WBR0489
| Author | PageAuthor::William J Gibson |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Anatomy |
| Sub Category | SubCategory::Musculoskeletal/Rheumatology, SubCategory::General Principles |
| Prompt | [[Prompt::An eight-year-old male is brought to the emergency room after falling from a tree. He was able to break his fall by grabbing onto a branch with his right hand during his descent. He reports 8/10 pain of his right arm and is unable to extend his wrist. His right hand in clenched, in a “claw hand” configuration pictured below. On physical exam, the child has significant swelling on the left side of his body and scratches from the fall, but no evidence of skeletal fractures. Which of the following nerves is most likely damaged in this patient?
 Insert picture here]] |
| Answer A | AnswerA::Median Nerve |
| Answer A Explanation | [[AnswerAExp::Incorrect: The median nerve is not typically damaged in Krumpke’s palsy. However, patients with Krumpke palsy will exhibit weakness of the thenar eminence innervated by the median nerve. These muscles are innervated by the nerves passing through the median nerve from the C8-T1 nerve roots.]] |
| Answer B | AnswerB::Radial Nerve |
| Answer B Explanation | [[AnswerBExp::Incorrect: The radial nerve is not injured in Krumpke’s palsy. The radial nerve can be injured in Erb’s palsy, a condition in which the superior trunk of the brachial plexus is injured. Erb’s palsy causes a “waiter’s tip” appearance of the arm and hand.]] |
| Answer C | AnswerC::Ulnar Nerve |
| Answer C Explanation | [[AnswerCExp::Incorrect: While the injured C8-T1 nerve roots give rise to the ulnar nerve, the ulnar nerve itself is not damaged in Krumpke’s palsy. A lesion of the ulnar nerve can be caused by a fracture of the medial epicondyle of the humerus, giving rise to the “ulnar claw”. In this condition, the fourth and fifth digits are flexed when attempting to open the hand.]] |
| Answer D | AnswerD::C5-C6 |
| Answer D Explanation | AnswerDExp::'''Incorrect:''' These are the nerve roots injured in Erb’s palsy. |
| Answer E | AnswerE::C8-T1 |
| Answer E Explanation | AnswerEExp::'''Correct:''' Krumpke’s palsy is caused by injury of the C8-T1 nerve roots. |
| Right Answer | RightAnswer::E |
| Explanation | [[Explanation::The patient in this vignette has Krumpke’s palsy, a condition caused by damage to the inferior trunk of the brachial plexus (nerve roots C8-T1). Krumpke’s palsy is often caused by forceful, excessive abduction of the arm. This can occur during an attempt to catch oneself during a fall, or when an infant’s arm is abducted during a difficult vaginal birth. The patient will often have the classic “Krumpke’s (total) claw” hand appearance due to loss of lumbrical function. The ulnar nerve supplies the third and fourth lumbricals (the most ulnar two digits) as well as the flexors of the wrist. The C8-T1 fibers of the median nerve supply the first and second lumbricals. Krumpke’s palsy has a worse prognosis than Erb’s palsy.
 Educational Objective: The inferior trunk of the brachial plexus is injured in Krumpke’s palsy. References: First Aid 2012 page 408, 410 |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Krumpke, WBRKeyword::Palsy, WBRKeyword::Arm, WBRKeyword::Nerve, WBRKeyword::Paralysis, WBRKeyword::Muscle, WBRKeyword::Hand |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |