WBR0328
| Author | [[PageAuthor::Serge Korjian M.D. (Reviewed by Alison Leibowitz) (Reviewed by Serge Korjian)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Anatomy |
| Sub Category | SubCategory::Head and Neck |
| Prompt | [[Prompt::A 32-year-old man presents to the physician's office with complaints of right shoulder pain radiating to the neck and upper back for the past 3 weeks. He reports that the pain started after getting hit on the neck during a recent basketball game. Physical exam reveals normal passive motion but limited sustained abduction of the shoulder. Which other finding is most likely to be present 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 responsible for opening 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::The CN XII, hypoglossal nerve, innervates the tongue. |
| Answer D | AnswerD::Inability to preform arm abduction |
| Answer D Explanation | AnswerDExp::Arm abduction relies on the deltoid muscles and 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 relies on the CN IX or the glossopharyngeal nerve. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::The patient in this scenario most likely has an injury to his sternocleidomastoid muscle (SCM), which is responsible for the lateral flexion of the neck and the rotation of the head. The SCM is innervated by CN XI, or the spinal accessory nerve, which also innervates the trapezius, the main muscle responsible for shoulder shrugging. 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. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::trapezius, WBRKeyword::sternocleidomastoid, WBRKeyword::SCM, WBRKeyword::innervate, WBRKeyword::innervation, WBRKeyword::cranial nerves, WBRKeyword::accessory nerves |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |