The Natural History of Upper Trapezius Myofascial Trigger Points: Comparison of Local and Remote Tissue Milieu in Normal Muscle, Latent and Active Myofascial Trigger Points Over Time
Condition: Neck Pain
MeSH terms: Neck Pain
Study type: Observational

Summary: 
      This study will use microdialysis to investigate myofascial pain. This pain is characterized
      by "trigger points" (exquisitely tender spots) in a group of tense muscle fibers that extend
      from the trigger point to the muscle attachments. Trigger points in the trapezius, a large
      muscle lying between the neck and shoulder, are typically caused by emotional stress,
      postures such as hunching shoulders, certain activities like using a telephone receiver
      without elbow support, or by wearing certain articles such as a heavy coat or heavy purse.
      Microdialysis uses a very thin needle probe (about the size and shape of an acupuncture
      needle) to collect and measure chemicals directly from soft tissue. Analysis of these
      chemicals will show whether changes in the tissue around a muscle with trigger points are
      confined to that muscle, or if these changes also occur in more distant muscles.

      The study will examine two types of trigger points. An "active" trigger point causes pain or
      other abnormal symptoms and often causes problems with movement. A "latent" trigger point
      often causes movement problems without causing pain. Many healthy adults have latent trigger
      points.

      People between 21 and 65 years of age with the following characteristics may be eligible for
      this study: 1) no neck pain or trigger points in either upper trapezius muscle; 2) no neck
      pain but a latent trigger point in at least one upper trapezius muscle; or 3) neck pain of
      less than 3 months' duration and an active trigger point in at least one upper trapezius
      muscle. Participants undergo the following procedures:

        -  Physical examination of the muscles of the neck and shoulder area, testing strength and
           range of motion, and response to palpation to find trigger points.

        -  Pain inventory. Subjects complete a questionnaire for measuring pain and its intensity,
           location, quality, causes, relievers, and associated symptoms. The questionnaire is
           filled in before and after each microdialysis procedure.

        -  Microdialysis in upper trapezius muscle. An electrode patch is placed on either side of
           the site for insertion of the microdialysis probe and another electrode is placed on the
           outer edge of the shoulder. The electrodes are used to measure any electrical activity
           that occurs with insertion or movement of the probe. The subject lies face down and the
           probe is inserted in the upper trapezius muscle. It remains in place for 5 minutes while
           chemical substances are collected from the muscle. It is then advanced about 1.5 cm
           deeper into the muscle until a twitch response is obtained and remains in place for 10
           more minutes while substances are collected.

        -  Microdialysis in the gastrocnemius muscle (large muscle of the calf). The same procedure
           for the upper trapezius muscle is done in the calf muscle.
    

Detailed description: 
      Preliminary data suggest that patients with active myofascial trigger points (MTrPs) have a
      significantly different biochemical profile within the local milieu of the MTrPs compared to
      those without MTrPs or those with a latent (non-symptomatic) MTrP. An important question to
      answer is whether anatomical loci, remote from active or latent MTrPs have similar
      biochemical profiles to the MTrP itself. These remote sites should be evaluated to help
      distinguish whether MTrPs have local biochemical profiles or are associated with a more
      widespread phenomenon.

      We will select three groups of subjects based on the following characteristics [1, 2, 3
      below]. We will sample GB-21 in the upper trapezius muscle and LV-7 (posterior and inferior
      to the medial condyle of the tibia in the upper portion of the medial gastrocnemius)
      standardized sites for pH, muscle metabolites, inflammatory mediators, arachidonic acid
      derivatives, neuropeptides, etc.

      The goal of this study is to determine whether the local biochemical milieu of an active MTrP
      is the same as the biochemical milieu at anatomical sites remote from the MTrP.

      The acupuncture points GB-21 and LV-7 are selected specifically to standardize the locations
      of a sampling point in three carefully selected groups:

        1. healthy subjects without neck pain and who have no MTrPs identified by palpation
           bilaterally in GB-21, and who have no MTrPs identified by palpation bilaterally in LV-7,

        2. healthy subjects without neck pain in whom latent MTrPs are identified by palpation in
           GB-21 in one of the upper trapezius muscles, and who have no MTrPs indentified by
           palpation bilaterally in LV-7,

        3. healthy subjects complaining of neck pain of less than 3 months duration with active
           MTrPs identified by palpation in GB-21 in one of the upper trapezius muscles, and who
           have no MTrPs identified by palpation bilaterally in LV-7.
    

Keywords: Pressure Pain Threshold; MTrP; Musculoskeletal Pain; Soft Tissue Pain; Pathophysiology; Myofascial Pain; Microdialysis; Myofascial Trigger Points; Rehabilitation; Muscle Pain; Neck Pain; Healthy Volunteer; HV; Normal Control