{"id":1902,"date":"2023-01-14T14:26:00","date_gmt":"2023-01-14T14:26:00","guid":{"rendered":"https:\/\/www.osmosis.org\/blog\/?p=1902"},"modified":"2026-02-19T16:53:26","modified_gmt":"2026-02-20T00:53:26","slug":"usmle-step-2-ck-question-of-the-day-routes-of-infection","status":"publish","type":"post","link":"https:\/\/www.osmosis.org\/blog\/usmle-step-2-ck-question-of-the-day-routes-of-infection","title":{"rendered":"USMLE\u00ae Step 2 CK Question of the Day: Routes of infection"},"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-2-ck-question-of-the-day-routes-of-infection\/#The_correct_answer_to_todays_USMLE%C2%AE_Step_2_CK_Question_is%E2%80%A6\" >The correct answer to today&#8217;s USMLE\u00ae Step 2 CK Question is&#8230;<\/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-2-ck-question-of-the-day-routes-of-infection\/#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-2-ck-question-of-the-day-routes-of-infection\/#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-2-ck-question-of-the-day-routes-of-infection\/#Major_Takeaway\" >Major Takeaway<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-2-ck-question-of-the-day-routes-of-infection\/#References\" >References<\/a><\/li><\/ul><\/nav><\/div>\n\n<p class=\"wp-block-paragraph\"><em>Today&#8217;s <em><strong>USMLE\u00ae Step 2 CK Question of the Day<\/strong><\/em> involves a child who&#8217;s evaluated on inpatient rounds for a retropharyngeal abscess, and the physician tells his parents that urgent treatment is needed. Do you know why? Let&#8217;s find out!<\/em><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A <strong>5-year-old boy<\/strong> is evaluated on inpatient rounds for a <strong>retropharyngeal abscess.<\/strong> <strong>Temperature is 102 \u00b0F, pulse is 122\/min, respiratory rate is 20\/min.<\/strong> The patient is <strong>awake <\/strong>and <strong>oriented <\/strong>and <strong>appears tired.<\/strong> He&#8217;s <strong>not struggling to breathe<\/strong> and is otherwise <strong>resting comfortably.<\/strong> An area of <strong>erythematous inflammation<\/strong> is seen in the <strong>posterior oropharynx,<\/strong> and the patient has mild <strong>submandibular lymphadenopathy.<\/strong> Parenteral antibiotic therapy is initiated with <strong>clindamycin <\/strong>and <strong>metronidazole<\/strong>. The physician explains to the parents at the bedside that urgent treatment is required due to the potential spread of infection into a region called the \u201cdanger space.\u201d <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Which of the following <em>best describes<\/em> the boundaries of this space?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>A. Buccopharyngeal fascia anteriorly and alar fascia posteriorly<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>B. Buccopharyngeal fascia anteriorly and prevertebral fascia posteriorly<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>C. Pretracheal fascia anteriorly and alar fascia posteriorly<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>D. Alar fascia anteriorly and prevertebral fascia posteriorly<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"The_correct_answer_to_todays_USMLE%C2%AE_Step_2_CK_Question_is%E2%80%A6\"><\/span>The correct answer to today&#8217;s USMLE\u00ae Step 2 CK Question is<strong>&#8230;<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>D. Alar fascia anteriorly and prevertebral fascia posteriorly<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><em>Before we get to the Main Explanation, let&#8217;s see why the answer wasn&#8217;t A, B, C, or E. Skip to the bottom if you want to see the correct answer right away!<\/em><\/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. Buccopharyngeal fascia anteriorly and alar fascia posteriorly<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:<\/strong>&nbsp;These are the boundaries of the retropharyngeal space. The \u2018danger space\u2019 is posterior to the retropharyngeal space and bounded anteriorly by the alar fascia and posteriorly by the prevertebral fascia.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>B. Buccopharyngeal fascia anteriorly and prevertebral fascia posteriorly<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:&nbsp;<\/strong>The \u2018danger space\u2019 is posterior to the retropharyngeal space and bounded anteriorly by the alar fascia and posteriorly by the prevertebral fascia.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>C. Pretracheal fascia anteriorly and alar fascia posteriorly<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:&nbsp;<\/strong>The \u2018danger space\u2019 is posterior to the retropharyngeal space and bounded anteriorly by the alar fascia and posteriorly by the prevertebral fascia.<\/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\">Posterior to the pharynx, there is a potential space called the&nbsp;<strong>retropharyngeal space<\/strong>. This space is bounded anteriorly by the buccopharyngeal fascia, the superior continuation of the pretracheal fascia, and posteriorly by the alar fascia. Infection in the retropharyngeal space can also lead to a retropharyngeal abscess, resulting in difficulty swallowing and speaking.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Another important space is the \u2018<strong>danger space<\/strong>,\u2019 which is&nbsp;<strong>posterior to the&nbsp;<\/strong><strong>retropharyngeal space<\/strong>&nbsp;and bounded anteriorly by the alar fascia and posteriorly by the prevertebral layer of the deep cervical fascia. This space extends from the base of the skull into the&nbsp;<strong>posterior mediastinum<\/strong>&nbsp;and down to the level of the diaphragm, making it the most important route for the spread of infection between the neck and thorax.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" height=\"583\" width=\"1024\" src=\"https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/09\/2024-09-11T083107.865.png?w=1024\" alt=\"SPACES\n&quot;Danger Space&quot;\n*Posterior to retropharyngeal space\nBoundaries\nAnterior: Alar fascia\nPosterior: Prevertebral layer\nSuperior: *Base of skull\nInferior: *posterior mediastinum to diaphram\n!! Most important route for spread of infection between neck and thorax\n\nImages of a transverse section of the neck through C7 and a view of the midsagittal section.\" class=\"wp-image-1904\" srcset=\"https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/09\/2024-09-11T083107.865.png 1514w, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/09\/2024-09-11T083107.865.png?resize=300,171 300w, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/09\/2024-09-11T083107.865.png?resize=768,437 768w, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/09\/2024-09-11T083107.865.png?resize=1024,583 1024w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Major_Takeaway\"><\/span>Major Takeaway<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>The &#8220;danger&#8221; space lies posterior to the retropharyngeal space. It&#8217;s bounded by the alar fascia anteriorly and the prevertebral fascia posteriorly. It&#8217;s a potential space that provides a path for retropharyngeal infections to extend from the neck into the mediastinum in the thorax.<\/strong><\/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>Mnatsakanian A, Minutello K, Bordoni B. Anatomy, Head and Neck, Retropharyngeal Space. [Updated 2021 Jul 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: <a href=\"https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK537044\/\">https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK537044\/<\/a><\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><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\/02\/Blog_Display_Ads_GENERAL2_2023.png\" alt=\"\" class=\"wp-image-5441\" srcset=\"https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2025\/02\/Blog_Display_Ads_GENERAL2_2023.png 700w, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2025\/02\/Blog_Display_Ads_GENERAL2_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><em>Try <strong>Osmosis from Elsevier <\/strong>today! Access your\u00a0<\/em><a href=\"https:\/\/www.osmosis.org\/login?type=create\" target=\"_blank\" rel=\"noreferrer noopener\"><em><strong>free\u00a0trial<\/strong><\/em><\/a><em>\u00a0and find out why millions of <strong>clinicians and caregivers love learning by Osmosis<\/strong>.<\/em><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Prep for the USMLE\u00ae Step 2 CK exam with today&#8217;s question focused on a 5-year-old boy presenting with a retropharyngeal abscess. Learn to identify the anatomical boundaries of the &#8220;danger space&#8221; and understand the urgency of managing such infections. Strengthen your clinical knowledge and improve your diagnostic skills for effective patient care!<\/p>\n","protected":false},"author":202,"featured_media":1903,"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":[27,20,1370,45],"tags":[346,343,669,265,516,448,245,667,668,670,185,671],"class_list":["post-1902","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-medicine","category-exam-prep","category-step-2-questions","category-step-2","tag-anatomy","tag-clinical-assessment","tag-emergency-care","tag-healthcare-training","tag-infection-control","tag-medical-diagnosis","tag-nursing-education","tag-pediatric-medicine","tag-retropharyngeal-abscess","tag-step-2-ck","tag-usmle","tag-usmle-step-2"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v23.6 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>USMLE\u00ae Step 2 CK Question of the Day: Routes of infection - Osmosis Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-2-ck-question-of-the-day-routes-of-infection\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"USMLE\u00ae Step 2 CK Question of the Day: Routes of infection - Osmosis Blog\" \/>\n<meta property=\"og:description\" content=\"Prep for the USMLE\u00ae Step 2 CK exam with today&#039;s question focused on a 5-year-old boy presenting with a retropharyngeal abscess. 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