-motor symptoms such as constipation, depression and anxiety, which can even precede the motor symptoms of Parkinson’s by a few years. Towards the later stage of Parkinson’s, the non-motor symptoms can even be more disabling than the motor symptoms.
In the context of Parkinson’s, when one previously mentioned about pain, it usually referred to the emotional pain or mental agony due to the relentless progression of physical disability. However, the concept of pain in Parkinson’s has changed over the recent years due to the increasing recognition of a physical kind of pain, which is another example of the non-motor symptoms of Parkinson’s. Throughout this article, the term “pain” refers to the physical pain.
What are the causes of pain in Parkinson’s?
a) Non-Parkinson’s disorders
Just as any other non-Parkinson’s patients, Parkinson’s patients (especially the older patients), have many coexisting medical disorders which result in pain, e.g. “bony spurs” at the neck which compress the nerves (leading to shoulder or arm pain) and diabetes (which often causes painful nerve disorders, especially at the hands and feet). Some Parkinson’s patients, especially at the advanced stage of illness, develop tendency to fall (loss of balance) which leads to fracture of hip and spine. Knee joint disorder (osteoarthritis) is another common cause of pain.
b) Parkinson’s-related disorders
However, in addition to pain caused by the non-Parkinson’s medical conditions mentioned above, many people are not aware that 39.3% of Parkinson’s patients have chronic pain which is directly related to Parkinson’s itself (Negre-Pages L et al, 2008). These researchers discovered that pain was twice more frequent in Parkinson’s patients than in patients without Parkinson’s. This study concluded that chronic pain is frequent but underreported in Parkinson’s. It was recommended that doctors should be more aware of this problem and improve the pain-killer strategies.
How do we know that the pain is related to Parkinson’s?
There are several useful pointers (Quinn NP, 1998).
What are the Parkinson’s-related disorders which give rise to pain?
i) Muscle contraction (rigidity)
Muscle contraction is the most common cause of Parkinson’s-related pain. The pain is caused by persistent muscle contraction, and commonly felt at one side of the body such as the shoulder, arm and leg. Sometimes, the pain may be felt at the neck. It is usually described as constant, aching pain which affects the whole part of the limb. This pain affects the side of the body where the motor symptoms are more severe or have originated from (as illustrated by Patient 1). The pain is worse during the “wearing off” periods, as the muscle spasm or contraction is intensified at this stage.
The pain has a tendency to precede the onset of motor symptoms by 1-2 years. Shoulder pain and frozen shoulder are known to be the early symptoms of Parkinson’s (Cleeves L, 1989; Riley D et al, 1989). As such, some Parkinson’s patients who initially experienced shoulder pain (as illustrated by Patient 2) or frozen shoulder are referred to the orthopedic (bone) specialist before they are subsequently discovered to have Parkinson’s.
Treatment: Parkinson’s medications usually help in relieving the pain. Physiotherapy can also be beneficial.
Case illustrations (true stories)
A 62 year-old man has been diagnosed to have Parkinson’s for two years. His initial complaints were stiffness, tremor and difficulty in movement on the left side of his body. He responded well to Ropinirole 2 mg three times a day.
Recently, he started to have mild and constant aching pain on the left upper and lower limbs, which was present the moment he woke up in the morning. The aching pain was felt all over the left upper and lower limbs, and affected his concentration while doing his work. He did not feel any tingling sensation or numbness. Being a right-handed person, his hand function was relatively preserved.
Physical examination revealed mask-like facial expression and moderately severe stiffness of the left upper and lower limbs. He also had rest tremor on the left side. The movement of the left upper limbs was quite slow. The right limbs were fairly normal. No dystonia or dyskinesia was noted. When he walked, the left arm did not swing.
The muscle stiffness and tremor did not give him much trouble as he could even travel overseas regularly to carry out his work. His physical mobility was not affected. Obviously, the left-sided pain was more disabling than his motor symptoms.
A golden rule in the management of Parkinson’s is that one should not attribute every single new symptom to Parkinson’s – there could be other possibility such as nerve disorder. An important consideration was compression of the nerve in the neck due to bony spurs. An MRI scan of his neck spine did not show any evidence of nerve compression. Computerized nerve study also did not show any evidence of nerve disorder which could account for the aching sensation of the left-sided limbs.
Following the increase in the dose of Ropinirole to 4 mg three times a day, his pain was relieved. He also reported that the standard painkillers helped to reduce the pain, to a certain extent.
However, he had another problem that had worsened his left-sided pain. He had been a socially active businessman who traveled overseas regularly. The very diagnosis of Parkinson’s and also the difficulty in going to airport had made him quite depressed. I believe that his underlying depression has contributed to his left-sided pain.
I explained to him that he had underlying depression and could benefit from antidepressant medications. However, he was not keen to take antidepressant because he thought he could cope with his emotional disorder. True enough, he eventually managed to live with his pain and continued his daily work, till today.
This gentleman was quite disabled by the aching pain of the left upper and lower limbs which was caused by the muscle stiffness of Parkinson’s. Treatment with Parkinson’s medications often relieves the pain. In any Parkinson’s patient with pain, any underlying depression should be considered. Treatment with antidepressant can also improve the pain. The relationship between pain and depression in Parkinson’s is further discussed below.
Mr. Quah (not the real name), a 56 year-old Chinese man, worked as an acupuncturist at a traditional Chinese medical clinic in Kuala Lumpur.
In October 2004, he had a new problem. He had left shoulder and arm pain which he described as constant aching pain. His left shoulder also became stiff.
He consulted a general practitioner, who said, “What you are experiencing is due to some “bony spurs in your neck” which are compressing your nerves, causing the left arm pain.” Mr. Quah was given some painkillers and nerve medications, which did not relieve the aching left arm and stiff neck.
Subsequently, he was referred to the orthopedic (bone) surgeon who also told him that he had “bony spurs in the neck”. He was recommended to undergo physiotherapy at a local teaching hospital, where he underwent regular neck traction (for the bony spurs in his neck). Again, his symptoms did not improve.
By April 2005, he noticed that his left hand had started trembling. The tremor was worse when he was anxious or doing his acupuncture work. Being a left-handed person, Mr. Quah had difficulty inserting the acupuncture needles, to the extent that his clients had complained that it felt more painful than before. His body movement became slow. It was only at this juncture that the neurologist diagnosed him to have Parkinson’s.
Today, he is on Pramipexole 0.5 mg tds, Amantadine 100 mg tds and Benzhexol 2 mg tds. The shoulder pain has almost completely disappeared. His clients do not complain anymore that his acupuncture treatment is painful.
This gentleman had early manifestations of Parkinson’s such as left shoulder and arm pain that was initially and wrongly attributed to “bony spurs in the neck”. As many doctors and Parkinson’s patients are not aware of the non-motor symptoms of Parkinson’s, the one-sided pain in Parkinson’s is commonly attributed to disorders of neck bone (cervical disc prolapse). Obviously, this patient had walked into the “wrong clinic”.
Dyskinesia is uncontrollable, jerky and irregular body movement that occurs partly as a side effect of levodopa. When severe, dyskinesia results in prolonged episodes of muscular contraction which have the same effect of “running non-stop for a few kilometers”. Many patients feel exhausted after an episode of dyskinesia, which follows each dose of levodopa. Thus, pain due to dyskinesia occurs as part of the “on” periods. Dyskinetic pain is often described as aching pain. As dyskinesia is a common complication of levodopa treatment, and almost all Parkinson’s patients eventually need levodopa, dyskinesia is an important cause of pain in Parkinson’s.
Furthermore, the twisting movement of dyskinesia may aggravate the non-Parkinson’s causes of pain such as neck bone disorder (cervical disc prolapse).
Treatment: measures to reduce dyskinesia helps in relieving of dyskinetic pain. These include reducing the individual doses of levodopa, adding dopamine agonists and / or amantadine, and the use of Apomorphine skin injection.
Dystonia refers to sustained, forceful and twisting body moments that lead to abnormal body position or deformities. Dystonia can affect almost every part of the body, particularly the neck and foot. Commonly, dystonia results in painful muscle cramps affecting the calf muscles, which is associated with upgoing toes. Dystonic pain is most commonly felt upon awakening in the morning, when the effect of the previous evening dose of Parkinson’s medications has worn off. In other words, pain due to dystonia occurs as part of the “off” periods.
Treatment: Dystonia does not always result in significant pain. In these cases, it is not necessary to start any specific treatment. In fact, many patients learn to get use to the dystonia. However, when the dystonic pain is unbearable or disabling, measures which relieve the early morning dystonia can reduce the dystonic pain, such as evening dose of long-acting levodopa (Madopar HBS or Sinemet CR) and dopamine agonist. In severe cases, injection of Botox (a medication which reduces muscle contraction) is needed.
iv) Restless leg syndrome (RLS)
RLS is a neurological disorder which is associated with Parkinson’s. RLS is characterized by unpleasant sensations in the legs which are typically present when the legs are at rest, e.g. sitting or lying on bed. The unpleasant sensations lead to an uncontrollable urge to move the legs (e.g. walking about the room) which relieves these unpleasant feelings. RLS sensations are often described as burning, creeping, tugging, or like insects crawling inside the legs. Sometimes, the unpleasant abnormal sensations can be irritating or even painful.
Treatment: as RLS is also related to abnormal dopamine activity in the brain, dopamine agonists are helpful in relieving the symptoms of RLS.
v) Central pain
This is a rare pain disorder in Parkinson’s. It is thought to be a direct consequence of Parkinson’s itself (i.e. the changes in the brain of Parkinson’s patients), and not due to the disorders mentioned from i) to iv) above. The basal ganglia (the part of the brain which is principally affected in Parkinson’s) may have a role in modifying sensory information in the body (Chudler EH, 1995). Thus, a disturbance in the function of basal ganglia in Parkinson’s may result in a lower pain threshold in Parkinson’s patients compared with healthy people (Djaldetti R et al, 2004). In addition, dopamine has been known to play a role in the regulation of pain in the brain.
Manifestations of central pain include painful, burning, stabbing, aching, itching, or tingling sensations, which may even precede the motor symptoms of Parkinson’s. Central pain can affect any part of the body.
It has to be emphasized other medical disorders which commonly cause such pain symptoms (e.g. diabetes, vitamin B deficiency) be excluded before one makes a diagnosis of central pain. A computerized nerve conduction study should also be considered to exclude nerve disorders of the limbs.
Treatment: it is difficult to treat the central pain in Parkinson’s. Currently, there is no known effective and specific treatment for this disorder. Unfortunately, central pain responds poorly to Parkinson’s medications.
Some people have suggested using gabapentin (Neurontin), but this has not been unequivocally confirmed to be effective. Consulting a pain specialist may help.
The rarer types of pain in Parkinson’s
Some Parkinson’s patients complain of oral and genital pain which tends to fluctuate in severity with the motor symptoms of Parkinson’s, and responds to Parkinson’s medications (Ford B et al, 1996). Burning mouth is another complaint among Parkinson’s patients which is poorly understood (Clifford TJ et al, 1998).
The relationship between pain and depression in Parkinson’s
Depression and pain are common in Parkinson’s. A significant relationship between pain and depression was found among Parkinson’s patients (Ehrt U, 2009). Depression seems to increase the severity of pain in Parkinson’s patients (depressed Parkinson’s patients seem to be more sensitive to pain). On the other hand, the presence of pain may lead to depression. Thus, there seems to be a “chicken-and-egg” relationship between pain and depression in Parkinson’s.
Treatment: any coexisting depression should be considered in any Parkinson’s patient with pain, and vice versa, as illustrated in the following story:
Case illustration (true story)
A 67-year-old lady was recently diagnosed to have very mild Parkinson’s. She also complained of bilateral feet pain which is described as aching, and triggered by prolonged standing or walking. This aching pain has troubled her to the extent that she can’t stand for longer than 20 minutes, and unable to carry out her daily activities such as cooking and cleaning up the home. Almost everyday, she asked her children to bring her to the doctor’s clinic to treat her feet pain.
When I examined her, all I could notice was flat feet (the loss of the normal curvature of the base of the foot). There was hardly any physical evidence of Parkinson’s. She was referred to the orthopedic (bone) surgeon who agreed that she had flat feet, which caused her feet pain. However, the surgeon did not advise her to undergo feet surgery as he thought her feet problem was not severe.
Despite the reassurance of the surgeon, she was still so preoccupied with the feet pain. Each time she came back to my clinic, her complaint was always the same – “I can’t walk around at home or cook because my feet are hurting me”.
Having noticed that she also had a few symptoms of depression such as insomnia, lethargy and loss of appetite, I asked her whether there was any personal problem which was bothering her. She said, “No. There is nothing which is making me upset except my feet pain.”
After asking her the same question several times over a few months period, finally she managed too open up to me. “I feel sad because of my son. He can’t get along with all my other children.”
Further questioning revealed that she had family problem which had made her depressed. She had a rebellious son who refused to speak to each of his siblings.
I told her that 80% of her disability was caused by depression, while her flat feet and Parkinson’s merely contributed to 10% each to her disability. Her “painful feet” was merely a way for her to distract herself from her son’s rebellious behaviour, and thus relieving her mental stress.
So, instead of focusing on her feet pain, I suggested to her that we should focus on her main problem, which was depression. I started her on antidepressant. A few weeks later, when I saw her again, she did not complain about the feet pain anymore.
Why is pain under-recognized in Parkinson’s?
Just as the non-motor symptoms, the pain in Parkinson’s is obviously under-recognized and under-treated. Many doctors and patients are still preoccupied with the movement disorder in Parkinson’s, and thus not paying enough attention to the pain in Parkinson’s.
The non-specific nature of pain in Parkinson’s also makes it difficult to be recognized. For example, symptoms such as burning sensation, numbness and tingling are also found in other nerve disorders, especially diabetes.
The DBS surgery and pain
Since the DBS surgery results in improvement of body stiffness, dyskinesia and dystonia, it is not surprising that a study has reported that DBS surgery improved pain in Parkinson’s patients (Kim HJ et al, 2008). Interestingly, the DBS surgery has been reported to be beneficial in the management of chronic pain due to nerve disorders in non-Parkinson’s patients.
Parkinson’s is a physically painful brain disorder. The pain in Parkinson’s is under-recognized and under-treated. Various treatment options for pain are available such as Parkinson’s medications and DBS surgery, which can potentially improve the quality of life. The relationship between pain and depression in Parkinson’s should be recognized. The optimal treatment of Parkinson’s includes the relief of both motor and non-motor symptoms.
In other words, Parkinson’s does not have to be that painful.
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