Many times when dealing with pain, where we feel the pain is not actually the source of the pain. It can be referred pain from a neighboring muscle. Think you have pain from the sternocleidomastoid muscle? Look deeper; the posterior belly of the digastric muscle refers pain to the upper part of the sternocleidomastoid muscle, the throat and under the chin.
The digastric originates from the mastoid process, deep to the infamous sternocleidomastoid, the splenius capitis and the longissimus capitis. It consists of two fleshy bellies properly called the posterior belly and anterior belly, which are united by an intermediate rounded tendon. This tendon passes through a tendinous pulley attached to the hyoid bone. The two bellies of the digastric muscle have different embryological origins, and are supplied by different cranial nerves. The action of the digastric muscle is to depress the mandible when the hyoid bone is fixed and to retract and elevate the hyoid bone when the mandible is fixed. If you were experiencing pain at the mastoid process, your logical conclusion would be the sternocleidomastoid muscle. Think again: it could be coming from the posterior belly of the digastric muscle. The upper portions of the sternocleidomastoid muscle will be tender to the touch a result of trigger points from the posterior belly of the digastric muscle. The digastric develops these trigger points due to the association of other mastication muscles resulting from issues such as craniomandibular syndrome, mouth breathing due to allergies and sinus issue. The digastric can also cause a deep ear pain described as being in front of or below the ear that is not caused by an ear infection. Other then pain, another indicator the digastric maybe your culprit is difficulty swallowing.
Below is a blurb and image regarding the trigger points of the digastric. “Start with your fingers in the soft part of the flesh underneath the jaw and in front of its corner, just anterior to the upper part of the sternocleidomastoid. From here run your fingers along the front border of the SCM up toward your earlobe, feeling for the very tender spots. Sustained pressure may reproduce the referred pain symptoms. (1)” To help release the posterior belly of the digastric you can use two fingers to press and massage just below the corner of the mandible (where the x is in the above drawing). Press gently inward toward the back of your throat. If you feel your tonsils, stay above them.
Check back on Friday for some therapy ball, self massage, and trigger point therapy tips for your digastric!