Peripheral Nerve Stimulation for Shoulder Pain: Dose Response
Condition: Stroke; Shoulder Pain
MeSH terms: Shoulder Pain; Stroke
Study type: Interventional

Summary: 
      The primary objective of this RCT is explore the mechanism for Hemiplegic Shoulder Pain (HSP)
      reduction due to treatment with peripheral nerve stimulation. We will explore the association
      of subject-specific clinical and demographic information and pain relief from PNS. We will
      explore the possible role of central sensitization mechanisms in perpetuating pain via
      measures of sensory and pain perception. Lastly, we will explore the dose-response
      association of muscle-contraction from PNS and pain reduction, completion of activities of
      daily living (ADLs), and improvement in quality of life.
    

Detailed description: 
      Hemiplegic shoulder pain (HSP) affects up to 60% of moderate to severely impaired stroke
      survivors. HSP is associated with poor rehabilitation outcomes, including interference with
      activities of daily living (ADLs) and poor quality of life (QoL). While many treatments for
      HSP have been proposed, most do not result in long-term relief of pain.

      The investigators developed the use of intramuscular peripheral nerve stimulation (PNS) for
      the treatment of HSP, which involves the temporary placement of a percutaneous intramuscular
      electrode to stimulate the axillary nerve motor points to the deltoid muscle. The deltoid
      muscle is stimulated for 6 hours per day for 3 weeks, causing comfortable, non-fatiguing
      contractions. This treatment, which occurs in the community setting, results in pain relief
      for up to 12 months when compared to treatment with a hemisling. A systematic review of
      randomized controlled trials (RCT) with pain as the primary outcome concluded that
      intramuscular PNS was the only treatment to provide long-term relief of pain for those with
      HSP. We have completed two RCTs that have demonstrated that a short-term PNS treatment (i.e.,
      3 or 6 weeks) provides pain relief. The first trial demonstrated efficacy in long-term pain
      relief in more than 60% of subjects for greater than 12 months. The second trial corroborated
      the finding that more than 60% of subjects receiving PNS achieved long-term pain reduction,
      and also showed that PNS reduces pain more than that achieved with physical therapy. The
      mechanism of action of PNS in reduction of HSP is not yet known. Thus, the primary objective
      of this RCT is explore the mechanism for HSP reduction.

      The mechanisms behind PNS for the treatment of HSP are not known. First, individual variation
      may contribute to response to PNS, thus we will explore the association of subject-specific
      clinical and demographic information and pain relief from PNS. Secondly, our team and others
      have found that in the chronic stage central sensitization mechanisms may also have a role in
      perpetuating pain, as it does in other forms of chronic shoulder pain. These mechanisms will
      be explored via measures of sensory and pain perception. Finally, our approach to delivering
      PNS for HSP is different from other treatments in which PNS is delivered through skin surface
      electrodes (e.g., transcutaneous electrical nerve stimulation or TENS) in that our treatment
      produces repeated muscle contraction over the course of weeks. Treatments such as TENS
      generates tingling sensations (paresthesias) over the painful area, and pain relief following
      stimulation is short-lived, seldom lasting more than a few hours. We postulate that long-term
      pain relief for HSP after PNS treatment is due to the repeated muscle contraction that occurs
      daily over the course of treatment, thus we will explore the dose-response association of
      muscle-contraction from PNS and pain reduction, completion of activities of daily living
      (ADLs), and improvement in quality of life.
    

Intervention name(s): Peripheral Nerve Stimulation
Intervention type(s): Device
Intervention description(s): The stimulation system includes an external stimulator, percutaneous lead and pad. The stimulator snaps onto the pad. The pad has an embedded power source but also serves as the anode. The 1-channel stimulator outputs a biphasic current waveform with current pulse parameter ranges suitable for PNS. The percutaneous lead is inserted using an introducer (like a hypodermic needle) which is withdrawn and the lead is retained in the muscle by a barb at its tip. After a 1-week stabilization period, stimulation is initiated (daily dose is Group-dependent). Stimulus parameters may be adjusted by the research staff as deemed appropriate. The treatment period is 3 weeks after which the lead will be removed. Total time of electrode implantation is no more than 29 days.
Other intervention name(s): Intramuscular Peripheral Nerve Stimulation; Intramuscular Electrical Nerve Stimulation; Smartpatch System
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Stroke; Shoulder Pain; Electrical stimulation; Neuromuscular stimulation; Intramuscular stimulation