A 30-year-old woman comes to the emergency department after a seizure. The patient reports pain on the left side of her face and is unable to fully open or close her mouth. She is drooling. On examination, the jaw deviates to the right and the left mandibular condyle is very prominent with a palpable depression posterior to it. The patient is diagnosed with an anterior dislocation of the left temporomandibular joint. The jaw is most likely maintained in a dislocated position due to continued spasm of which of the following muscles?

Question

A 30-year-old woman comes to the emergency department after a seizure.  The patient reports pain on the left side of her face and is unable to fully open or close her mouth.  She is drooling.  On examination, the jaw deviates to the right and the left mandibular condyle is very prominent with a palpable depression posterior to it.  The patient is diagnosed with an anterior dislocation of the left temporomandibular joint.  The jaw is most likely maintained in a dislocated position due to continued spasm of which of the following muscles?

Quizplus · Accepted Answer

11ec160b_356f_e73b_9249_3bed60696b22_MD0001_00 This patient has an anterior dislocation of the temporomandibular joint (TMJ), the synovial joint that opens and closes the jaw. The joint is formed by the mandibular condyle that sits in the glenoid fossa of the squamous portion of the temporal bone. TMJ opening involves a complex movement that has both hinge and sliding components: The initial movement is rotational (ie, hinge) and driven by the lateral pterygoid muscles, which are the only muscles of mastication that aid in depressing the mandible (ie, opening the jaw). As the jaw opens, the ligaments become taut, stopping further rotation. Further action by the lateral pterygoids results in translational movement (ie, condyle slides anteriorly) that opens the jaw fully. TMJ dislocation occurs when translational movement is exaggerated due to extreme jaw opening (eg, yawning, orotracheal intubation, seizure) that causes displacement of the condyle anteriorly out of the glenoid fossa. Stretching of the ligaments causes significant pain and spasm of the muscles of mastication. This muscle spasm (specifically of the lateral pterygoids that aid jaw opening) prevents spontaneous resolution of the dislocation; manual reduction is usually necessary. (Choice A) The buccinator muscle underlies the cheek. It holds the cheek close to the teeth to control food boluses during chewing but is not involved in movement of the jaw. (Choice B) The genioglossus muscles form the body of the tongue. Although they originate on the tubercle of the mandible (and insert into the hyoid bone and the bottom of the tongue), they are responsible for tongue protrusion rather than mandibular movement. (Choice D) The sternocleidomastoid muscles originate at the sternum and the clavicle and insert on the mastoid tip. They rotate the head (when acting independently) or flex the neck (when acting in concert). (Choice E) The superior pharyngeal constrictor forms portions of the posterior and lateral oropharyngeal walls. Muscle contraction propels food and liquid inferiorly into the esophagus during swallowing. (Choice F) The zygomaticus major originates from the zygomatic bone and inserts onto the angle of the mouth. Contraction pulls the angle of the mouth laterally and superiorly during a smile. Educational objective: The lateral pterygoid muscles are the only muscles of mastication that aid in depressing the mandible (ie, opening the jaw). Spasm of the lateral pterygoids prevents spontaneous reduction of an anterior dislocation of the temporomandibular joint. __________ References: Temporomandibular joint dislocation. (http://www.ncbi.nlm.nih.gov/pubmed/26668447) The emerging role of botulinum toxin in the treatment of temporomandibular disorders (http://www.ncbi.nlm.nih.gov/pubmed/17448205)

A 30-Year-Old Woman Comes to the Emergency Department After a Seizure