A 34-year-old woman comes to the physician complaining of double vision. She first experienced difficulty focusing her eyes while at work yesterday. Upon waking up this morning, her symptoms had progressed to frank diplopia. Her past medical history is insignificant. A complete physical examination is performed, including a full neurologic assessment. Shining light into her right eye causes constriction of her right pupil, but not the left pupil. Shining light into her left eye causes constriction of only her right pupil. Which of the following additional physical examination findings is likely to be found in this patient?

Question

A 34-year-old woman comes to the physician complaining of double vision.  She first experienced difficulty focusing her eyes while at work yesterday.  Upon waking up this morning, her symptoms had progressed to frank diplopia.  Her past medical history is insignificant.  A complete physical examination is performed, including a full neurologic assessment.  Shining light into her right eye causes constriction of her right pupil, but not the left pupil.  Shining light into her left eye causes constriction of only her right pupil.  Which of the following additional physical examination findings is likely to be found in this patient?

Quizplus · Accepted Answer

11ec160b_35d5_86a6_9249_87b4a805a57a_MD0001_00 The pupillary light reflex is assessed by shining light in an eye and observing the response in that eye (direct) as well as the opposite eye (consensual). The optic nerve (CN II) is responsible for the afferent limb of this reflex; the oculomotor nerve (CN III) is responsible for the efferent limb. In this patient, the right CN II and right CN III are functional as there was a direct response seen when light was shined into the right eye. In addition, the left CN II is also functional as a consensual response occurred when light was shined into the left eye. However, constriction of the left pupil was not seen in either circumstance. Thus, this patient's lesion most likely involves her left CN III. The symptoms of CN III palsy relate to the function of CN III: CN III palsy can result from lesions anywhere along the nerve's path from the oculomotor nucleus in the midbrain to the extraocular muscles within the orbit. The most dreaded cause of isolated acute third nerve palsy is an actively enlarging intracranial aneurysm (at risk of imminent rupture). (Choice A) Absence of the corneal reflex can result from lesions involving CN V₁ (afferent limb) or CN VII (efferent limb). (Choice C) A lesion involving the left CN VII would result in inability to close the left eye. (Choice D) Inward deviation of the left eye would result from a CN VI lesion and the resultant unopposed action of CN III. (Choice E) The left CN II is functional as it was able to produce a consensual response in the right eye. Educational objective: The pupillary light reflex is assessed by shining light in an eye and observing the response in that eye (direct) and the opposite eye (consensual). The optic nerve (CN II) is responsible for the afferent limb of the pupillary reflex, and the oculomotor nerve (CN III) is responsible for the efferent limb.

A 34-Year-Old Woman Comes to the Physician Complaining of Double