WBR0585: Difference between revisions

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|MainCategory=Pathophysiology
|MainCategory=Pathophysiology
|SubCategory=Head and Neck, Neurology
|SubCategory=Head and Neck, Neurology
|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?
|Prompt=A 60 year old man presents to the neurology clinic for 2 months of left sided throbbing headache. The man has no significant past medical history except for hypertension. He describes a constant retroorbital headache non-responsive to regular analgesic therapy. He did not make much of the headache until recently when he noticed changes in his visual field which prompted him to seek medical care. His neurologist orders a brain MRI that shows a large left internal carotid artery aneurysm at the origin of the ophthalmic artery. Which of the following visual field defects would you expect in this patient?
|Explanation=[[Image:Optic_tracts_with_explanation.jpg|900px]]
|Explanation=[[Image:Optic_tracts_with_explanation.jpg|900px]]




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.
Internal carotid artery aneurysms, specifically those arising at the origin of the ophthalmic artery and closest to the lateral border of the optic chiasm can cause ipsilateral nasal hemianopia. This is cause by the compression of the lateral part of the optic nerve as it becomes the optic tract.  




Educational objective: Prolactinomas are prolactin secreting tumors of the pituitary that can enlarge to compress the underlying optic chiasm and cause bitemporal hemianopia.
Educational objective: internal carotid artery aneurysms can compress the lateral part of the optic nerve causing ipsilateral nasal hemianopia.




References:
References:
Cox TA, Corbett JJ, Thompson HS, Kassell NF. Unilateral nasal hemianopia as a sign of intracranial optic nerve compression. Am J Ophthalmol. 1981;92(2):230-2.
Jay WM. Visual field defects. Am Fam Physician. 1981;24(2):138-42.
Jay WM. Visual field defects. Am Fam Physician. 1981;24(2):138-42.
|AnswerA=[[Image:Visual1.gif]]
|AnswerA=[[Image:Visual1.gif]]
|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.
|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 in patients with carotid artery aneurysms.
|AnswerB=[[Image:Visual2.gif]]
|AnswerB=[[Image:Visual2.gif]]
|AnswerBExp=Right upper quadrantopia 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.
|AnswerBExp=Right upper quadrantopia 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. This pattern is unusual with carotid artery aneurysms.
|AnswerC=[[Image:Visual3.gif]]
|AnswerC=[[Image:Visual3.gif]]
|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.
|AnswerCExp=Left nasal hemianopia usually occurs with lesions of the internal carotid artery (internal carotid thrombosis or anyrysms) at the origin of the ophthalmic artery. The lesion is usually located laterally to the optic chiasm interrupting part of the optic nerve as it becomes the optic tract. Our patient would best fit this pattern of visual field loss.
|AnswerD=[[Image:Visual4.gif]]
|AnswerD=[[Image:Visual4.gif]]
|AnswerDExp=This lesion portrays bitemporal hemianopia seen in large prolactinomas that abut the optic chiasm.
|AnswerDExp=This lesion portrays bitemporal hemianopia usually seen in large prolactinomas that compress the optic chiasm. It is unusual in cases with internal carotid artery lesions.
|AnswerE=[[Image:Visual5.gif]]
|AnswerE=[[Image:Visual5.gif]]
|AnswerEExp=Right lower quadrantopia 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.
|AnswerEExp=Right lower quadrantopia 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.
|RightAnswer=D
|RightAnswer=C
|WBRKeyword=Bitemporal hemianopia, Prolactinoma, Visual field defects
|WBRKeyword=Nasal hemianopia, Carotid artery aneurysm, Visual field defects
|Approved=No
|Approved=No
}}
}}

Revision as of 03:00, 6 October 2013
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 60 year old man presents to the neurology clinic for 2 months of left sided throbbing headache. The man has no significant past medical history except for hypertension. He describes a constant retroorbital headache non-responsive to regular analgesic therapy. He did not make much of the headache until recently when he noticed changes in his visual field which prompted him to seek medical care. His neurologist orders a brain MRI that shows a large left internal carotid artery aneurysm at the origin of the ophthalmic artery. Which of the following visual field defects would you expect 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 in patients with carotid artery aneurysms.]]
Answer B [[AnswerB::]]
Answer B Explanation [[AnswerBExp::Right upper quadrantopia 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. This pattern is unusual with carotid artery aneurysms.]]
Answer C [[AnswerC::]]
Answer C Explanation [[AnswerCExp::Left nasal hemianopia usually occurs with lesions of the internal carotid artery (internal carotid thrombosis or anyrysms) at the origin of the ophthalmic artery. The lesion is usually located laterally to the optic chiasm interrupting part of the optic nerve as it becomes the optic tract. Our patient would best fit this pattern of visual field loss.]]
Answer D [[AnswerD::]]
Answer D Explanation AnswerDExp::This lesion portrays bitemporal hemianopia usually seen in large prolactinomas that compress the optic chiasm. It is unusual in cases with internal carotid artery lesions.
Answer E [[AnswerE::]]
Answer E Explanation AnswerEExp::Right lower quadrantopia 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.
Right Answer RightAnswer::C
Explanation [[Explanation::File:Optic tracts with explanation.jpg


Internal carotid artery aneurysms, specifically those arising at the origin of the ophthalmic artery and closest to the lateral border of the optic chiasm can cause ipsilateral nasal hemianopia. This is cause by the compression of the lateral part of the optic nerve as it becomes the optic tract.


Educational objective: internal carotid artery aneurysms can compress the lateral part of the optic nerve causing ipsilateral nasal hemianopia.


References: Cox TA, Corbett JJ, Thompson HS, Kassell NF. Unilateral nasal hemianopia as a sign of intracranial optic nerve compression. Am J Ophthalmol. 1981;92(2):230-2.

Jay WM. Visual field defects. Am Fam Physician. 1981;24(2):138-42.
Educational Objective:
References: ]]

Approved Approved::No
Keyword WBRKeyword::Nasal hemianopia, WBRKeyword::Carotid artery aneurysm, WBRKeyword::Visual field defects
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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