Anatomy and supply
The temporal muscle, also know as the temporalis, is a flat, fan-shaped muscle of mastication on the lateral side of the skull. Due to its size it can be palpated without difficulty, especially when the patient opens and closes his mouth alternately. It arises from the temporal fossa, a large depression on the side of the skull, and the temporal fascia which completely covers the surface of the muscle. From there, the muscle descends through the gap between the zygomatic arch and the skull, forms a thick tendon and inserts at the coronoid process of mandible. The temporalis is innervated by the deep temporal nerves branching off from the mandibular nerve.
The temporalis is the most powerful muscle of the temporomandibular joint. Functionally, the muscle can be divided into two parts: The anterior part runs almost vertically and moves the mandible forward (protrusion). In contrast the fibers of the posterior part course almost horizontally and pull the mandible backwards (retrusion). The activation of both muscles moves the mandible dorsocranially leading to a strong jaw closure (elevation).
Tension of the temporal muscle can induce pain in the temporal area. Common causes include misalignments of the teeth and jaws, trauma and a prolonged immobilisation (e.g. after a mandibular fracture). Teeth grinding (bruxism) or a dental intervention during which the person's mouth had to be open for a long period of time can also trigger muscle tension. Clinically, it is important to rule out an inflammation of the superficial temporal artery, which runs in front of the ear along the zygomatic arch to the temporal area. Vasculitides, such as the giant cell arteritis, frequently involve the superficial temporal artery and cause swelling and massive pain in the temporal area. The diagnosis can be confirmed by a temporal artery biopsy.