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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{Rim}} {{Alison}}
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Anatomy
|MainCategory=Anatomy
Line 21: Line 21:
|SubCategory=Head and Neck
|SubCategory=Head and Neck
|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?
|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?
|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.
|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.


|EducationalObjectives= 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.
|EducationalObjectives= 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
|References= First Aid 2014 page 472
|AnswerA=Inability to elevate his shoulder
|AnswerA=Inability to elevate his shoulder
|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.
|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.
|AnswerB=Inability to open his jaw
|AnswerB=Inability to open his jaw
|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).
|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).
|AnswerC=Inability to protrude his tongue
|AnswerC=Inability to protrude his tongue
|AnswerCExp=CN XII or hypoglossal nerve is the nerve responsible for tongue motor function.
|AnswerCExp=The CN XII, hypoglossal nerve, innervates the tongue.
|AnswerD=Inability to elevate his arm
|AnswerD=Inability to preform arm abduction
|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.
|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.
|AnswerE=Inability to swallow
|AnswerE=Inability to swallow
|AnswerEExp=Swallowing is mainly achieved by CN IX or the glossopharyngeal nerve.
|AnswerEExp=Swallowing relies on the CN IX or the glossopharyngeal nerve.
|RightAnswer=A
|RightAnswer=A
|WBRKeyword=trapezius, sternocleidomastoid, shoulder, elevate, elevation, physical, examination, exam, muscle, innervate, innervation, cranial, nerve, 11, XI, spinal, accessory, nerve, shrug, shrugging, lateral, flex, flexion, rotate, rotation, head
|WBRKeyword=trapezius, sternocleidomastoid, SCM, innervate, innervation, cranial nerves, accessory nerves,
|Approved=No
|Approved=Yes
}}
}}

Revision as of 14:31, 14 July 2014
Author [[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz)]]
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 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.
References: First Aid 2014 page 472]]

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::
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