WBR0495

Author	PageAuthor::William J Gibson
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Anatomy
Sub Category	SubCategory::Musculoskeletal/Rheumatology, SubCategory::Oncology, SubCategory::General Principles
Prompt	[[Prompt::A 52 year old woman presents to her primary care physician after noticing a firm lump in her breast. She undergoes fine needle aspiration of the mass, which reveals a grade 3 invasive ductal carcinoma with overexpression of the HER2/Neu oncogene. The woman undergoes surgical resection of the mass and the axillary lymph nodes. She is treated with adjuvant Trastuzumab and undergoes breast reconstruction. Two weeks after her surgery, she notices that her scapula protrudes when she lifts her arm. Which of the following nerves give rise to the affected nerve in this patient?]]
Answer A	AnswerA::C5-C6
Answer A Explanation	AnswerAExp::'''Incorrect:''' The C5-C6 nerve roots give rise to the axillary nerve and the posterior cord of the brachial plexus. These nerves are damaged in Erb’s palsy.
Answer B	AnswerB::C5-C7
Answer B Explanation	AnswerBExp::'''Correct:''' The C5-C7 nerve roots give rise to the long thoracic nerve. The long thoracic nerve innervates the serratus anterior and
Answer C	AnswerC::C8-T1
Answer C Explanation	AnswerCExp::'''Incorrect:''' the C8-T1 nerve roots give rise to the inferior trunk of the brachial plexus. These nerves are injured in Krumpke’s palsy.
Answer D	AnswerD::Inferior trunk of the brachial plexus
Answer D Explanation	AnswerDExp::'''Incorrect:''' the inferior trunk of the brachial plexus is injured in Krumpke’s palsy.
Answer E	AnswerE::Posterior cord of the brachial plexus
Answer E Explanation	AnswerEExp::'''Incorrect:''' the posterior cord of the brachial plexus gives rise to the axillary and radial nerves.
Right Answer	RightAnswer::B
Explanation	[[Explanation::The patient in this vignette has suffered damage to the long thoracic nerve as a result of radical mastectomy. The long thoracic nerve arises from the C5-C7 nerve roots to innervate the serratus anterior muscle. The serratus anterior normally serves to abduct the arm beyond 90 degrees to the body. Lesion of this nerve can lead to “winging” of the scapula. Educational Objective: Lesion of the long thoracic nerve, derived from the C5-C7 nerve roots, leads to winging of the scapula. References: First Aid 2012 page 411 Educational Objective: References: ]]
Approved	Approved::Yes
Keyword	WBRKeyword::Breast, WBRKeyword::Nerve, WBRKeyword::Long thoracic nerve, WBRKeyword::Brachial, WBRKeyword::Brachial plexus, WBRKeyword::Arm, WBRKeyword::Paralysis, WBRKeyword::Serratus, WBRKeyword::Muscle
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