WBR0584

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathophysiology
Sub Category	SubCategory::Head and Neck, SubCategory::Neurology
Prompt	[[Prompt::A 32 year old woman presents to the gynecology clinic for 3 months of absent menstruation. The patient has been trying to get pregnant for the past year but has been unsuccessful. She reports decreased libido and episodes of bilateral milky breast discharge. Which of the following visual field patterns is most likely present in this patient?]]
Answer A	[[AnswerA::]]
Answer A Explanation	AnswerAExp::Homonymous hemianopia involves loss of vision on one side. It usually occurs due to a lesion to the optic tracts or a PCA stroke although the latter usually has associated macular sparing. This lesion is not seen with prolactinomas.
Answer B	[[AnswerB::]]
Answer B Explanation	[[AnswerBExp::Right upper quadrantanopia is characterized by loss of vision in the right upper quadrant of the visual field. It usually occurs with left temporal lesions due to the interruption of the left Meyer's loop. Prolactinomas do not affect the temporal lobe.]]
Answer C	[[AnswerC::]]
Answer C Explanation	AnswerCExp::Left nasal hemianopia usually occurs with lesions of the internal carotid artery (internal carotid thrombosis) that occur lateral to the optic chiasm. This presentation is not typical of prolactinomas.
Answer D	[[AnswerD::]]
Answer D Explanation	AnswerDExp::This lesion portrays bitemporal hemianopia seen in large prolactinomas that abut the optic chiasm.
Answer E	[[AnswerE::]]
Answer E Explanation	[[AnswerEExp::Right lower quadrantanopia is characterized by loss of vision in the right lower quadrant of the visual field. It usually occurs with left parietal lesions due to the interruption of the left dorsal optic radiations. Prolactinomas do not usually affect the parietal lobe.]]
Right Answer	RightAnswer::D
Explanation	[[Explanation:: The patient has a typical presentation of hyperprolactinemia which is usually characterized by amenorrhea, infertility, decreased libido, bilateral milky breast discharge, and osteoporosis if untreated. The most common cause of hyperprolactinemia is a pituitary tumor known as prolactinoma. As the prolactinoma enlarges it impinges on the optic chiasm leading to bitemporal hemianopia manifesting as loss of peripheral vision with patients complaining of bumping into objects and having difficulty with driving. Educational objective: Prolactinomas are prolactin secreting tumors of the pituitary that can enlarge to compress the underlying optic chiasm and cause bitemporal hemianopia. References: Jay WM. Visual field defects. Am Fam Physician. 1981;24(2):138-42. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::Bitemporal hemianopia, WBRKeyword::Prolactinoma, WBRKeyword::Visual field defects
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::