Digastric

The Digastric is an anterior muscle of the neck.

Anatomical Attachments:

• Origin: The Posterior belly attaches from the mastoid process of the temporal bone; the Anterior belly attaches to the fossa of the lower mandible.
• Insertion: Attaches by an intermediate tendon which becomes a fibrous loop at the hyoid bone.

Action: Elevates and stabilizes the hyoid bone and raises the base of the tongue.

Synergist: Lateral Pterygoid, Stylohyoid, Suprahyoid, and Infrahyoid  

Antagonist: Masseter, Temporalis, Medial Pterygoid, and Superior division of lateral Pterygoid.

Nerve Supply: The Posterior belly – Facial Nerve (Cranial VII); the Anterior belly – Trigeminal Nerve (Cranial V).

Vascular supply: The Posterior belly - Occipital and posterior auricular arteries; the Anterior belly - Branches of the submental artery.

• Primary: Each belly has its separate referral. The posterior belly radiates from the SCM or the anterior throat to beneath the chin. Travell and Simons qualify that the propensity of a trigger to become active in the anterior belly is less frequent, but when this occurs, it refers pain from the digastric to the four mandibular incisor teeth and their alveolar ridge.
• Satellite or associated triggers: Masseter, Sternocleidomastoid, and Temporalis.

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Trigger Point Signs and Symptoms: In addition to referral patterns, there maybe difficulty in swallowing with exquisite tenderness experienced with palpation. While ipsilateral visual blurring is usually associated with the SCM, this may occur occasionally with digastric involvement.

Trigger Point Activating and Perpetuating Factors: Clinching the teeth, breathing from the mouth, nasal disorders, Trigger Points from the surrounding muscles, and acceleration/deceleration injuries.

Differential Diagnosis: Eagle syndrome, Periapical infection, Polymyalgia rheumatica, Fibromyalgia, Carotid artery obstruction, Coronary involvement, Spasmodic torticollis (Wryneck syndrome), (Segmental, Subluxation, Somatic dysfunction) C2 radiculopathy, Broken tooth syndrome, disease of the lower incisors, Lymphedema, Systemic infections or inflammation, Nutritional inadequacy, Metabolic imbalance, Toxicity, Side effects of medication.

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