In attempting to introduce a catheter into the right internal jugular vein, a resident inadveently damages the cervical sympathetic trunk in a patient. Which of the following findings is MOST likely to be seen in this patient as a result of the injury?

The right sympathetic trunk lies posterior to the right internal jugular vein, and may be injured in this procedure. Preganglionic sympathetic nerve fibers will be damaged. These nerve fibers synapse in the superior cervical ganglion on postganglionic sympathetic neurons that innervate structures in the head. The dilator pupillae muscle (smooth muscle of the iris that dilates the pupil) is sympathetically innervated; paralysis of this muscle due to interruption of its innervation results in constriction of the pupil (miosis). Good to know: Dilation of the pupil would result from paralysis of the sphincter pupillae muscle (smooth muscle of the iris that constricts the pupil). This muscle is parasympathetically innervated and would not be affected by this injury. An inability to abduct the eye would result from paralysis of the lateral rectus muscle, an extraocular muscle that is innervated by the abducens nerve. It would not be affected by this injury. An inability to close the eye (choice D) would result from paralysis of the orbicularis oculi muscle, a skeletal muscle of the face. This muscle is innervated by the facial nerve and would not be affected by this injury. Ref: LeBlond R.F., DeGowin R.L., Brown D.D. (2009). Chapter 14. The Neurologic Examination. In R.F. LeBlond, R.L. DeGowin, D.D. Brown (Eds), DeGowin's Diagnostic Examination, 9e.