Within spinal pain , patients with neck pain were found to have the highest prevalence rates of MTrPs .
The trapezius descendens , levator scapulae , and suboccipitales muscles were the most prevalent locations for active MTrPs in patients with neck pain .
Latent MTrPs were present in asymptomatic people , but no significant differences were found in the prevalence rate of latent MTrPs between patients with spinal ( neck ) pain and healthy controls .
The only study investigating prevalence of MTrPs in different localizations of the same muscle reported no significant differences in prevalence between active and latent MTrPs within the trapezius descendens muscle .
Studies examining pathophysiological mechanisms underlying MTrPs demonstrated an acidic environment , high concentration of algogenic/inflammatory substances , stiffer muscle tissue , retro grade diastolic blood flows , spontaneous muscle activity at rest , and loss of muscle contractibility in muscles with MTrPs .
Altered central processing was also found to play a role in the development of MTrPs .
Myofascial trigger points are a prevalent clinical entity , especially in patients with neck pain .
Evidence was not found to support or deny the role of MTrPs in other spinal pain .
Compelling evidence supports local mechanisms underlying MTrPs .
OBJECTIVE A systematic review was performed to evaluate the existing evidence related to the prevalence , incidence , localization , and pathophysiology of myofascial trigger points ( MTrPs ) in patients with spinal ( back and neck ) pain .
Bilateral Activation of Motor Unit Potentials with Unilateral Needle Stimulation of Active Myofascial Trigger Points
Audette JF , Wang F , Smith H : Bilateral activation of motor unit potentialswith  unilateral needle stimulation of active myofascial trigger points . Am J Phys Med Rehabil 2004;83:368–374 . Objective : The objective of this study was to determine if there are electromyographic differences between active and latent myofascial trigger points ( MTrPs ) during trigger point needling . Design : A total of 21 subjects were recruited prospect ively . The experimental group consisted of 13 subjects who had active myofascial pain in the neck for > 6 mos . The age-matched , control group consisted of eight subjects without neck pain but with taut b and s in the cervical musculature . The active MTrPs ( or latent MTrPs in the control group ) were identified in the trapezius or levator scapulae muscles , then needle electrodes were inserted ipsilaterally into the muscle with the MTrPs and into the same muscle on the contralateral side . Electromyographic activity was recorded bilaterally with a dual-channel electromyographic machine , and local twitch responses were obtainedusinganacupuncturedryneedlingtechniqueonlyonthesideoftheactiveMTrPs . Results : We demonstrated that in subjects with active MTrPs , bilateral motor unit activation could be obtained with unilateral needle stimulation of the trigger point . In contrast , in all the subjects with latent MTrPs , only unilateral motor unit activation could be obtained in the muscle on the same side of the needle stimulation . The motor unit potentials seen on the electromyograph were similar in morphology to a fasciculation potential but more complex . Conclusion : We demonstrated bilateral or mirror-image electromyographic activity associated with unilateral needle stimulation of active MTrPs . We have found no previous mention of this phenomenon in the literature . Our study supports the concept that the perpetuation of pain and muscle dysfunction in active MTrPs may be related to abnormal central nervous system processing of sensory input at the level of the spinal cord
Within spinal pain , patients with neck pain were found to have the highest prevalence rates of MTrPs .
The trapezius descendens , levator scapulae , and suboccipitales muscles were the most prevalent locations for active MTrPs in patients with neck pain .
Latent MTrPs were present in asymptomatic people , but no significant differences were found in the prevalence rate of latent MTrPs between patients with spinal ( neck ) pain and healthy controls .
The only study investigating prevalence of MTrPs in different localizations of the same muscle reported no significant differences in prevalence between active and latent MTrPs within the trapezius descendens muscle .
Studies examining pathophysiological mechanisms underlying MTrPs demonstrated an acidic environment , high concentration of algogenic/inflammatory substances , stiffer muscle tissue , retro grade diastolic blood flows , spontaneous muscle activity at rest , and loss of muscle contractibility in muscles with MTrPs .
Altered central processing was also found to play a role in the development of MTrPs .
Myofascial trigger points are a prevalent clinical entity , especially in patients with neck pain .
Evidence was not found to support or deny the role of MTrPs in other spinal pain .
Compelling evidence supports local mechanisms underlying MTrPs .
OBJECTIVE A systematic review was performed to evaluate the existing evidence related to the prevalence , incidence , localization , and pathophysiology of myofascial trigger points ( MTrPs ) in patients with spinal ( back and neck ) pain .