WBR0583

Author	[[PageAuthor::Serge Korjian M.D. (Reviewed by Serge Korjian)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Anatomy, MainCategory::Pathophysiology, MainCategory::Pharmacology
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 82-year-old man with history of stroke maintained on ASA and clopidogrel presents with 2 hours of acute left-sided vision loss, confusion, and new onset occipital headache. On physical exam, the patient has no focal neurologic deficits except for decreased left visual field. The patient describes having a crescent-like obstruction that spares his central vision but obscures a significant part of his left visual field. Which of the following arteries is most likely occluded in this patient? ]]
Answer A	AnswerA::A
Answer A Explanation	AnswerAExp::This represents the anterior cerebral artery (ACA). The ACA supplies the medial portions of the frontal lobes and superiomedial parietal lobes. ACA strokes usually present with contralateral lower extremity sensory-motor deficit.
Answer B	AnswerB::B
Answer B Explanation	AnswerBExp::This refers to the right posterior cerebral artery (PCA) whose occlusion can explain the symptoms in our patient. PCA strokes usually cause contralateral homonymous hemianopia with macular sparing.
Answer C	AnswerC::C
Answer C Explanation	AnswerCExp::This refers to the middle cerebral artery (MCA). Occlusion of the MCA in the dominant hemisphere leads to contralateral facial and upper extremity sensory-motor deficits. Visual field defects are rare in MCA strokes.
Answer D	AnswerD::D
Answer D Explanation	[[AnswerDExp::This refers to the right posterior inferior cerebellar artery (PICA). PICA lesions present with lateral medullary syndrome characterized by crossed sensory deficits, vertigo, ataxia, ipsilateral Horner's syndrome, and nucleus ambiguus symptoms including dysphagia, hoarsness, and loss of gag reflex.]]
Answer E	AnswerE::E
Answer E Explanation	AnswerEExp::This refers to the left posterior cerebral artery (PCA) whose occlusion would cause a similar syndrome seen in our patient but localized to the right. PCA strokes usually cause contralateral homonymous hemianopia with macular sparing.
Right Answer	RightAnswer::B
Explanation	[[Explanation:: The occipital cortex, particularly the visual cortex is supplied by the posterior cerebral artery (PCA). Occlusion of the PCA usually presents with acute visual field loss contralateral to the side of the lesion. Classically, visual field loss is homonymous hemianopia with macular sparing. The macula is an oval-shaped spot near the center of the retina of the human eye. It is responsible for a significant part of the central vision. Macular sparing is hypothesized to be due to a collateral vascular supply to the macular region in the occipital cortex or due to the fact that the macular representation is a very large part of the visual cortex. Educational Objective: PCA strokes classically lead to acute contralateral homonymous hemianopia with macular sparing. References: Arboix A, Arbe G, García-Eroles L, Oliveres M, Parra O, Massons J. Infarctions in the vascular territory of the posterior cerebral artery: clinical features in 232 patients. BMC Res Notes. Sep 7 2011;4:329]]
Approved	Approved::Yes
Keyword	WBRKeyword::PCA, WBRKeyword::Stroke, WBRKeyword::Posterior cerebral artery, WBRKeyword::Homonymous hemianopia, WBRKeyword::Macular sparing, WBRKeyword::Visual field defects
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