A 62-year-old man comes to the office reporting double vision. He first noticed mild difficulty focusing his eyes about 3 weeks ago, and his symptoms have progressively worsened. The patient's other medical problems include metastatic prostate cancer. On neurologic examination, he is unable to adduct his left eye, and stimulation of the left cornea does not elicit a corneal reflex. A lesion involving which of the following anatomical structures is most likely responsible for this patient's symptoms?

Question

A 62-year-old man comes to the office reporting double vision.  He first noticed mild difficulty focusing his eyes about 3 weeks ago, and his symptoms have progressively worsened.  The patient's other medical problems include metastatic prostate cancer.  On neurologic examination, he is unable to adduct his left eye, and stimulation of the left cornea does not elicit a corneal reflex.  A lesion involving which of the following anatomical structures is most likely responsible for this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_35a5_7594_9249_a51a44b859b7_MD0001_00 This patient has an absence of the blink reflex on stimulation of the left cornea, indicating a lesion in the afferent limb of the reflex. In combination with a deficit of globe adduction, this suggests a lesion at the superior orbital fissure. The sensory limb of the corneal reflex is mediated by the nasociliary branch of the first division of the trigeminal nerve (CN V₁), which enters the orbit through the superior orbital fissure. The motor component of the corneal reflex is carried primarily by the temporal branch of the facial nerve (CN VII) and causes a bilateral eye blink. Globe adduction is mediated by the medial rectus muscle, which is innervated by the oculomotor nerve (CN III). The oculomotor nerve originates in the oculomotor nucleus of the midbrain, emerges from the anterior midbrain, and enters the orbit through the superior orbital fissure. Most patients with lesions at the superior orbital fissure present with multiple deficits that may include ophthalmoplegia (oculomotor, trochlear, and abducens nerves); ptosis (levator palpebrae innervated by the oculomotor nerve); a fixed, dilated pupil (sympathetics of oculomotor nerve); and lacrimal hyposecretion and forehead numbness (V1). (Choice A) The foramen lacerum is occluded by cartilage. The internal carotid artery courses just superior to the foramen lacerum in the lacerum portion of the carotid canal. (Choice B) The mandibular branch of the trigeminal nerve (CN V₃) passes through the foramen ovale. (Choice C) The foramen rotundum transmits the maxillary division of the trigeminal nerve (CN V₂) from within the skull to the pterygopalatine fossa. From there, it courses through the inferior orbital fissure to appear on the face at the infraorbital foramen as the infraorbital nerve. (Choice D) The maxillary division of the trigeminal nerve (CN V₂), the infraorbital vessels, and branches from the sphenopalatine ganglion pass through the inferior orbital fissure but do not enter the orbit. (Choice E) The optic canal is medial to the superior orbital fissure and transmits the optic nerve (CN II) and ophthalmic artery. Educational objective: The oculomotor nerve (CN III), ophthalmic nerve (CN V₁) branches, trochlear nerve (CN IV), and abducens nerve (CN VI) enter the orbit via the superior orbital fissure.

A 62-Year-Old Man Comes to the Office Reporting Double Vision