Assessment of Nociceptive Processing Among Patients With Temporo-mandibular Disorders
Condition: Temporomandibular Disorder
MeSH terms: Temporomandibular Joint Disorders; Temporomandibular Joint Dysfunction Syndrome; Mandibular Diseases
Study type: Interventional

Summary: 
      This case control study will investigate the physiological effect of nociceptive input in
      individuals with temporomandibular disorders. To do so, the investigators will compare the
      development of secondary hyperalgesia following high frequency electrical stimulation (HFS)
      of skin nociceptors in the forearms for up to 48 hours in individuals with chronic TMD (as a
      main complain) and in healthy controls. Furthermore, the investigators will evaluate the
      association between the response to HFS and various factors, such as demographic,
      psychosocial and pain-related clinical factors.
    

Detailed description: 
      This control study is designed to compare the development of secondary hyperalgesia following
      high frequency electrical stimulation (HFS) of skin nociceptors in the forearms in
      individuals with chronic TMD (as a main complain) and in healthy controls.

      During the first part of the experiment (time1, day 1), all potential participants will fill
      a basic demographic questionnaire concerning their age, weight, height, and current
      medications (appendix 2). Participants with TMD will be diagnosed according to the Diagnostic
      Criteria for Temporomandibular Disorders (DC/TMD). The DC/TMD includes the following
      questionnaires: the Graded Chronic Pain Scale, the Jaw Functional Limitation scale, the
      Generalized Anxiety Disorder-7, the Patient Health Questionnaire-9 and -15 and the Oral
      Behaviors Checklist. In addition, participants will be asked to fill the Central
      sensitization inventory questionnaire, as well as the symptom Severity Scale. Lastly, the
      investigators will evaluate the distribution of pain by asking participants to draw the pain
      that they felt during the past 7 days on a digital tablet. This will allow us to determine
      the total area of pain of each participant, as well as the Widespread Pain Index. Subjects
      will also be asked to provide a rating of their average pain for the last 24h

      The psychophysical evaluation will be conducted later on the same day (day1). Subjects will
      be asked to provide a rating of their average pain at present time (time 2). Then,
      participants will be familiarized with the different procedures involved in the experiment.

      Pressure pain thresholds will be assessed on the temporalis muscle, the trapezius muscle, and
      tibialis anterior (time 3).

      The intensity of pain resulting from pinprick stimulation and allodynia in the area
      surrounding the electrode ("test area") will be assessed, as well as on the homologous site
      of the contralateral control arm before HFS (time 4).

      Then HFS will be applied (time 5) on the left or right volar forearm (10 cm distal to the
      cubital fossa). HFS will consist in trains of transcutaneous electrical stimuli consisting of
      42 Hz trains (pulse width: 2 ms) lasting 1 s each. The trains will be repeated 12 times. Each
      train will be separated by several 10 seconds of rest. The intensity of each stimulus will be
      set to 5 milliampere.

      The of pain resulting from pinprick stimulation and allodynia in the area surrounding the
      electrode ("test area") will be assessed 30 min after HFS (in a counterbalanced order) on the
      homologous site of the contralateral control arm (time 6).

      The extent of secondary hyperalgesia will be assessed approximately 45 min following HFS
      (time 7).

      Then, they will be asked assess the presence of secondary hyperalgesia in the test-site 24
      (time 8, day 2) and 48 hours (time 9, day 3) following HFS with with calibrated neurological
      examination pins (Neuropen, Owen-Mumford Ltd, Oxford, UK).

      6 months after their initial assessment (time 10, day 180), if they gave their consent for
      long-term follow-up, patients will be asked to fill the following questionnaires again
    

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 milliampere. 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).
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: central sensitization; high-frequency stimulation