An 25-year-old man is brought to the emergency department 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 severe pain in his right arm and is unable to extend his right wrist (shown below). On physical examination, the patient has several scratches from the fall but no evidence of skeletal fractures. Which of the following nerves is most likely injured in this patient?
4.C5-C6 nerve roots
Klumpke palsy is caused by damage to the inferior trunk of the brachial plexus (nerve roots C8-T1). Klumpke 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 vaginal birth. Individuals will often present with a characteristic Klumpke (total) “claw hand” appearance due to loss of lumbrical function, as displayed in the vignette. 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.