{"id":7931,"date":"2025-10-27T00:01:49","date_gmt":"2025-10-27T08:01:49","guid":{"rendered":"https:\/\/www.osmosis.org\/blog\/?p=7931"},"modified":"2025-10-01T16:34:22","modified_gmt":"2025-10-02T00:34:22","slug":"usmle-step-1-question-of-the-day-vascular-ischemia","status":"publish","type":"post","link":"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-vascular-ischemia","title":{"rendered":"USMLE\u00ae Step 1 Question of the Day:\u00a0Vascular ischemia"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_80 ez-toc-wrap-center counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">In This Article<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-vascular-ischemia\/#The_correct_answer_to_todays_USMLE%C2%AE_Step_1_Question_is%E2%80%A6\" >The correct answer to today\u2019s USMLE\u00ae Step 1 Question is\u2026<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-vascular-ischemia\/#Incorrect_Answer_Explanations\" >Incorrect Answer Explanations<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-vascular-ischemia\/#Main_Explanation\" >Main Explanation<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-vascular-ischemia\/#Major_Takeaway\" >Major Takeaway&nbsp;<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-vascular-ischemia\/#Want_to_learn_more_about_this_topic\" >Want to learn more about this topic?<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-vascular-ischemia\/#References\" >References<\/a><\/li><\/ul><\/nav><\/div>\n\n<p class=\"wp-block-paragraph\"><strong><em>Today\u2019s USMLE\u00ae Step 1 question of the day focuses on identifying the vascular structure most likely affected in an elderly patient with acute neurological deficits. What\u2019s the answer? Let\u2019s find out!<\/em><\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">An 85-year-old man is brought to the emergency room after being found on the floor in his home. Past medical history is significant for hypertension and hyperlipidemia. Temperature is 37.7\u00b0C (99.8\u00b0F), pulse is 101\/min, respirations are 22\/min, and blood pressure is 188\/94 mmHg. The patient appears conscious, but does not demonstrate spontaneous movement of the extremities and is unable to respond to voice or painful stimuli. The patient is able to blink and eye movements are restricted to the vertical plane. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Magnetic resonance angiogram will <em>most likely<\/em> reveal ischemia of which of the following vascular structures?\u00a0\u00a0<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>A. Posterior inferior cerebellar artery<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>B. Anterior spinal artery<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>C. Anterior inferior cerebellar artery<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>D. Basilar artery<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>E. Posterior cerebral artery<\/strong><\/p>\n\n\n\n<p class=\"has-text-align-center wp-block-paragraph\"><em>Scroll down for the correct answer!<\/em><\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"Osmosis.org at the University College London, UK\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/DIp3u0oTLo4?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"The_correct_answer_to_todays_USMLE%C2%AE_Step_1_Question_is%E2%80%A6\"><\/span>The correct answer to today\u2019s USMLE\u00ae Step 1 Question is\u2026<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>D. Basilar artery<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Correct:<\/strong> See Main Explanation.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Incorrect_Answer_Explanations\"><\/span>Incorrect Answer Explanations<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>A. Posterior inferior cerebellar artery<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:<\/strong> Posterior inferior cerebellar artery occlusion results in lateral medullary (Wallenberg) syndrome characterized by vertigo\/nystagmus, ipsilateral cerebellar signs, loss of pain\/temperature sensation on the ipsilateral face and contralateral body, bulbar weakness, and Horner syndrome.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>B. Anterior spinal artery<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:<\/strong> Infarction of the paramedian branches of anterior spinal artery results in medial medullary syndrome, which typically presents with contralateral hemiparesis (lateral corticospinal tract), decreased contralateral proprioception (medial lemniscus), and ipsilateral tongue paralysis (hypoglossal nucleus).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>C. Anterior inferior cerebellar artery<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:<\/strong> Lateral pontine syndrome occurs secondary to occlusion of anterior inferior cerebellar artery (AICA). Patients typically present with signs of a lower motor neuron facial nerve lesion, vertigo\/nystagmus, ipsilateral cerebellar signs, loss of pain\/temperature sensation on the ipsilateral face and contralateral body, ipsilateral sensorineural loss, and Horner syndrome.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>E. Posterior cerebral artery<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:<\/strong> Posterior cerebral artery infarction typically results in contralateral hemianopia due to infarction of the visual cortex. The macula is often spared due to contralateral circulation from the middle cerebral artery.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Main_Explanation\"><\/span>Main Explanation<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">This patient&#8217;s inability to move the extremities, loss of horizontal eye movements with preserved consciousness, and loss of mouth, tongue, and facial movements, is consistent with <strong>locked-in syndrome (LIS), <\/strong>due to the<strong> occlusion of the basilar artery. <\/strong>The most vulnerable territory associated with this condition lies at the paramedian base of the pons.&nbsp;<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Clinical features consistent with locked-in syndrome include:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Quadriplegia<\/strong> and<strong> inability to speak or swallow<\/strong> due to the involvement of corticospinal and corticobulbar tracts\u00a0<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Preserved<\/strong> <strong>consciousness <\/strong>due to the sparing of the reticular formation\u00a0<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Loss of horizontal eye movement <\/strong>due to the involvement of ocular cranial nerve nuclei and paramedian pontine reticular formation\u00a0<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Voluntary blinking and vertical eye movements remain intact<\/strong>, which are controlled in the rostral portion of the brainstem<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Major_Takeaway\"><\/span>Major Takeaway&nbsp;<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Locked-in syndrome (LIS)<\/strong> is characterized by<strong> quadriplegia and inability to speak or swallow with retained consciousness.<\/strong> Patients with this condition often retain the ability to blink and vertical eye movements.\u00a0\u00a0<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Want_to_learn_more_about_this_topic\"><\/span>Want to learn more about this topic?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Read this Osmosis high-yield note:<\/strong> <a href=\"https:\/\/www.osmosis.org\/learn\/Anatomy_clinical_correlates:_Posterior_blood_supply_to_the_brain\">Anatomy clinical correlates: Posterior blood supply to the brain<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"References\"><\/span>References<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Bruno, M. A., Schnakers, C., Damas, F., Pellas, F., Lutte, I., Bernheim, J., &#8230; &amp; Laureys, S. (2009). Locked-in syndrome in children: report of five cases and review of the literature. Pediatric neurology, 41(4), 237-246.\u00a0<\/li>\n\n\n\n<li>Fix, J., &amp; Brueckner, J. (2009). High-yield neuroanatomy (4th ed.). Philadelphia, Pa.: Wolters Kluwer, Lippincott, Williams et Wilkins.<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-large\"><a href=\"https:\/\/www.osmosis.org\/plans\"><img loading=\"lazy\" decoding=\"async\" width=\"700\" height=\"250\" src=\"https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2025\/01\/Blog_Display_Ads_GENERAL3_2023.png?w=700\" alt=\"\" class=\"wp-image-5048\" srcset=\"https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2025\/01\/Blog_Display_Ads_GENERAL3_2023.png 700w, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2025\/01\/Blog_Display_Ads_GENERAL3_2023.png?resize=300,107 300w\" sizes=\"auto, (max-width: 700px) 100vw, 700px\" \/><\/a><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><em><strong>Want more USMLE\u00ae Step 1 practice questions? Try Osmosis from Elsevier today! Access your&nbsp;<em><a href=\"https:\/\/www.osmosis.org\/plans\" target=\"_blank\" rel=\"noreferrer noopener\">free trial<\/a><\/em>&nbsp;and discover why millions of current and future clinicians and caregivers love learning with us.<\/strong><\/em><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Explore a clinical case of acute neurological deficits in an elderly patient, focusing on identifying the affected brainstem vascular territory.<\/p>\n","protected":false},"author":204,"featured_media":7933,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[27,20,16,1366,1369,44],"tags":[1623,1622,1624,1626,1628,1621,1620,1625,664,1627],"class_list":["post-7931","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-medicine","category-exam-prep","category-do","category-questions","category-step-1-questions","category-step-1","tag-basilar-artery","tag-brainstem-stroke","tag-clinical-neurology","tag-locked-in-syndrome","tag-mri-angiogram","tag-neuroanatomy","tag-pontine-infarct","tag-stroke-syndromes","tag-usmle-step-1","tag-vascular-ischemia"],"yoast_head":"<!-- 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