Background: A myofascial trigger point is a hyperirritable spot on a skeletal muscle. It is typically marked by a knot that can be felt through the skin. Previous studies suggest that they may be involved in chronic pain disorders, specifically unexplained headaches. The purpose of this study is to review methods to detect myofascial trigger points and their relation to tension-type headaches and migraines.
Findings: Several methods have been used to detect myofascial trigger points (MTrPs) such as ultrasound, microdialysis, electromyography, infrared thermography, and magnetic resonance imaging. Ultrasound is the most promising, but there is no “gold standard” for detection yet. MTrPs are found in both Migraine and Tension-type headache patients. MTrPs are associated with lower pain thresholds, however the pathophysiology is not understood.
Conclusions: MTrPs are found in both tension-type and migraine patients, but the role they play differs between them. It is not well understood how much they differ in their roles.
Tension-type Headaches (TTH) is the most common type of migraine disorder worldwide. This is marked by tenderness and stiffness of the muscles surrounding the head. The term myofascial trigger points was coined in the 1950’s and has come under fire. There have been inconsistencies in the literature describing them or even their existence at all.
Myofascial Trigger points
There are two types: active and latent MTrPs. Active produce pain without touch, and latent only produce pain when palpated. Active points are associated with certain biomarkers that could lead to increased peripheral pain.
Traditional gray-scale ultrasound could identify active MtrPs only 33% of time. So, elastography was tried. This method measures the stiffness of the soft tissue. This provided an identification rate of 100%.
This method measures the concentration of chemicals found both inside and outside the body in active and latent MtrPs. These studies found an increase in all substances compared to other groups.
This is a method used to measure the electrical activity of skeletal muscles. This method showed an increase in electrical activity at rest and during active contraction in MTrPs in comparison to non-affected muscle.
This method measures the temperature of the skin. This method hypothesizes that there is a greater difference in temperature between muscle groups affected by MTrPs and those not affected. This area is largely unhelpful due to low accuracy and decreased research.
Magnetic Resonance Imaging
This method uses an MRI machine to picture the muscles. There were large differences in the number of potential MTrPs identified between clinicians and radiologists. Clinicians tended to identify more, while radiologists identified less when given the same image.
Migraines and MTrPs
There is no agreement on what muscles are most affected or if increased number of MTrPs correlates with increased severity of migraines.
Neck Mobility and Specific Muscles in Migraines
Studies show that the more MTrPs are associated with decreased neck mobility and widespread hypersensitivity to pressure. The quality of the research exploring intervention of migraines by anesthetizing MTrPs is highly questionable. The results are promising, but require proper testing to be trusted.
Tension-Type Headaches and MTrPs
Increased tenderness of the muscles surrounding the head are associated with increased intensity and frequency. MTrPs present in the suboccipital muscles are correlated with increased intensity and frequency of the headache.
Therapeutic Studies Targeting MTrPs
The use of lidocaine injections into MTrPs was explored in 108 patients in a double-blind placebo controlled randomized study. It shows that injection of lidocaine results in a decrease of pain frequency, intensity, and pain medication use. There was also a significant effect on anxiety and depression. A study using another chemical was not as effective and provided no definitive relief.
Ultrasound and EMG appear to be the best methods to detect MTrPs. However the studies on MTrPs and Migraines and Tension-Type headaches are underexplored and lack both quantity and quality. There is no agreement on treatments, causes, which muscles are affected most, if it causes decreased neck mobility, if more MTrPs causes increased frequency and intensity, or if they even exist.
Ultrasound elastography is the most promising tool to identify MTrPs. However, it must still be accompanied with manual palpation. This introduces significant error and bias, so a standard should be created to identify MTrPs. MTrPs are rarely found in control groups without Migraine or Tension-type headache disorders, so their creation and physiology are interesting, but largely unclear with current research. The researchers advise increasing the quality of already done studies before making more other speculations.