{"id":5453,"date":"2025-12-09T13:34:40","date_gmt":"2025-12-09T18:34:40","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/?post_type=chapter&#038;p=5453"},"modified":"2025-12-09T23:27:44","modified_gmt":"2025-12-10T04:27:44","slug":"motor-dysfunction-and-posturing-due-to-motor-pathway-damage","status":"web-only","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/chapter\/motor-dysfunction-and-posturing-due-to-motor-pathway-damage\/","title":{"raw":"11p8  Motor Dysfunction and Posturing due to Motor Pathway Damage","rendered":"11p8  Motor Dysfunction and Posturing due to Motor Pathway Damage"},"content":{"raw":"<h1><strong>Motor Pathways and Damage<\/strong><\/h1>\r\n<ul>\r\n \t<li><strong>Voluntary movement<\/strong>\u00a0involves a\u00a0<strong>two-neuron pathway<\/strong>:\r\n<ul>\r\n \t<li><strong>Upper motor neuron (UMN):<\/strong>\r\n<ul>\r\n \t<li>Originates in the\u00a0<strong>motor cortex<\/strong>.<\/li>\r\n \t<li>Sends signals down the\u00a0<strong>brainstem and spinal cord<\/strong>.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li><strong>Lower motor neuron (LMN):<\/strong>\r\n<ul>\r\n \t<li>Innervates muscles directly.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li><strong>Damage to the pathway<\/strong>:\r\n<ul>\r\n \t<li><strong>UMN damage<\/strong>: causes\u00a0<strong>spastic paralysis<\/strong>, hyperreflexia.<\/li>\r\n \t<li><strong>LMN damage<\/strong>: causes\u00a0<strong>flaccid paralysis<\/strong>.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h1><strong>Abnormal Posturing<\/strong><\/h1>\r\n<ul>\r\n \t<li><strong>Decorticate Posture<\/strong>:\r\n<ul>\r\n \t<li>Seen with\u00a0<strong>cerebral cortex damage<\/strong>.<\/li>\r\n \t<li><strong>Flexed arms<\/strong>,\u00a0<strong>adducted limbs<\/strong>,\u00a0<strong>flexed legs<\/strong>.<\/li>\r\n \t<li>Indicates\u00a0<strong>severe brain injury<\/strong>\u00a0at or above the brainstem.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li><strong>Decerebrate Posture<\/strong>:\r\n<ul>\r\n \t<li>Damage\u00a0<strong>below<\/strong>\u00a0the level of the\u00a0<strong>red nucleus<\/strong>\u00a0in the midbrain.<\/li>\r\n \t<li><strong>Extended arms and legs<\/strong>,\u00a0<strong>arched back<\/strong>.<\/li>\r\n \t<li>Often associated with\u00a0<strong>brainstem injury<\/strong>.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li><strong>Opisthotonos (damage to extrapyramidal tract)<\/strong>: spastic paralysis in spinal muscles (rigid, arched back)<\/li>\r\n \t<li><strong>Mixed (hemiplegic)<\/strong>:\r\n<ul>\r\n \t<li>One side\u00a0<strong>flexed<\/strong>\u00a0(decorticate), one side\u00a0<strong>extended<\/strong>\u00a0(decerebrate).<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h1><strong>Somatic Motor Nerve Pathways &amp; Symptoms<\/strong><\/h1>\r\n<ul>\r\n \t<li><strong>UMN damage<\/strong>:\r\n<ul>\r\n \t<li>Causes either <strong>flaccid<\/strong> or <strong>spastic paralysis (depending on brain lesion) <\/strong>on the <strong>contralateral (opposite) side <\/strong>of the <strong>body<\/strong>.<\/li>\r\n \t<li>Hyperactive reflexes (<strong>hyperreflexia<\/strong>).<\/li>\r\n \t<li><strong>Positive<\/strong> (Abnormal) <strong>Babinski sign<\/strong> (flared toes in individuals older than infants)<\/li>\r\n \t<li><strong>Clonus<\/strong>: repetitive muscle contractions.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n&nbsp;\r\n<ul>\r\n \t<li><strong>LMN damage<\/strong>:\r\n<ul>\r\n \t<li>Causes\u00a0<strong>flaccid paralysis<\/strong> on<strong> ipsilateral (same) side of body<\/strong>.<\/li>\r\n \t<li>Muscle weakness, atrophy.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h1><strong>Reflexes and Signs of Brain Damage<\/strong><\/h1>\r\n<ol>\r\n \t<li><strong>Babinski Sign<\/strong><\/li>\r\n<\/ol>\r\n<ul>\r\n \t<li><strong>Normal in infants<\/strong>:\r\n<ul>\r\n \t<li>Stroking lateral side of foot causes\u00a0<strong>toes to flare<\/strong>.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li><strong>Pathologic in adults<\/strong>:\r\n<ul>\r\n \t<li>Same stimulus causes\u00a0<strong>toes to curl downward<\/strong>\u00a0(negative Babinski).<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li><strong>Implication<\/strong>:\r\n<ul>\r\n \t<li>Flaring toes indicates damage to\u00a0<strong>UMN pathways<\/strong>.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<ol start=\"2\">\r\n \t<li><strong>Hyperreflexia<\/strong><\/li>\r\n<\/ol>\r\n<ul>\r\n \t<li>Exaggerated reflexes (e.g.,\u00a0<strong>patellar reflex<\/strong>).<\/li>\r\n \t<li>Might be accompanied by\u00a0<strong>clonus<\/strong>\u00a0(repetitive contraction).<\/li>\r\n \t<li>Indicates\u00a0<strong>UMN<\/strong>\u00a0lesion.<\/li>\r\n<\/ul>\r\n<h1><strong>Summary<\/strong><\/h1>\r\n<ul>\r\n \t<li><strong>Damage<\/strong>\u00a0to\u00a0<strong>cortical or brainstem pathways<\/strong>\u00a0produces characteristic postures and reflex changes.<\/li>\r\n \t<li><strong>Signs<\/strong>\u00a0like\u00a0<strong>Babinski<\/strong>\u00a0and\u00a0<strong>hyperreflexia<\/strong>\u00a0help localize lesions.<\/li>\r\n \t<li>Presence of reflexes indicates\u00a0<strong>brainstem integrity<\/strong>, critical in coma assessment.<\/li>\r\n<\/ul>","rendered":"<h1><strong>Motor Pathways and Damage<\/strong><\/h1>\n<ul>\n<li><strong>Voluntary movement<\/strong>\u00a0involves a\u00a0<strong>two-neuron pathway<\/strong>:\n<ul>\n<li><strong>Upper motor neuron (UMN):<\/strong>\n<ul>\n<li>Originates in the\u00a0<strong>motor cortex<\/strong>.<\/li>\n<li>Sends signals down the\u00a0<strong>brainstem and spinal cord<\/strong>.<\/li>\n<\/ul>\n<\/li>\n<li><strong>Lower motor neuron (LMN):<\/strong>\n<ul>\n<li>Innervates muscles directly.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<li><strong>Damage to the pathway<\/strong>:\n<ul>\n<li><strong>UMN damage<\/strong>: causes\u00a0<strong>spastic paralysis<\/strong>, hyperreflexia.<\/li>\n<li><strong>LMN damage<\/strong>: causes\u00a0<strong>flaccid paralysis<\/strong>.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h1><strong>Abnormal Posturing<\/strong><\/h1>\n<ul>\n<li><strong>Decorticate Posture<\/strong>:\n<ul>\n<li>Seen with\u00a0<strong>cerebral cortex damage<\/strong>.<\/li>\n<li><strong>Flexed arms<\/strong>,\u00a0<strong>adducted limbs<\/strong>,\u00a0<strong>flexed legs<\/strong>.<\/li>\n<li>Indicates\u00a0<strong>severe brain injury<\/strong>\u00a0at or above the brainstem.<\/li>\n<\/ul>\n<\/li>\n<li><strong>Decerebrate Posture<\/strong>:\n<ul>\n<li>Damage\u00a0<strong>below<\/strong>\u00a0the level of the\u00a0<strong>red nucleus<\/strong>\u00a0in the midbrain.<\/li>\n<li><strong>Extended arms and legs<\/strong>,\u00a0<strong>arched back<\/strong>.<\/li>\n<li>Often associated with\u00a0<strong>brainstem injury<\/strong>.<\/li>\n<\/ul>\n<\/li>\n<li><strong>Opisthotonos (damage to extrapyramidal tract)<\/strong>: spastic paralysis in spinal muscles (rigid, arched back)<\/li>\n<li><strong>Mixed (hemiplegic)<\/strong>:\n<ul>\n<li>One side\u00a0<strong>flexed<\/strong>\u00a0(decorticate), one side\u00a0<strong>extended<\/strong>\u00a0(decerebrate).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h1><strong>Somatic Motor Nerve Pathways &amp; Symptoms<\/strong><\/h1>\n<ul>\n<li><strong>UMN damage<\/strong>:\n<ul>\n<li>Causes either <strong>flaccid<\/strong> or <strong>spastic paralysis (depending on brain lesion) <\/strong>on the <strong>contralateral (opposite) side <\/strong>of the <strong>body<\/strong>.<\/li>\n<li>Hyperactive reflexes (<strong>hyperreflexia<\/strong>).<\/li>\n<li><strong>Positive<\/strong> (Abnormal) <strong>Babinski sign<\/strong> (flared toes in individuals older than infants)<\/li>\n<li><strong>Clonus<\/strong>: repetitive muscle contractions.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<ul>\n<li><strong>LMN damage<\/strong>:\n<ul>\n<li>Causes\u00a0<strong>flaccid paralysis<\/strong> on<strong> ipsilateral (same) side of body<\/strong>.<\/li>\n<li>Muscle weakness, atrophy.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h1><strong>Reflexes and Signs of Brain Damage<\/strong><\/h1>\n<ol>\n<li><strong>Babinski Sign<\/strong><\/li>\n<\/ol>\n<ul>\n<li><strong>Normal in infants<\/strong>:\n<ul>\n<li>Stroking lateral side of foot causes\u00a0<strong>toes to flare<\/strong>.<\/li>\n<\/ul>\n<\/li>\n<li><strong>Pathologic in adults<\/strong>:\n<ul>\n<li>Same stimulus causes\u00a0<strong>toes to curl downward<\/strong>\u00a0(negative Babinski).<\/li>\n<\/ul>\n<\/li>\n<li><strong>Implication<\/strong>:\n<ul>\n<li>Flaring toes indicates damage to\u00a0<strong>UMN pathways<\/strong>.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<ol start=\"2\">\n<li><strong>Hyperreflexia<\/strong><\/li>\n<\/ol>\n<ul>\n<li>Exaggerated reflexes (e.g.,\u00a0<strong>patellar reflex<\/strong>).<\/li>\n<li>Might be accompanied by\u00a0<strong>clonus<\/strong>\u00a0(repetitive contraction).<\/li>\n<li>Indicates\u00a0<strong>UMN<\/strong>\u00a0lesion.<\/li>\n<\/ul>\n<h1><strong>Summary<\/strong><\/h1>\n<ul>\n<li><strong>Damage<\/strong>\u00a0to\u00a0<strong>cortical or brainstem pathways<\/strong>\u00a0produces characteristic postures and reflex changes.<\/li>\n<li><strong>Signs<\/strong>\u00a0like\u00a0<strong>Babinski<\/strong>\u00a0and\u00a0<strong>hyperreflexia<\/strong>\u00a0help localize lesions.<\/li>\n<li>Presence of reflexes indicates\u00a0<strong>brainstem integrity<\/strong>, critical in coma assessment.<\/li>\n<\/ul>\n","protected":false},"author":1370,"menu_order":14,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["zoe-soon"],"pb_section_license":"cc-by-nc-sa"},"chapter-type":[],"contributor":[60],"license":[57],"class_list":["post-5453","chapter","type-chapter","status-web-only","hentry","contributor-zoe-soon","license-cc-by-nc-sa"],"part":76,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5453","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/users\/1370"}],"version-history":[{"count":4,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5453\/revisions"}],"predecessor-version":[{"id":5551,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5453\/revisions\/5551"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/parts\/76"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5453\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/media?parent=5453"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapter-type?post=5453"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/contributor?post=5453"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/license?post=5453"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}