Referred Pain
                                =============

þ Referred Pain Causing Referred Inflammation
 - Nociceptors release substance P, which promotes release of histamine from
   mast cells, and contributes to inflammation.
 - Thus, referred pain may cause inflammation and muscle spasm in the are to
   which pain is referred.

þ Myofascial Pain Syndromes
 - pain is referred from a muscular trigger point to a distant area
 - often the muscular trigger point doesn't hurt
 - common sites:
  + sternocleidomatoid -> headache
  + infraspinatus -> anterior shoulder
  + upper trapezius -> neck pain
  + levator scapulae -> neck pain
  + scalene -> shoulder
  + middle trapezius/scalend, or upper paraspinals -> upper back
    [others:  Travell and Simons.  Myofascial Pain and Dysfunction:  The
    Trigger Point Manual.  Williams & Wilkins, Baltimore, 1983.]
 - Commonly misdiagnosed 
 - Almost always some "perpetuating factor," such as always sitting in a
   particular position, that keeps the myofascial pain going.
 - Can elicit with pressure of about 3-4 kg/cm squared over the offending
   trigger point.
 - Treatment:
  + better posture
  + heat + stretching of the specific trigger-point muscle
  + OTC analgesics to start with
  + "spray and stretch" (ethyl chloride sprays, 3 sprays at one-minute
    intervals while stretching, alternating with moist heat)
  + if this fails, try a PT referral
  + if this fails, inject trigger point with 0.5-1.0 cc of local anaesthetic
    (Skootsky recommends procaine, I'd use bupvicaine)  HOWEVER, don't use
    trigger point injection as main first treatment; will fail unless other
    factors managed, too.
[Skootsky SA, Jaeger B, Oye RK. West J Med 1989;151:157.].