WBR0328

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Anatomy
Sub Category	SubCategory::Head and Neck
Prompt	Prompt::A 42-year-old male patient presents to the physician's office with complaints of an inability to laterally flex his neck or rotate his head. Upon physical examination, which other finding is most likely demonstrated in this patient?
Answer A	AnswerA::Inability to elevate his shoulder
Answer A Explanation	AnswerAExp::Cranial nerve (CN) XI or the spinal accessory nerve innervates the trapezius, which is the muscle responsible for elevation or shrugging of the shoulder.
Answer B	AnswerB::Inability to open his jaw
Answer B Explanation	AnswerBExp::The lateral pterygoid is the main muscle the opens the jaw. All jaw muscles are innervated by the trigeminal nerve - the mandibular branch (CN V3).
Answer C	AnswerC::Inability to protrude his tongue
Answer C Explanation	AnswerCExp::CN XII or hypoglossal nerve is the nerve responsible for tongue motor function.
Answer D	AnswerD::Inability to elevate his arm
Answer D Explanation	AnswerDExp::Elevation of arm is achieved by the deltoid muscles and to some extent by the supraspinatus muscle. The deltoid muscle is innervated by the axillary (C5-C6) nerve. The supraspinatus muscle is innervated by the suprascapular (C5-C6) nerve.
Answer E	AnswerE::Inability to swallow
Answer E Explanation	AnswerEExp::Swallowing is mainly achieved by CN IX or the glossopharyngeal nerve.
Right Answer	RightAnswer::A
Explanation	[[Explanation::The patient is presenting with signs consistent with injury to the sternocleidomastoid muscle, which is responsible for the lateral flexion of the neck and the rotation of the head. The sternocleidomastoid muscle originates in the anterior and superior manubrium and superior medial third of the clavicle and inserts in the lateral aspect of the mastoid process and anterior half of the superior nuchal line. It attaches the sternum, the clavicle, and the mastoid and occipital bones. The sternocleidomastoid is innervated by CN XI, or the spinal accessory nerve, which also innervates the trapezius, the main muscle responsible for the elevation of the shoulder. Educational Objective: Sternocleidomastoid laterally flexes the neck and rotates the head. It is innervated by CN XI. The trapezius muscle, which elevates the shoulder, is also innervated by CN XI. References: First Aid 2014 page 67]]
Approved	Approved::No
Keyword	WBRKeyword::trapezius, WBRKeyword::sternocleidomastoid, WBRKeyword::shoulder, WBRKeyword::elevate, WBRKeyword::elevation, WBRKeyword::physical, WBRKeyword::examination, WBRKeyword::exam, WBRKeyword::muscle, WBRKeyword::innervate, WBRKeyword::innervation, WBRKeyword::cranial, WBRKeyword::nerve, WBRKeyword::11, WBRKeyword::XI, WBRKeyword::spinal, WBRKeyword::accessory, WBRKeyword::nerve, WBRKeyword::shrug, WBRKeyword::shrugging, WBRKeyword::lateral, WBRKeyword::flex, WBRKeyword::flexion, WBRKeyword::rotate, WBRKeyword::rotation, WBRKeyword::head
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::