Spinal Cord Stimulation for Restless Legs Syndrome

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.

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