Pain in Dystonia and Parkinsons

Question 1

main clinical features of Dystonia and Parkinsons

Answer 1

Dystonia

Characterised by sustained muscle contractions, resulting in twisting, repetitive movements and abnormal postures. These movements are typically patterned and may be tremulous. The distribution of dystonia can be focal, segmental, multifocal, hemidystonia or generalised with different body parts affected:

• Cervical Dystonia: Involves the neck muscles, cuasing abnormal head postures and is the most common type of focal dystonia
• Writer’s Cramp: Affects the hand and arm during writing
• Meige Syndrome: A combination of blepharospasm (eyelid closure) and oromandibular dystonia (jaw and tongue movements)
• Truncal and Limb Dystonia: Can affect the trunk or limbs leading to challenges in gait and coordination

(Albanese et al., 2013)

Parkinson’s Disease

PD is a neurodegenerative disorder defined by four cardinal motor symtpoms:

• Bradykinesia: Slowness of movement and a reduction in spontaneous movement
• Rigidity: Stiffness in the limbs or trunk
• Resting Tremor: Involuntary, rhythmic muscle contraction affecting mostly the hands (Pill-rolling)
• Postural Instability: Impaired balance, which increases the risk of falls

(Jankovic, 2008)

Both Dystonia and PD symptoms are attributed to the abnormal firing in the basal ganglia circuit. In PD, there’s degeneration of dopaminergic neurons while in dystonia, the pathophysiology is more complex, often involving abnormalities in the same basal ganglia circuit from brain injury, stroke, drug exposure or idiopathic.

Question 2

key factors associated to development of Pain in Dystonia and Parkinsons

Answer 2

Pain in Dystonia

In dystonia, pain is often associated with sustained, involuntary muscle contractions that are characteristic of the disorder. For instance, cervical dystonia, which involves the muscle of the neck, can cause severe local pain as well as referred pain in areas such as the shoulder and back

• Muscle over use and strain: Continuous muscle contractions and abnormal postures lead to muscle fatigue, soreness and pain
• Nervous system dysfunction: An alteration in the way the CNS processes pain, potentially due to changes in neurotransmitter levels in the areas of the brain responsible for motor control and sensory processing (Prefrontal cortex, amygdala)

Pain in Parkinson’s Disease

• Musculoskeletal pain: Caused by rigidity and dystonia, leading to abnormal postures and overuse of certain muscle groups
• Neuropathic pain: due to neurodegeneration and possibly small fibre neuropathy which can manifest as burning, tingling or stabbing sensations
• Central Pain: Altered pain processing at the spinal or cerebral level, likely as result of the widespread effects of dopamine loss on the central nervous system

(Tinazzi et al., 2006) pain in PD

(Conte et al., 2013) pain in dystonia

Question 3

basic mechanisms of pain in Dystonia and Parkinsons

Answer 3

Dystonia

• Muscular Overactivity and Strain
• Altered nociception: higher density of deep pain receptors in the affected muscles especially in the neck muscles with cervical dystonia
• central sensitisation: Alterations in the cortical somatosensory system may lead to central sensitisation where the nervous system goes through a process that increases its responsiveness to stimuli

PD

• Nociceptive pain: Arising from musculoskeletal sources like rigidity and dystonia, which cause abnormal postures and overuse syndromes
• Neuropathic pain: Related to peripheral nerve damage, possibly due to the disease process itself affecting small nerve fibers
• Central Pain: Stemming from dysfunction in the central processing of pain, which might be related to the dopaminergic deficits that characterise PD

(Tinazzi et al., 2009) PD pain

Question 4

main treatments of pain in Dystonia and Parkinsons

Answer 4

Dystonia

• Botulinum Toxin Injections: Focal dystonia and can significantly reduce pain by causing temporary muscle paralysis thus alleviating abnormal postures and movements
• DBS: For refractory cases, especially in generalised or segmental dystonia, DBS of the globus pallidus interna can be effective in reducing symptoms, including pain
• Physiotherapy: May help alleviate pain by improving posture and reducing muscle tension

PD

• Optimising Dopaminergic therapy: particularly if pain is related to motor symptoms or dystonia as excess levodopa may lead to dyskinesia, uncontrolled sudden movement
• Analgesics: Pain medications such as NSAIDs may be used for musculoskeletal pain
• Antidepressants: Neuropathic pain which is common in PD
• Physical Therapy: Aids in managing musculoskeletal pain by addressing postural issues and improving mobility
• DBS for refractory pain