Reliability of Measuring the Area and Intensity of Secondary Hyperalgesia Induced by High Frequency Stimulation
Condition: Hyperalgesia, Secondary
MeSH terms: Neoplasm Metastasis; Hyperalgesia
Study type: Interventional

Summary: 
      This study is designed to evaluate the method of assessing the and intensity areas of
      secondary hyperalgesia induced by High Frequency Stimulation (HFS). Measures of the areas of
      secondary hyperalgesia will take place on two experimental days separated by a minimum of two
      weeks. Each experimental day, the areas of secondary hyperalgesia will be assessed three
      times, starting 30 minutes following HFS. Furthermore, the investigators will assess if
      anxiety, catastrophization, stress and demographic variables modulate the extend of
      hyperalgesia.
    

Detailed description: 
      This prospective cohort study is designed to evaluate the method of assessing the areas and
      intensity of secondary hyperalgesia following High Frequency Stimulation (HFS), and will
      consist of two experimental days separated by a minimum of two weeks. During the two each
      session (Day1 and Day2), subjects will go through the HFS procedure on the same forearm.
      Then, after a 30 minutes break, the area and intensity of secondary hyperalgesia induced by
      HFS will be assessed three times (Time9-14), with a two-minute break between each assessment.

      Before the experiment, subjects will fill two questionnaires by email : the Spielberger Trait
      anxiety inventory and the Pain catastrophization scale.The first experimental day, the
      patients will be seated on a chair and informed consent will be gained. Subjects will provide
      demographic information to the researcher (age, gender, size) (Time1). Then, the forearm skin
      of the selected arm will be marked with a pen to improve the precision of subsequent
      measures. The subject will then observe a period of rest for 5 minutes, to provide a baseline
      measure of heart rate variability.

      Next, the patients will be asked to rate the pain induced by pin-prick stimulation in the
      area surrounding the electrode (Time2).

      Following standardized explanation of the HFS procedure, the subject will fill the
      Spielberger State anxiety inventory (Time5), and HFS will be applied on the volar forearm
      (6-10 cm distal to the cubital fossa) (Time6). To avoid any confounding effect of handedness,
      the arm onto which HFS will be applied (dominant vs nondominant) will be counterbalanced
      across participants. In summary, HFS will consist of 12 trains of 42 Hz electrical pulses
      (pulse width: 2 ms) lasting 1 s each. The time interval between each train will 10 s. The
      intensity of stimulation will be 5mA. Heart rate variability during the HFS procedure will be
      monitored.

      After a 25 minutes break the heart rate variability will be assessed a third time during 5
      minutes. During the break, subjects will be asked to stay seated, to fill the Pain
      Catastrophizing scale (short-version) and give a rating from 0-100 for the pain and stress
      experienced during the HFS procedure (Time7).

      Following this break, the area of secondary hyperalgesia will be assessed with a calibrated
      128 mN pinprick probe (The Pin Prick, MRC Systems GmbH, Heidelger, Germany) (Time9). Pokes of
      1-second duration will be provided at a frequency of 0.5 Hz, starting well outside and
      approaching the stimulation site with steps of 0,5 cm from 4 different directions towards the
      application site. Participants will be asked to keep their eyes closed during the entire
      mapping procedure. Then, participants will rate the pain induced by pin-prick stimulation in
      the area surrounding the electrode (Time10). This procedure will be conducted three times,
      with a two-minute break between each assessment (Time 11-14).

      The second experimental day (Day2), the procedure will be similar to the first, but informed
      consent and the Spielberger Trait anxiety inventory and the Pain catastrophization scale will
      not be filled.
    

Intervention name(s): High-frequency electrical stimulation
Intervention type(s): Procedure
Intervention description(s): High-frequency stimulation will be applied on the volar forearm (6-10 cm distal to the cubital fossa). To avoid any confounding effect of handedness, the arm onto which HFS will be applied twice (dominant vs nondominant) will be counterbalanced across participants. HFS will consist of 12 trains of 42 Hz electrical pulses lasting 1 s each. The time interval between each train will be 10 s. The intensity of stimulation will be 5mA. Electrical pulses will be delivered to the skin using a specifically-designed electrode designed: the cathode consists of 16 blunt stainless-steel pins with a diameter of 0.2 mm protruding 1 mm from the base. The 16 pins are placed in a circle with a diameter of 10 mm. The anode consists of a surrounding stainless-steel ring having an inner diameter of 22 mm and an outer diameter of 40 mm. This procedure induces secondary pinprick hyperalgesia (an increase in pinprick sensitivity in a large area of the skin).
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: central sensitization; High-frequency electrical stimulation