Sternoclediomastoid Muscle Trigger Point and Fascia Pain. Hypertonic SCM's Create Serious Symptoms. Learn SCM Anatomy, Fascia, SCM Trigger Points, and Healthy Neck Curvature Here.
- Tara Lee Clasen
- 3 days ago
- 9 min read
Updated: 3 hours ago
Those with chronic neck pain have heightened electrical activity in their sternocleidomastoid muscles. Electrical signals trigger muscle fibers to contract. On the front of the neck, the sternocleidomastoid is a prominent neck muscle, easily seen when someone turns their head to the side. This muscle is named after its attachment sites: the sternum, the clavicle, and the mastoid, and people refer to it as SCM for short.
Head posture, sleep positions, the vagus nerve, breathing patterns, other neck muscles, the surrounding fascia and the other muscles and structures of the neck affect the SCM.
This blog post will teach you about the anatomy of the sternocleidomastoid and its trigger points. Trigger points refer pain to other areas, i.e. pain at the top of the head originating from the front of the neck. This post will also explain how entire body posture affects the SCM, the movements of the SCM, the SCM as a stabilizing force, and touch on proper neck curvature, as affected by the SCM.
In my practice, I treat women with headaches, migraines, ear pain, eye pain, jaw pain, throat tension, dizziness, and a variety of pain patterns in the face, neck, and head. For some women, even at that very first appointment, when they learn about trigger points, the mystery of the anatomy, how the breath affects their necks, and what else creates the symptoms that they have, they find relief. Most of these women have undergone many types of appointments, tests, and even MRIs but still have no answers.
To learn more about the scalanes muscles, which affect the sternocleidomastoid muscle, head HERE
To learn more about the connection of the lymphatic system, the vagus nerve, the immune system, and the SCM muscles, access a post HERE (COMING SOON!--I LOVE this post!).
And to learn about all the different symptoms the SCM can create in the mind-body click HERE (I also LOVE this post!).
Wondering whether SCM trigger points are causing you pain?
Scroll to the end of this post to see the SCM trigger points!
Fascia
Fascia is rich and responsive and profusely innervated. Fascia contains proprioceptors and nociceptors. Proprioceptors allow for your body’s awareness of where it is in space, and nociceptors are special sensory neurons that sense and respond to damaging stimuli. Fascia is a vast network of communicat
ion, surrounding, protecting, and communicating with everything inside your body. Fascia is also a vast network of strength. It affects your muscles’ ability to slide and glide and gives your soft tissue shape and structure.
The Deep Cervical Fascia
Multiple layers make up the deep cervical fascia. There will be more posts about just fascia COMING SOON!
This fascia surrounds the entire neck like a collar. The “investing layer” of the deep cervical fascia covers the entire neck, but it splits and fully envelopes the SCM and trapezius; muscles on the front and back of the neck. This fascia attaches to the hyoid bone, ligamentum nuchae, occipital bone, temporal bone, external acoustic meatus, zygomatic arch, the mandible, the tympanic plate, the scapula, the clavicle, and the manubrium. It blends with the masseter muscle and forms part of the stylomandibular ligament.
So here we have this noticeable, large neck muscle that is specially enveloped by the deep cervical fascia, and that fascia also touches everything else in the neck.
When the SCM muscle and the fascia at the level of the SCM are tight and tense, it is going to talk to the fascia that is surrounding everything else. Consider this when thinking of your chronic neck pain and the symptoms in your face, ear, and head.
The Sternocleidomastoid and the Vagus Nerve
At the level of the neck, the whole cervical sleeve is affecting the vagus nerve. Forward head posture, a stressed cervical spine and C-1, a loss of cervical curvature, and tight fascia and muscles hurt the vagus nerve, which is on the front of the neck. It is behind the SCM and has a special relationship with it. To learn more, check out my other posts.
The Anatomy of the Sternocleidomastoid
The SCM is a long, two-headed, bilateral muscle. Two-headed means there are two places of origin, and then muscle comes together, and has signaler points of insertion. Bilateral means there are two muscles, one on each side of the neck.
The two muscles can both be dysfunctional, but normally one is more problematic than the other. Please see the section below on “The SCM and Whole Body Posture.”
SCM Origin, Insertion, Artery, and Nerve Supply
Each muscle has an origin and an insertion. The muscle action comes from these ends moving closer together. As mentioned, the SCM has two heads. One head originates from the manubrium of the sternum, and the second head originates from the medial third of the clavicle. The two heads join to form a singular muscle belly and insert onto the lateral surface of the mastoid process of the temporal bone and the lateral half of the superior nuchal line of the occipital bone.
You may feel the carotid pulse at the middle front of the muscle. The vagus nerve is closely behind the SCM, but there are other structures that also run behind it.
Neurovascular bundles can be superficial or deep. Superficially, neurovascular bundles are structures that bind nerves and veins with connective tissue. Right behind the SCM is a neurovascular bundle that includes the common carotid artery, the internal jugular vein, the vagus nerve, and the cervical ansa.
Compressing these structures would cause a variety of problems, including brain fog.
SCM Anatomical Details
Origin
Sternal head: superior part of anterior surface of manubrium sternum
Clavicular head: superior surface of the medial third of the clavicle
Subcutaneous tissue of infra-clavicular and supraclavicular regions
Insertion
Lateral surface of the mastoid process of the temporal bone. Lateral half of the superior nuchal line of the occipital bone.
Artery
Occipital artery and the superior thyroid artery
Nerve
Spinal accessory nerve (CN XI) (motor supply) and branches of cervical plexus C2-C3 (sensory supply) and anterior rami of C2 and C3 (proprioceptive supply).
The Actions of the SCM
Your head moves dynamically, at many angles, many degrees of flexion, extension, and rotation. Your two SCMs both always stabilize your neck, but the movement of the neck depends on whether one muscle is contracting or if they both are. Reading about the actions of the SCM can seem more confusing than reading about the actions of other muscles. You can see the SCM’s functional movement when the head turns to look over the shoulder or when you pick your head up from a lying position.
The short way to talk about SCM movement is this:
The SCMs perform head rotation, lateral flexion (tilting the head), neck flexion (chin to chest), and head extension (from a flexed position).
Here is more detailed information about the movements of the SCM. Check out the “Little-Known SCM Movements” section below to learn more.
Unilateral Contraction
Unilateral contraction means one SCM is the contracting force. Please keep in mind that the other SCM will still work, stabilizing the neck.
Ipsilateral Flexion
When one side contracts, the head moves into ipsilateral flexion. The head will tilt towards the same side as the SCM that is contracting. The mastoid process (the skull behind the ear) moves closer to the shoulder.
Contralateral Rotation
When one SCM contracts, the head moves into contralateral rotation. This means that the head can turn towards the opposite side of the SCM that is contracting. This can be difficult to understand. But if you rotate your head to the left, and side-eye yourself in the mirror, you will see the right SCM clearly visible (because it is contracting).
Bilateral Action
Bilateral action means that both SCM muscles are contracting.
Neck Flexion
When both SCMs contract, the chin moves down and the neck flexes. When both SCMs contract, the head moves forward (over the shoulders).
Head Extension
The SCMs will also bring the neck back to a neutral or extended position when the neck is already flexed. The SCM only aids in neck extension (grossly…it is always stabilizing) when the head is already in flexion. This again shows the dynamic stabilization and movement of the SCM.
Little-Known Actions of the SCM
The SCM also senses and stabilizes the needs of the head and jaw during eating and drinking.
In my practice, I find some people pair talking and neck tension. This means that the neck tenses more than needed when in conversation. I believe SCM tension is also sensing jaw movement when talking, and in these people, there is a relationship with jaw tension and anterior neck tension that can have an emotional component. This could be the emotion of anxiety, a learned response of “trying to be heard,” or an element of "trying not be too vocal".
The SCM also assists in breathing, but not in the way the scalene muscles do (head HERE to learn about the scalene muscles). The SCM involves itself in breathing during deep inspiration or labored breathing. People with prolonged or chronic respiratory stress will have tense or even overdeveloped SCM muscles.
The SCM's ability to lift the ribcage also means that when the muscle is tight or overdeveloped, it can pull the ribcage up, contributing to issues with rib flare and poor diaphragm breathing. Conversely, if we are not correctly using our diaphragm, the neck muscles will overwork as they attempt to assist is elevating the ribcage (trying to get in more air).
SCM and Its Role in Stabilization
When the SCM is constantly overworked, various symptoms will appear. And again, the SCM isn’t just contracting to move the neck; the SCM is stabilizing the neck during all movements.
If you are walking, running, jumping, doing barre classes, bending over, cleaning, any dynamic motion, the SCM is working.
During a sudden motion with your body, or a fall, your SCM is working to stabilize the neck. As a protective reflex, the SCM works to protect you.
SCM and Neck Lordosis
Your cervical spine has an ideal range of curvature. The curvature of both the low back and the neck spine is called lordosis. The curvature can vary from person to person based on anatomical differences, but the range of curvature is between a 20-40 degrees. With some believing the curvature should be around 30-40 degrees. I believe that most people need more than 20 degrees, and therapy and symptom tracking can help to find the ideal range.
In my practice, I feel the curves of women’s necks and within seconds, know that they have a loss of cervical curvature. This may change their timeline of care, but they can heal and reestablish proper cervical curvature. Women seeking jaw pain relief will go to a TMJ dentists and do very expensive TMJ programs, but never have their necks checked.
I have seen many of these women whose pain was coming from their neck and some of these women have completely straight cervical curves. Left unaddressed these women will have degenerative changes to their spine, and issues with vagal tone (the vagus nerve).
When the SCM is tight and tense, it—with the scalene muscles—will pull the neck forward. Over time, this anterior pull on the neck will cause a loss of cervical curvature. Left unaddressed, degenerative changes will occur.
The SCM and Whole Body Posture
The neck and the jaw will influence posture down to your feet. Your neck and your hips can have connected postural concerns, but the neck can be the first place of concern, as it certainly has many powerful forces acting upon it. This includes looking down at the keyboard, looking down at your laptop, and your phone. The eyes are taking in stimulation, and at the same time, your brain is working through the SCMs to track, stabilize, protect, and move your head.
Let’s talk about how your feet and/or hips can affect the SCM. If your foot, hips, or torso rotates to one side, your SCM must work harder to return your head to the midline. A right-sided torso rotation will cause the right SCM to counter and contract. This counter motion to draw your head and eyes back starlight, will create an overactive SCM.
SCM Trigger Points
I have custom drawings of muscles and muscles with trigger points coming soon! These will be available to buy!
The SCM muscle trigger points refer pain broadly throughout the head. Trigger points hold spontaneous electrical activity, and as mentioned at the start of this article, people with chronic neck pain have heightened electrical activity in their SCM muscles.
The sternal head refers pain into the occiput (the back of the head) and up into the eyebrow.
The clavicular head refers pain to the forehead area above the eye, into the ear, behind the ear on the mastoid process.
Issues with the mastoid process cause proprioceptive issues and dizziness. The clavicular head often refers pain to the mastoid process, but as the SCM insertion (a tendon) is located on the mastoid process, it itself can be inflamed and cause issues. And the mastoid process being pulled on by a tight muscle belly will cause the issues with ear pain and dizziness.
So what Heals the SCM?
More on that in another post very soon!
Want to Know More?
Check out my books on health and wellness!
The Elemental Woman
A Conversation for the Modern Western Woman Inspired by the Healing Wisdom of the Ancient Eastern Sage
Food & Mood Journal
A tracking guide to connect the food you eat, the emotions you feel, and increase the feeling of deep self-love
Mindful Movement Journal
A tracking guide to connect the motions you make, the emotions you feel, and increase the feeling of deep self-love
Basic Ayurveda
The Elemental Woman Supplement Guide
About the author:
Since 2004, Tara Lee Clasen has been assisting women on their healing adventures. As a woman-focused physical medicine provider, also trained in Eastern medicine, she knows transformation is possible and knows that with reflection and self-love, your future is full of bright possibilities.
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Resources
The Concise Book of Trigger Points by Simeon Niel-Asher, 3rd edtion
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