An unconscious 48-year-old woman is admitted to the hospital. CT scan reveals a tumor in her brain. When she regains consciousness, her right eye is directed laterally and downward, with complete ptosis of her upper eyelid, and her pupil is dilated. Which of the following structures was most likely affected by the tumor to result in these symptoms?
Correct Answer: Oculomotor nerve
Description: An injury to the oculomotor nerve would cause the eye to point downward and laterally due to the unopposed contractions of the trochlear and abducens nerves. The oculomotor nerve also provides innervation to the levator palpebrae superioris; thus, any injury would cause complete ptosis or drooping of the eyelid. The constriction of the pupil is provided by parasympathetic nerves via the oculomotor nerve. The optic nerve is responsible only for the sensory aspect of light via the retina in the eye. The facial nerve innervates the facial muscles, including the orbicularis oculi, which supplies the blink reflex. The ciliary ganglion could be damaged in this patient, but the loss of parasympathetic supply would not adequately explain the ptosis of the eyelid. The superior cervical ganglion provides sympathetic innervation to the head and neck, but no loss of sympathetics is evident in this patient.
Category:
Anatomy
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