{"id":28784,"date":"2026-01-09T15:01:32","date_gmt":"2026-01-09T20:01:32","guid":{"rendered":"https:\/\/www.stepwards.com\/?page_id=28784"},"modified":"2026-01-09T19:30:39","modified_gmt":"2026-01-10T00:30:39","slug":"atlas-of-cranial-nerves-oculomotor-nerve-cn-3","status":"publish","type":"page","link":"https:\/\/www.stepwards.com\/?page_id=28784","title":{"rendered":"Atlas Of Cranial Nerves: Oculomotor Nerve (CN 3)"},"content":{"rendered":"<div id=\"toc_container\" class=\"no_bullets\"><p class=\"toc_title\">Page Contents<\/p><ul class=\"toc_list\"><li><a href=\"#OVERVIEW\"><span class=\"toc_number toc_depth_1\">1<\/span> OVERVIEW<\/a><\/li><li><a href=\"#FUNCTION\"><span class=\"toc_number toc_depth_1\">2<\/span> FUNCTION<\/a><\/li><li><a href=\"#ORIGIN_CRANIAL_NERVE_3_BRAINSTEM_NUCLEI\"><span class=\"toc_number toc_depth_1\">3<\/span> ORIGIN: CRANIAL NERVE 3 BRAINSTEM NUCLEI<\/a><\/li><li><a href=\"#BRAINSTEM_COURSE\"><span class=\"toc_number toc_depth_1\">4<\/span> BRAINSTEM COURSE<\/a><\/li><li><a href=\"#CISTERNAL_COURSE\"><span class=\"toc_number toc_depth_1\">5<\/span> CISTERNAL COURSE<\/a><\/li><li><a href=\"#CAVERNOUS_COURSE\"><span class=\"toc_number toc_depth_1\">6<\/span> CAVERNOUS COURSE<\/a><\/li><li><a href=\"#PROXIMAL_ORBITAL_SEGMENT\"><span class=\"toc_number toc_depth_1\">7<\/span> PROXIMAL ORBITAL SEGMENT<\/a><\/li><\/ul><\/div>\n<h5><span id=\"OVERVIEW\"><span style=\"text-decoration: underline;\">OVERVIEW<\/span><\/span><\/h5>\n<p>This page organizes relevant information, anatomy, and pathology relating to the third cranial nerve (the oculomotor nerve).<\/p>\n<h5><span id=\"FUNCTION\"><span style=\"text-decoration: underline;\">FUNCTION<\/span><\/span><\/h5>\n<p>The third cranial nerve controls eye movements which are depicted in the figure below (which shows the views of the clinical facing the patient and performing a routine eye exam where the eyes move in the in the charactersitc &#8220;H&#8221; pattern).<\/p>\n<figure id=\"attachment_711\" aria-describedby=\"caption-attachment-711\" style=\"width: 1394px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM.png\" rel=\"attachment wp-att-711\"><img loading=\"lazy\" class=\" wp-image-711\" src=\"http:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM.png\" alt=\"Classic eye exam &quot;H&quot; test showing cranial nerves tested for specific ocular movements \" width=\"1404\" height=\"605\" srcset=\"https:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM.png 1958w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM-300x129.png 300w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM-768x331.png 768w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM-1024x441.png 1024w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM-100x43.png 100w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM-150x65.png 150w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM-200x86.png 200w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM-450x194.png 450w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM-600x259.png 600w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2015\/12\/Screen-Shot-2015-12-27-at-8.21.06-PM-900x388.png 900w\" sizes=\"(max-width: 1404px) 100vw, 1404px\" \/><\/a><figcaption id=\"caption-attachment-711\" class=\"wp-caption-text\">Classic eye exam &#8220;H&#8221; test showing cranial nerves tested for specific ocular movements. The motion of the eyes is depicted by the cranial nerve responsible for the movement.<\/figcaption><\/figure>\n<p><strong>**CN III innervates every muscle except for the Superior Oblique (CN IV) and the Lateral Rectus (CN VI), additionally\u00a0 it will control elevation of the eyelid and damage to the nerve causes dilation given its innervation from the Edinger-Westphal nucleus.\u00a0<\/strong><\/p>\n<h5><span id=\"ORIGIN_CRANIAL_NERVE_3_BRAINSTEM_NUCLEI\"><span style=\"text-decoration: underline;\">ORIGIN: CRANIAL NERVE 3 BRAINSTEM NUCLEI<\/span><\/span><\/h5>\n<p>The third cranial nerve begins first in the midbrain, where it is supplied by two nuclei:<\/p>\n<ol>\n<li><strong>The oculomotor nucleus:\u00a0<\/strong>this supplies somatic efferent fibers to the oculomotor nerve. It is located anterior\/ventral to the periaqueductal grey matter in the midbrain at the level of the superior colliculus. It is just inferior and dorsal to the level of the red nuclei (depending on the orientation of an axial slice).<\/li>\n<li><strong>The Edinger-Westphal nucleus: <\/strong>supplies parasympathetic fibers to the oculomotor nerve which synapse at the ciliary ganglion (it is immediately behind\/posterior to the oculomotor nucleus at the same level in the midbrain).<\/li>\n<\/ol>\n<p>To locate the general region of these nuclei, it is easiest to find the midbrain, look closely at the cerebral aqueduct, and scroll to the level of the superior colliculus (dorsal bumps will be appreciated along the midbrain). At this level the nuclei will be just anterior to the periaqueductal grey matter (on either medial side of the brainstem). This is depicted below.<\/p>\n<figure id=\"attachment_28792\" aria-describedby=\"caption-attachment-28792\" style=\"width: 1155px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.stepwards.com\/wp-content\/uploads\/2026\/01\/Screenshot-2026-01-09-at-3.44.58\u202fPM.png\"><img loading=\"lazy\" class=\" wp-image-28792\" src=\"http:\/\/www.stepwards.com\/wp-content\/uploads\/2026\/01\/Screenshot-2026-01-09-at-3.44.58\u202fPM.png\" alt=\"\" width=\"1165\" height=\"621\" srcset=\"https:\/\/www.stepwards.com\/wp-content\/uploads\/2026\/01\/Screenshot-2026-01-09-at-3.44.58\u202fPM.png 859w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2026\/01\/Screenshot-2026-01-09-at-3.44.58\u202fPM-300x160.png 300w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2026\/01\/Screenshot-2026-01-09-at-3.44.58\u202fPM-768x409.png 768w\" sizes=\"(max-width: 1165px) 100vw, 1165px\" \/><\/a><figcaption id=\"caption-attachment-28792\" class=\"wp-caption-text\">General location of the nuclei relevant to the the third cranial nerve on T1 and FLAIR imaging.<\/figcaption><\/figure>\n<p><strong>** Notably the fibers to the inferior rectus, inferior oblique, and medial rectus muscles supply the ipsilateral eye; fibers innervating the superior rectus muscle decussate and supply the contralateral eye. <\/strong><\/p>\n<p><strong>**The decussating fibers pass through the opposite superior rectus nucleus; thus damage to the right oculomotor nucleus might have bilateral superior rectus muscle involvement<\/strong><\/p>\n<h5><span id=\"BRAINSTEM_COURSE\"><span style=\"text-decoration: underline;\">BRAINSTEM COURSE<\/span><\/span><\/h5>\n<p>After receiving supply from both nuclei, the nerve courses anteriorly through the brainstem with fibers crossing through the red nucleus, and through the medial aspect of the substantia niagra before exiting the midbrain along the medial aspect of the cerebral peduncle.<\/p>\n<h5><span id=\"CISTERNAL_COURSE\"><span style=\"text-decoration: underline;\">CISTERNAL COURSE<\/span><\/span><\/h5>\n<p>After exiting along the medial aspect of the cerebral peduncle, the oculomotor nerve will travel through the interpeduncular cistern, and then along the lateral aspect of the suprasellar\/chiasmatic cistern before piercing the dura through the occulomotor cistern to enter the cavernous sinus.<\/p>\n<figure id=\"attachment_28796\" aria-describedby=\"caption-attachment-28796\" style=\"width: 1113px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.stepwards.com\/wp-content\/uploads\/2026\/01\/Screenshot-2026-01-09-at-4.25.01\u202fPM.png\"><img loading=\"lazy\" class=\" wp-image-28796\" src=\"http:\/\/www.stepwards.com\/wp-content\/uploads\/2026\/01\/Screenshot-2026-01-09-at-4.25.01\u202fPM.png\" alt=\"\" width=\"1123\" height=\"585\" srcset=\"https:\/\/www.stepwards.com\/wp-content\/uploads\/2026\/01\/Screenshot-2026-01-09-at-4.25.01\u202fPM.png 900w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2026\/01\/Screenshot-2026-01-09-at-4.25.01\u202fPM-300x156.png 300w, https:\/\/www.stepwards.com\/wp-content\/uploads\/2026\/01\/Screenshot-2026-01-09-at-4.25.01\u202fPM-768x400.png 768w\" sizes=\"(max-width: 1123px) 100vw, 1123px\" \/><\/a><figcaption id=\"caption-attachment-28796\" class=\"wp-caption-text\">The cisternal course of the oculomotor nerve as it exits the midbrain on FLAIR and SSFP imaging.<\/figcaption><\/figure>\n<h5><span id=\"CAVERNOUS_COURSE\"><span style=\"text-decoration: underline;\">CAVERNOUS COURSE<\/span><\/span><\/h5>\n<p>&nbsp;<\/p>\n<h5><\/h5>\n<h5><span id=\"PROXIMAL_ORBITAL_SEGMENT\"><span style=\"text-decoration: underline;\">PROXIMAL ORBITAL SEGMENT<\/span><\/span><\/h5>\n","protected":false},"excerpt":{"rendered":"<p>Page Contents1 OVERVIEW2 FUNCTION3 ORIGIN: CRANIAL NERVE 3 BRAINSTEM NUCLEI4 BRAINSTEM COURSE5 CISTERNAL COURSE6 CAVERNOUS COURSE7 PROXIMAL ORBITAL SEGMENT OVERVIEW This page organizes relevant information, anatomy, and pathology relating to the third cranial nerve (the oculomotor nerve). FUNCTION The third cranial nerve controls eye movements which are depicted in the figure below (which shows the &#8230; <a title=\"Atlas Of Cranial Nerves: Oculomotor Nerve (CN 3)\" class=\"read-more\" href=\"https:\/\/www.stepwards.com\/?page_id=28784\" aria-label=\"More on Atlas Of Cranial Nerves: Oculomotor Nerve (CN 3)\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":28782,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_mi_skip_tracking":false},"jetpack_shortlink":"https:\/\/wp.me\/P71awf-7ug","_links":{"self":[{"href":"https:\/\/www.stepwards.com\/index.php?rest_route=\/wp\/v2\/pages\/28784"}],"collection":[{"href":"https:\/\/www.stepwards.com\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.stepwards.com\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.stepwards.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.stepwards.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=28784"}],"version-history":[{"count":8,"href":"https:\/\/www.stepwards.com\/index.php?rest_route=\/wp\/v2\/pages\/28784\/revisions"}],"predecessor-version":[{"id":28798,"href":"https:\/\/www.stepwards.com\/index.php?rest_route=\/wp\/v2\/pages\/28784\/revisions\/28798"}],"up":[{"embeddable":true,"href":"https:\/\/www.stepwards.com\/index.php?rest_route=\/wp\/v2\/pages\/28782"}],"wp:attachment":[{"href":"https:\/\/www.stepwards.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=28784"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}