Introduction
Parkinson’s disease (PD) is a multisystem condition of unclear aetiology that affects 1%–3% of the population aged >65 years.1 It presents with motor, neurological, psychiatric, and gastrointestinal manifestations that typically progress slowly over the course of a decade or more.1 Forty per cent to 80% of individuals with PD experience significant levels of pain and it is an often unrecognised and under-treated non-motor symptom of the disease.2 Its prevalence in PD is greater than age-matched controls with other chronic diseases. With an aim to increase awareness of this symptom in general practice, this article presents an overview of the different pain syndromes associated with PD and their management.
Pain in PD can either be unrelated, such as osteoarthritis, or related pain that can be defined as pain that starts after PD diagnosis, responds to PD treatment, is maximal on the more affected side, and has no clear alternative cause.3 The main types of pain syndromes encountered in PD are central pain, peripheral pain, musculoskeletal pain, and pain due to dystonia and akathisia.2,4
Central pain syndrome
Central pain syndrome is attributed to defective pain processing and depletion of dopamine in the brain. Its clinical presentation is heterogeneous and vague.5 Central pain can present as bizarre visceral sensations with elements of dysautonomia such as abdominal cramps or hot flushes, as formication (a sense of insects crawling over the skin), or as increased responsiveness to mild or non-painful stimuli. Because of symptom vagueness and overlap with other types of pain, patients often find it difficult to volunteer symptom information. However, as treatment modalities are different for central pain syndrome, it is important for clinicians to elicit this information.4
Peripheral neuropathic pain
This pain has a reported prevalence of 35.5% to 55.0% in PD, and the prevalence of large-fibre neuropathy in idiopathic PD is estimated at 16.3%.6 The main symptoms described include burning, pins and needles, tingling, and spontaneous pain. Some patients complain of oral or genital pain. Radiculopathy has high incidence in PD and is caused by abnormal posture resulting in nerve root compression or dorsal root ganglion impingement.4 This pain is often confined to the distribution of a nerve root as seen in usual types of radiculopathies. Clinicians should also consider other common causes of neuropathy in patients with PD presenting with peripheral pain.
Musculoskeletal pain
Pain arising from joints, muscles, and the axial skeleton is the most common PD pain symptom and can present as a prodromal symptom. The disease process causes camptocormia (abnormal forward trunk flexion) and Pisa syndrome (abnormal lateral trunk flexion) accompanied by muscular rigidity that leads to abnormal posture and stress on ligaments, facet joints, and soft tissue resulting in pain. Increased prevalence of osteoporosis and defective pain modulation pathways further complicate this picture. The musculoskeletal pain presentation is similar to patients without PD; however, subtle postural abnormalities need to be explored clinically as this pain is not amenable to traditional pain relief medication and needs physiotherapeutic interventions and rehabilitation. Low back pain, shoulder pain, arthralgias, and general muscle aches and cramps are the most frequent complaints. Prevalence of low back pain is 50% higher in PD than age-matched controls and is a frequent cause of GP visits.3,4 Furthermore, unilateral musculoskeletal pain, especially in shoulder arm distribution, is highly specific of PD and may predate rigidity and bradykinesia.
Pain due to akathisia and dystonia
This subtype shares common features and possibly pathogenic mechanism of the above three pain types. It is seen as an offshoot of the OFF phenomenon (phenomenon where there is re-emergence of PD symptoms when the plasma levodopa level decreases).4 Akathisia is another treatment-related phenomenon that is not painful but has highly displeasing sensations manifesting as subjective restlessness and an urge to move. Dystonic pain in PD is another pain experienced because of forceful contraction of a muscle group or body area. It is usually, but not always, seen in levodopa-treated patients, and in them its identification is important as it may respond to optimisation of conventional anti-Parkinsonian treatment.8
Management
Primary care physicians play a pivotal role in pain management as treatment options rely on accurately recognising the type of pain, which is often not easy to clinically differentiate. Assessing the severity of pain syndromes can also be clinically challenging.4 The, often ignored, essential first steps in managing pain are non-pharmacological. Advice on a balanced diet is important as this can address pains related to constipation, decreased bone density, and low mood. Food affects levodopa absorption resulting in steady state levels of dopamine, which may alleviate some symptoms. Early recognition and treatment of depression also helps in pain modulation. Exercise therapy, involving correct posture and muscle strengthening, improves musculoskeletal pain and quality of life. Acupuncture and alternative therapies such as mindfulness or meditation may be of value in motivated patients. A multidisciplinary approach to care involving specialist nurses, physiotherapy, occupational therapy, and social prescribing is highly recommended.
As there is limited good evidence and no consensus guidelines for pharmacological management of pain in PD, experts advocate using the modified World Health Organization pain management ladder as a graded pain management protocol. Non-steroidal anti-inflammatory drugs, tricyclic antidepressants (TCAs)/selective serotonin reuptake inhibitors, and opioid analgesics such as low-dose oxycodone should be introduced stepwise as the mainstay of treatment.9 Pregabalin can be used when the above options are ineffective.10
Pharmacological options for specific pain types
Pain due to motor fluctuations: may respond to conventional dopaminergic therapy and dose adjustments should be the first logical step.
Neuropathic pains: TCAs are recommended first line followed by addition of weak opioids. Anti-epileptics and local capsaicin patches can be used for localised neuropathic pain.
Central pain: although rotigotine patches are more effective than dopamine, there are no other effective treatment options available for this pain. Deep brain stimulation (DBS) can improve motor symptoms but not pain in PD.9 Ongoing clinical trials involve modalities such as N-methyl D-aspartate (NMDA) receptor modulators,11 8% capsaicin patches, and low-frequency DBS of substantia nigra.
Box 1 presents a summary of the pain syndromes and treatment options. It is important to note that, despite all the above measures, a considerable subset of patients will continue to experience pain. However, the improvement in quality of life in those responsive to treatment highlights the need to accurately recognise and treat pain in PD appropriately.
| Type of pain | Characteristic features | First-line treatment | Second-line treatment |
|---|
| Musculoskeletal pain | Aching or cramping
Arthralgia or joint tenderness
Myalgia | Non-steroidal anti inflammatory drugs (NSAIDs)
Physiotherapy
Occupational therapy | Low-dose opioids
Tricyclic antidepressants |
| Central neuropathic pain | Bizarre sensation
‘Inner’ sensation
Unexplained sensations
Autonomic symptoms | Tricyclic antidepressants
Weak opioids | Strong opioids
Anticonvulsants
New therapies |
| Peripheral neuropathic pain | Pain in nerve or nerve root distribution
Burning sensation
Pins and needles
Sharp pain | Local capsaicin
Tricyclic antidepressants | Gabapentin
Anticonvulsants
Opioids |
| Pain due to akathisia | Restlessness
Urge to move | Dopamine agonists | Intestinal levodopa gel |
Box 1. Summary of pain syndromes and treatment options
As a pragmatic approach to the management of PD-related pain, this article proposed a series of steps (Figure 1).
Figure 1. Steps in the management of Parkinson’s disease-related pain in primary care.
Notes
Provenance
Freely submitted; externally peer reviewed.
Competing interests
The authors have declared no competing interests.
- © British Journal of General Practice 2024
