Spinal Cord Stimulation for Restless Legs Syndrome

Not Applicable

Completed

Conditions: Restless Legs Syndrome
Neuropathic Pain

Interventions: Diagnostic Test: Dual-energy X-ray absorptiometry Scan
Other: Continuous Blood Pressure
Other: Laboratory Measurements
Behavioral: Continuous Blood Pressure Diary
Other: Blood Flow Measurement
Other: Partial pressure of oxygen
Other: Microneurography
Other: Anthropometric Measurements
Behavioral: John Hopkins Restless Legs Severity Scale

Registration Number: NCT03539081

Lead Sponsor: Marshall Holland

Brief Summary: The overall goal of this proposed study is to evaluate the underlying mechanisms of neural control of blood flow in the lower extremities in humans with restless leg syndrome (RLS). At least 15% of the general public suffers from RLS and many more may go undiagnosed. This unfortunate disorder leads primarily to a disturbing sensation within the patient's lower extremities that requires movement for relief (1, 2). The central hypothesis of our study is that physiological changes in lower limb blood flow as a result of thoracolumbar epidural Spinal Cord Stimulation (SCS) lead to the relief of RLS.

Detailed Description: Patients age 18-85 years with (n=25) and without RLS (n=25) that have recently having undergone Spinal Cord Stimulation (SCS) implantation (thoracolumbar) for chronic pain will be recruited from the Departments of Anesthesia and Neurosurgery, University of Iowa Hospitals and Clinics. The rationale for studying both RLS patients and non-RLS patients with chronic back pain is to initially test the effectiveness of Spinal Cord Stimulation (SCS) on lower limb blood flow in the absence of symptoms of RLS. In the non-RLS patients, we could determine if SCS does in fact alter limb blood flow. We hypothesize that RLS patients have altered muscle sympathetic nerve activity (MSNA) and blood flow correlating to severity of RLS symptoms, which will then be modulated by Spinal Cord Stimulation (SCS), allowing for resolution of symptoms in RLS with MSNA-mediated improvements in leg blood flow. We also hypothesize that SCS in RLS patients will reduce 24-hour ambulatory blood pressure in parallel with reductions in MSNA.

Those deemed eligible to participate will be invited for 2 visits to the Translational Vascular Physiology Laboratory in the Clinical Research Unit (CRU) of the University of Iowa Hospitals and Clinics. Each of the 2 study visits are identical except for experimental measurements that are made at each of the five measurement time points when the Spinal Cord Stimulation (SCS) unit is either on or off as described below.

Visit 1: Experimental measurements include non-invasive "gold standard" measures of limb blood flow and arterial stiffness including femoral artery blood flow via Doppler ultrasound, calf blood flow from strain gauge venous occlusion plethysmography, and arterial stiffness via pulse wave velocity using applanation tonometry. Additionally, participants will be asked to assess the current level of leg discomfort every 10 minutes while measurements are taken by the SIT test, a validated technique for assessing restless legs symptoms where patients are asked to set and rest quietly during measurement talking, moving as little as possible (3).

Visit 2: Experimental measurements include direct measures of sympathetic nerve activity using microneurography before, during and again after administration of SCS to the patient. Additionally, participants will be asked to assess the current level of leg discomfort every 10 minutes while measurements are taken by the SIT test, a validated technique for assessing restless legs symptoms where patients are asked to set and rest quietly during measurement taking, moving as little as possible (3).

Some participates may visit the laboratory for placement of a 24-hour ambulatory blood pressure cuff.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 15

Inclusion Criteria

Mental capacity to understand and decide to participate in the research
Recently have undergone or are planning to undergo SCS implantation (thoracolumbar region) for chronic pain.

Exclusion Criteria

Peripheral vascular disease
History of ischemic heart disease ( examples myocardial infarction, cardiac bypass surgery, coronary stent, unstable angina)
Heart transplantation
Renal Failure
Congestive heart failure
Type 1 diabetes
Pregnancy

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Subjects with RLS	Blood Flow Measurement	Subjects with Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects without RLS	Laboratory Measurements	Subjects without Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects with RLS	Partial pressure of oxygen	Subjects with Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects with RLS	Anthropometric Measurements	Subjects with Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects without RLS	Partial pressure of oxygen	Subjects without Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects with RLS	Laboratory Measurements	Subjects with Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects with RLS	Dual-energy X-ray absorptiometry Scan	Subjects with Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects with RLS	John Hopkins Restless Legs Severity Scale	Subjects with Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects without RLS	Blood Flow Measurement	Subjects without Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects with RLS	Microneurography	Subjects with Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects without RLS	Dual-energy X-ray absorptiometry Scan	Subjects without Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects without RLS	Anthropometric Measurements	Subjects without Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Continous BP Monitoring	Continuous Blood Pressure	This arm consists of subjects from arm "Subjects with RLS", "Subjects without RLS", and the rest of the qualifying subjects undergoing continuous blood pressure portion of the study only. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Subjects without RLS	Microneurography	Subjects without Restless Leg Syndrome that have recently undergone Spinal Cord Stimulation (SCS) Implantation for chronic pain. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.
Continous BP Monitoring	Continuous Blood Pressure Diary	This arm consists of subjects from arm "Subjects with RLS", "Subjects without RLS", and the rest of the qualifying subjects undergoing continuous blood pressure portion of the study only. Subject will have received the standard of care intervention of epidural spinal cord stimulation for pain.

Primary Outcome Measures

Name	Time	Method
Response Measurement of Thoracolumbar Epidural SCS in the Femoral Artery Blood Flow	Baseline and 1.5 Hours	The response will be measured by Doppler ultrasound of the femoral artery during epidural spinal cord stimulation in patients with chronic back pain.
Percent Change MSNA Burst Frequency From Baseline to 60 Minutes	Baseline to 60 minutes	Response will measured by peroneal nerve microneurography to the lower limb during epidural spinal cord stimulation in patients with chronic back pain. Percent change MSNA burst frequency from baseline to 60 minutes

Secondary Outcome Measures