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 |
Fig 6: Large Intestine Sinew Channel Image from Peter Deadman's A Manual of Acupuncture |
Note: In the next entry we will discuss some local needle techniques for the pterygoids.
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