WBR0586

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 45 year old woman with past medical history significant for resected breast cancer presents to the emergency department after suffering a tonic-clonic seizure lasting 3 minutes. She explains that she was walking her dog and then found herself on the ground with several people surrounding her, not knowing what had happened. The patient explains that she had been recovering well after her last chemotherapy cycle, and had no complaints except an annoying area of visual field disturbance she noticed recently. On physical exam, you notice the pattern of visual loss shown below. You order a brain MRI that shows a intracranial lesion with high suspicion for metastasis. Where is the most likely location of the lesion given the patient's symptoms? ]]
Answer A	AnswerA::Parietal lobe
Answer A Explanation	[[AnswerAExp::Parietal lobe lesions are usually associated with inferior homonymous quadrananopia due to the interruption of the dorsal optic radiations (Baum's loop). Parietal lobe lesions do not usually cause superior quadrantanopia except if large enough to cause a mass effect.]]
Answer B	AnswerB::Frontal lobe
Answer B Explanation	[[AnswerBExp::Frontal lobe lesions usually cause visual field defects by compression the optic tracts or the optic nerve causing unilateral anopia. Frontal lesions can also affect the frontal eye fields involved in eye movements, such as voluntary saccades and pursuit. Frontal lobe lesions do not usually cause quadrantanopia.]]
Answer C	AnswerC::Temporal lobe
Answer C Explanation	AnswerCExp::Temporal lobe lesions usually present with visual field disturbances similar to our patient. Superior quadrantanopia is seen in temporal lesions due to the interruption of the Meyer's loop
Answer D	AnswerD::Occipital lobe
Answer D Explanation	AnswerDExp::Occipital lobe lesions usually cause homonymous hemianopia, although cases of quadrantanopia are also encountered. However, superior quadrantanopia is classically seen in temporal lobe lesions.
Answer E	AnswerE::Cerebellum
Answer E Explanation	AnswerEExp::The cerebellum is not associated with visual field defects.
Right Answer	RightAnswer::C
Explanation	[[Explanation:: Superior homonymous quadrantanopia is characterized by loss of vision in the upper quadrant of the visual field. It usually occurs with contralateral temporal lesions due to the interruption of the left Meyer's loop. Although classically associated with the temporal lobe, it can also occur with certain lesions to the contralateral lateral geniculate nucleus (LGN) and certain localized lesions to the contralateral visual cortex. Superior quadrantanopia is commonly seen in patients with direct temporal lobe trauma, temporal lobe tumors commonly metastatic, or MCA infarcts. Educational objective: Superior quadrantanopia is characteristic of temporal lesions due to the interruption of the Meyer's loop. References: Jacobson DM. The localizing value of a quadrantanopia. Arch Neurol. 1997;54(4):401-4. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::Upper quadrantopia, WBRKeyword::Temporal lesions, WBRKeyword::Visual field defects
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::