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11 Articles in Volume 21, Issue #1
Advanced Practice Matters with Theresa & Jeremy: Mentorship
Ask the PharmD: What is a true opioid allergy?
Behavioral Medicine: How Clinicians Can Reduce the Stigma Attached to Chronic Pain
Cardiovascular Disease and COVID-19 Infection: A Look at Long Haulers
Chronic Headache: How to Conduct a Virtual Neurological Examination
How COVID Has Changed Pain Practice and Policies
How to Conduct a Pain Evaluation Using Telemedicine
Inside the Potential of Biologics for the Treatment of Rheumatoid Arthritis
Managing Pain in Parkinson’s Disease
Spinal Cord Stimulation Shown to Improve Pain and Movement in Parkinson’s Disease
TeleRheumatology Before and During the COVID-19 Pandemic

Spinal Cord Stimulation Shown to Improve Pain and Movement in Parkinson’s Disease

The search to relieve the symptoms of Parkinson’s Disease continues with the investigation of SCS as both singular bioelectric therapy and salvage therapy after the loss of efficacy of deep brain stimulation.

A recently published study shows that spinal cord stimulation (SCS) relieves pain and improves motor symptoms in patients with Parkinson’s disease (PD) who have and have not received deep brain stimulation (DBS) therapy.1 PD is a progressive, multisystem neurodegenerative disease that leads to motor symptoms, such as tremor, bradykinesia, rigidity, and postural instability, and non-motor symptoms, including pain, orthostatic hypotension, urinary disturbances, sleep disorders, and various neuropsychiatric symptoms, all of which have a significant impact on quality of life.

Parkinson’s disease has an incidence of 0.1% to 0.2% in those over the age of 40 and a prevalence of more than 1 million people in  North America.2 The transition from disease impairment to loss of independent function generally occurs between 3 and 7 years after the onset of PD, and management includes targeting the impairments caused by the disease.3

Spinal cord stimulation may have the potential to alleviate both motor and non-motor symptoms of Parkinson's disease. (Image: iStock)

Pathophysiology of Parkinson's Disease is Still Unknown

While the cause of PD is still being studied, two markers have been identified that underlie the pathophysiology of the disease process:

  • the degeneration of dopaminergic neurons in the nigrostriatal pathway
  • the presence of Lewy bodies in surviving neurons.1

The degeneration of dopaminergic neurons leads to reduced inhibition of the thalamus and decreased excitatory input to the motor cortex, resulting in bradykinesia and other PD symptoms. The decrease in dopaminergic neural firing in the nigrostriatal pathway may disrupt the neural oscillations in the basal ganglia and lead to disordered firing of neurons in the motor system.4

Dopamine replacement therapy and DBS, which can directly disrupt the disordered oscillations in PD, are thus the primary modes of management.3 However, dopamine and DBS therapy, the gold standard treatments for PD, continue to have severe limitations and side effects. Dopamine agonists lose their efficacy over time and are associated with such side effects as  dyskinesias, GI disturbances, orthostatic hypotension, and neuropsychiatric features including anxiety and hallucinations.5,6 DBS carries risks of intracranial bleeding, hardware issues, infection, incorrect placement, mis-positioning, and seizures.7 It also may show decreased efficacy over time.8

SCS may have the potential to alleviate both motor and non-motor symptoms of PD. Stimulation of the dorsal columns within the epidural space has already demonstrated benefit in numerous pain conditions and research has shown its ability to improve gait dysfunction in advanced PD.9,10 Studies also have shown the utility of SCS as a salvage option after dopamine and DBS have failed.11 SCS is associated with increased risks of hematoma, infection, seroma, and, rarely, epidural hemorrhage.  

Parkinson's-Related Pain Scores Significantly Improved with SCS

In this most recent study, Krishnan V. Chakravarthy, MD, PhD, a pain management specialist at the University of California San Diego Health Center, and his team recruited 15 patients who either had chronic pain of predominantly neuropathic origin that was refractory to analgesic drugs and nerve blocks, or whose pain had not improved following adequate dopaminergic drug therapy or DBS.1 The causes of pain included:

  • lumbar spine surgery (5 patients)
  • radicular pain due to compression fractures (4 patients)
  • radicular pain due to severe spinal scoliosis (1 patient)
  • postural abnormalities (3 patients)
  • unknown etiology (2 patients).

The patients had an average age of 74 years and an average PD duration of 17 years.1

One or two percutaneous electrodes were implanted in the epidural space on the dorsal midline at the level of the thoracic or cervical spine and connected to an implantable pulse generator. Devices were set to one of three stimulation modes according to patient preferences: continuous tonic stimulation, continuous burst stimulation, or cycle mode with burst stimulation. Most patients chose the burst modalities.1

All patients experienced significant improvement in VAS pain scores after implantation of SCS with a mean reduction of 59% (P < 0.005). For patients who did not receive DBS prior to SCS (n=7), the average percent reduction was 57%, and for those who did receive DBS (n=8), the average percent reduction was 61%. Those who chose the cycling burst stimulation parameter experienced an average 67% reduction in VAS scores, while the continuous burst parameter group showed an average 48% reduction.1

Parkinson's Motor Function Improvements Are Not as Clear with SCS

Few studies have examined whether SCS can lead to improvement in motor function and concurrent pain in patients with PD. In Chakravarthy’s study, 14 of the 15 patients had SCS implanted in the thoracic epidural space.1 (See also, SCS for chronic pancreatitis)

A previous case report showed that placement at that level (T9-10) led to improvement in motor function. Improvements in motor function occurred, although the differences were not statistically significant; 73% of patients experienced improvements in the 10-meter walking test, with an average improvement of 12%. For the Timed Up and Go (TUG) test, 64% of patients experienced clinically relevant improvements, with an average improvement of 21%. However, given the study design, it was not possible to determine whether the motor effects stemmed from the effects of SCS or if the decrease in pain allowed the patients to improve their motor testing results.

“[Our] study thus points to the potential utility of SCS as an option to address both pain and motor symptoms in PD patients who have and have not received DBS therapy,” said Dr. Chakravarthy. The mechanism has not been completely elucidated, however. Electrical stimulation of the spinal cord may send signals to basal ganglia circuits that then increase the release of stored dopamine.12 SCS may also serve a neuroprotective function that delays the progression of dopaminergic neuron loss in the brain. Additional research is needed to explore the efficacy of SCS placed in the thoracic epidural space, as well as the causal relationship between SCS, pain, and motor improvement.2

Data are lacking on the potential synergistic effects of SCS and DBS in patients with PD regarding improvements in gait and postural instability. It is possible that the two approaches together could stimulate multiple complementary neuronal areas, thus improving patients’ movement ability.

The types of stimulation pattern and frequency are also being studied. More research is needed to determine maximal efficacy at different spinal levels and mode of stimulation. “We believe that the data in this study can be helpful to guide future studies that utilize SCS as salvage therapy for Parkinson’s disease to improve the body of literature on the use of SCS in PD patients,” concluded Dr. Chakravarthy.

 

See also, managing dementia and psychosis in patients with Parkinson's on our sister site.

Last updated on: January 22, 2021
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