The Masseter and Pterygoids and their Channel Relationships

The masseter muscle is one of the muscles of mastication (chewing) and is frequently involved with TMJ pain, but also headaches and other less considered symptoms.  The masseter consists of a superficial, intermediate, and deep layer. All three are on the lateral surface of the mandible and can be palpated directly. The superficial and intermediate layer (considered together) attach from the anterior two thirds of the zygomatic arch to the angle and inferior portion of the ramus of the mandible. The deep layer attaches from the posterior one-third of the zygomatic arch to the superior portion of the ramus of the mandible. Both layers are accessible with an acupuncture needle and several stomach channel points directly traverse this muscle (Fig. 1). The medial pterygoids attach to the angle of the mandible on the medial surface and then attaches to the medial surface of the lateral pterygoid plate of the sphenoid bone. The lateral pterygoids attach to the lateral surface of the pterygoid plate and then to the condyloid process of the mandible (Fig. 3). This blog entry will explore the pain patterns, symptoms, and channel relationships of the muscles of mastication with a primary influence on the masseter and the pterygoids.

Fig. 1: The Masseter in reference to ST-5 - ST-7

Fig 2: Masseter TrPs. Image from Travell and Simons'
Myofascial Pain and Dysfunction: A Trigger
Point Manual

When considering the pain pattern of the masseter muscle, it is best to look at the superficial, intermediate, and deep layer separately. Trigger points in the superficial and intermediate layer refers pain to the lower jaw, teeth and gums and to the maxilla. Trigger points with these referrals usually develop in the region of ST-6. In addition, trigger points might develop in the ST-5 (and posterior to ST-5) region which can refer in an arc across the temple and over the eyebrow. This referral can be a significant contributing factor to headaches, especially when other cervical muscles are referring pain to an overlapping area. This is often seen with a head forward posture as discussed in a previous blog post. In addition to pain, trigger points in the superficial layer of the masseter can cause tooth sensitivity to stimuli such as hot and cold.

The deep layer of the masseter can develop trigger points which can refer to the cheek and TMJ, but often radiate pain deep into the ear. The ear referral is specifically caused by trigger points near the attachment at the zygomatic arch in the region of ST-7. This deep ear referral can be a cause of tinnitus which is usually unilateral, but the masseter can be dysfunctional on both sides, so it can also be bilateral. When bilateral, the patient might report that one side is worse than the other. If the masseter is causing tinnitus, the symptoms will often be aggravated or alleviated with opening the mouth wide as this will stretch the masseter.

As mentioned above, several Stomach channel points (ST-5 – ST-7) directly affect the masseter and can be used as local points. Distal Stomach channel points also can be effective for softening the masseter. ST-44 can be an effective point and looking at actions and indications in Deadman's A Manual of Acupuncture reveals many of the same symptoms described by Travell and Simons in Myofascial Pain and Dysfunction: A Trigger Point Manual. Notably pain in the teeth, pain in the eye, pain in the face, and tinnitus are all indication listed in Deadman for ST-44 which are consistent with trigger point referrals and symptoms of the masseter.  Personally, I find ST-44 a very useful point when there is exquisite sensitivity with palpation at ST-43. Often I will find this on the same side as the symptoms and it will not be as sensitive on the other side nor at similar regions such as LIV-3 or in the other metacarpal spaces. If ST-43 is not sensitive, sometimes ST-40 is very sensitive and feels bruised to the patient, in which case I include this point.

In addition to the Stomach channel, the Large Intestine is frequently used for symptoms associated with dysfunction of the masseter. LI-4 is used by many practitioners and is often combined with ST-44 for tinnitus associated with the masseter, toothpain, and frontal headaches.

However, consideration of LI-6 becomes more interesting. LI-6 is the Luo-Connecting point of the Large Intestine channel and it is at this point that the Luo-Connecting channel separates from the primary channel. The Luo-Connecting channel travels up the arm and, at the angle of the mandible, branches to the ear and to the teeth. Looking at the picture in Deadman (Fig. 5) or the classical description does not indicate depth. It is my opinion that the Luo-Connecting channel does not travel on the lateral surface of the mandible, but on the medial surface. This part of the mandible is really only accessible to palpation with a gloved hand inside the mouth. The muscles that you would be palpating inside the mouth on the medial surface would be the medial and lateral pterygoids. 

Fig. 3: Lateral and Medial Pterygoids. Image from
Netter's Atlas of Anatomy

A couple of interesting things about referrals and symptoms of the pterygoids are worth considering to help bring life to LI-6. First off, the medial pterygoid refers pain deep to the ear and to the throat. This can interfere with swallowing and can contribute to soreness in the throat. In addition, this muscle has an interesting relationship to the tensor veli palatini muscle which, when you yawn or open your mouth, pulls the eustachian tube open and allows drainage and pressure normalization of the middle ear. Tightness of the medial pterygoid can block this function and be a major contributor to ear stuffiness (barohypoacusis) and can contribute to otitis media.

Looking at LI-6 shows indications for dry throat and throat pain. Also, deafness is an indication and this indication is listed as one of the excess conditions in the Great Compendium or Acupuncture and Moxibustion. Many would agree that true deafness is unlikely to be successfully treated with acupuncture, but ear stuffiness and diminished hearing associated with it could potentially be treated, and it is possible that LI-6, via softening and releasing the medial pterygoid muscle, could potentially allow for better drainage and health of the middle ear.

The lateral pterygoids has a very interesting pain referral pattern that first made me consider the connection to the Large Intestine Luo-Connection channel. Notice the similarity between the pain referral as depicted by Travell and Simons and trajectory of the Luo-Connecting Channel (Figs. 4 and 5). In addition, tinnitus and rhinitis are commonly associated with lateral pterygoid dysfunction and these are both indication of LI-6.

Fig. 4: Lateral pterygoid TrP referral pattern.
Image from Travell and Simons' Myofascial
Pain and Dysfunction: A Trigger Point Manual

Fig 5: Large Intestine Luo-Connecting Channel
Image from Peter Deadman's A Manual of Acupuncture

I will often palpate LI-6 when I am working with TMJ dysfunction or any symptoms associated with restriction in the muscles discussed (ear stuffiness or tinnitus that is associated with these muscles, for instance) and include it when it is painful to palpation. When LI-6 is painful to palpation, I find that it is about 50% of the time on the ipsilateral side and 50% of the time on the contralateral side, so it is worth palpating bilaterally. This is not surprising since both the Large Intestine primary and sinew channel cross to the opposite side of the body. I often needle this point by threading the needle parallel to the proximal edge of the abbductor pollicus longus muscle which produces a Qi sensation that travel towards LI-4.

Fig 6: Large Intestine Sinew Channel
Image from Peter Deadman's
A Manual of Acupuncture

For a final thought, since so much muscle anatomy was explored, it is useful to look at the Large Intestine sinew channel. This channel binds at the nose. Much like the Luo-Connecting channel, I believe that this involves the pterygoids which ‘bind’ at the lateral pterygoid plate of the sphenoid bone (Figs. 3 and 6). Much of the Large Intestine sinew channel is more superficial than this, but I believe that the upper portion includes the scalenes and the pterygoids which are on the same myofascial layer. Actually, this portion of the sinew channel is really more obviously on the same myofascial layer as the Lung sinew channel which includes muscles such as the pectoralis minor. LI-6 has an effect on this layer for this very reason, in my opinion, as it is affecting a more Lung sinew channel layer that happens to be part of the Large Intestine sinew channel.


Note: In the next entry we will discuss some local needle techniques for the pterygoids.

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Dry Needling and Acupuncture

I often get asked if I do dry needling. Many acupuncturists become defensive when asked this, and there is currently some contention in the fields of acupuncture and physical therapy, as PTs either have it in their scope of practice to do dry needling (in some states) or are trying to get it added to their scope (in other states, such as Florida). Many acupuncturists feel that dry needling is just another name for acupuncture and that PTs are trying to add acupuncture to their scope.

So, what is dry needling and why is there any controversy? First off, I want to state that this blog post is not intended to state any profession opinion or get into the politics. Instead I am going to discuss the technique, goals, and give a brief history of dry needling.

Dry needling as a technique and name grew out of work primarily from Dr. Janet Travell, MD. Dr. Travell, along with her colleague, Dr. David Simons, MD wrote a very influential two-volume book in the field of pain management called Myofascial Pain and Dysfunction: The Trigger Point Manual. In this book, they discussed trigger points (TrPs) which are defined as hypersensitive spots found in taut bands of muscle (click to read more about TrPs). When palpating muscles that are dysfunctional, there are notable taut bands. Following these taut bands, physicians might find a hypersensitive nodule, often in the belly of the muscle along these taut bands. Pressing these yields hypersensitivity and often a characteristic referral pattern is noted, many times quite a distance from the location of the TrP. These two volume books gave a detailed description of the palpation, signs and symptoms, and pain referral zones of these TrPs for each muscle in the body.

In addition to clinical information regarding locating and diagnosing these TrPs, these books also discussed treatment. Many protocols were discussed, but TrP injections were primary treatments outlined in these books. It became increasingly understood that the mechanism that was at play with TrP injections was the mechanical stimulation from the needle. Most often what was injected were substances such as lidocaine which served the purpose of reducing sensation as a relatively thick hypodermic needle probed into a hypersensitive TrP. Dr. Travell did discuss dry needling, differentiating between using a hypodermic needle to inject a substance versus using a hypodermic needle without injecting a substance (which was, therefore, 'dry-needling'). Over time, especially as acupuncture was becoming more popular in America, other practitioners determined that the use of a thinner solid filiform acupuncture needle could serve the same purpose.

Actually, in the history of acupuncture in China these same techniques were discussed and the Chinese referred to these hypersensitive nodules as Ashi points. Ashi means something along the lines of ‘That’s it’. Imagine a physician palpating for the source of a patient’s pain and the patient proclaims ‘Ashi’. The needle technique involves with needling Ashi points is extremely similar to those described in TrP injection and dry needling circles. Notably this involves locating the hypersensitive nodule, inserting a needle, bringing the needle back to the subcutaneous layer and redirecting the needle. Imagine a needle pointing to numbers on a clock and, from the same point, the needle touches 12, 1, 2, 3, etc. This describes the lifting and thrusting technique discussed in the classics of Chinese medicine. When doing these techniques, there is a characteristic muscle twitch or fasciculation that is achieved as the TrP is being deactivated.

This technique can be extremely effective in reducing pain associated with TrPs which is a very common source of pain. Increasingly, TrPs are being understood to be a major contributor to pain. Needling TrPs with an acupuncture needle is one of the most effective tools to treat these. I feel that acupuncturists are best suited to treat TrPs, as we have the greatest amount of training with needle technique and we have the greatest ability to incorporate this technique into a balanced acupuncture session. However, while all acupuncturists have had some training on needling sensitive points, those who have undergone more continuous training with emphasis on a detailed understanding of anatomy and palpation are going to yield the greatest results. While not all acupuncturists have this understanding, there is growing movement within acupuncture circles to incorporate a more detailed understanding of Western anatomy and utilizing a more integrative approach to treating patients.

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Trigger Points: A Common Cause of Musculoskeletal Pain

In upcoming blog posts I am going to describe common trigger points (often abbreviated as TrPs), discuss their clinical presentation (when it hurts, during which movements, how patients describe the pain, etc.) and pain patterns (where the pain refers to and is experienced by the patient). My goal is to educate patients on common pain patterns and give a few tips on how to prevent and alleviate this pain.

A trigger point is defined by Drs. Janet Travell, M.D., and David Simons, M.D., as a hyperirritable spot in a skeletal muscle that is associated with a hypersensitive palpable nodule in a taut band (a “taut band” is a tight area in a muscle). The spot is painful on compression and can give rise to characteristic referred pain, referred tenderness, motor dysfunction, and autonomic phenomena. This definition is from their excellent two-volume book Myofascial Pain and Dysfunction: The Trigger Point Manual.

Fig.1 Strumming across the fibers of a muscle
to feel taut bands and following it to locate
the TrP. From Travell and Simon's,
Myofascial Pain and Dysfunction

What this definition states is that a TrP in a muscle will be associated with a taut band within this muscle. If TrPs are present in a muscle and you or a practitioner strums across the fiber direction of that muscle, there will be a taut, ropy band that is present. Somewhere within this taut band, usually towards the central belly of the muscle, there will be a palpable nodule which is often exquisitely tender, especially with pressure applied (Fig.1). Usually a minimal amount of pressure will elicit this discomfort, if indeed it is not actively painful with no pressure. In fact, it might be this active pain that brings a patient in for evaluation.

The interesting thing about TrPs is that they have characteristic referral patterns which are where the patient experiences the pain (Fig. 2), either with pressure on the TrP, or, when very active, without. While this pain is sometimes in the vicinity of the TrP, many times it can be quite a distance away. This makes assessment and diagnosis somewhat tricky.

Fig.2 Gluteus Minimus TrP referral pattern which mimics
pain from neural compression causing sciatica.
This is sometimes referred to as pseudosciatica

Motor dysfunction caused by trigger points often involves how this muscle relates to its opposing muscle group (agonist-antagonist). Many times, the presence of TrPs can cause a muscle to become inhibited and it will not be able to perform its job effectively. This might be the case when this muscle, along with certain movements, also helps stabilize a joint.

The last part of the definition refers to autonomic dysfunction. Some TrPs can cause sweating, goosebumps, they can contribute to digestive disturbances, and can even contribute to positional vertigo.

It is important to note that TrPs appear as a result of muscle dysfunction and are not a precise anatomical aspect of a muscle. What I mean by this is that in a healthy muscle, there will be no signs of TrPs. When a muscle is overloaded due to repetitive use, injury, postural tension, stress, and other reasons, TrPs can form. Many times these TrPs can then become a chronic cause of pain.

Finally, while TrPs are very common, there are many other sources of orthopedic pain which can also refer. Spinal nerve impingement, vertebral joint syndromes, tendinopathies and many other conditions need to be taken into account whenever evaluating pain experienced by a patient.

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