Question 1308
{"accessible":true,"alternatives":[{"id":6534,"text":"demyelination"},{"id":6535,"text":"direct trauma"},{"id":6536,"text":"Kernohan notch phenomenon"},{"id":6537,"text":"midbrain infarction"},{"id":6538,"text":"tumor infiltration"},{"id":6539,"text":"Wallerian degeneration"}],"archived":false,"correctAlternativeId":6539,"explanation":"\u003cp\u003eThis patient had a previous left middle cerebral artery territory infarct (shown in the right-sided image) with resultant\u0026nbsp;Wallerian degeneration\u0026nbsp;of the corticospinal tracts. This results in a reduction in the volume of the ipsilateral cerebral peduncle.\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003ca href=\"/articles/wallerian-degeneration\" title=\"Wallerian degeneration\"\u003eWallerian degeneration\u003c/a\u003e is the process of antegrade degeneration of the axons and their accompanying myelin sheaths following proximal axonal or neuronal cell body lesions. It may result following neuronal loss due to cerebral infarction, trauma, necrosis, focal demyelination, or hemorrhage.\u0026nbsp;\u003c/p\u003e\u003cp\u003eIn contrast, Kernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect, resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli.\u003c/p\u003e","id":1308,"imageUrl":"https://prod-images-static.radiopaedia.org/multiple_choice_questions/6/4_big_gallery.jpeg","imageAttribution":{"kind":"case","rID":5128},"imageAttributionCaseInfo":{"title":"Wallerian degeneration","contributor_name":"Frank Gaillard","contributor_param":"frank","case_rid":5128,"case_param":"wallerian-degeneration"},"firstQuestionPath":"/questions/2590","nextQuestionPath":null,"relatedArticles":[{"id":18998,"title":"Wallerian degeneration","link":"/articles/wallerian-degeneration?lang=us"},{"id":1617,"title":"Middle cerebral artery (MCA) infarct","link":"/articles/middle-cerebral-artery-mca-infarct?lang=us"},{"id":10990,"title":"Kernohan phenomenon","link":"/articles/kernohan-phenomenon?lang=us"}],"alsoUsedIn":[{"id":771,"kind":"Course","title":"Stroke Learning Pathway - page 771","link":"https://radiopaedia.org/courses/stroke-learning-pathway/pages/771"},{"id":2108,"kind":"Course","title":"Stroke Learning Pathway - peer review - page 2108","link":"https://radiopaedia.org/courses/stroke-learning-pathway-peer-review/pages/2108"}],"stem":"\u003cp\u003eWhat is the cause of the midbrain abnormality indicated by the orange arrow?\u003c/p\u003e","menuLinks":[{"text":"Report problem with question","url":"https://docs.google.com/forms/d/e/1FAIpQLSfO3soWYhOjJ7yErSysyCe5V4A1CqW7WK3rDA7MtAkecMGqNw/viewform?entry.1624461248\u0026entry.553583435=https://radiopaedia.org/questions/1308"}],"attemptsPercentages":[{"alternativeId":"6537","percentage":8},{"alternativeId":"6534","percentage":2},{"alternativeId":"6536","percentage":10},{"alternativeId":"6539","percentage":79},{"alternativeId":"6535","percentage":0},{"alternativeId":"6538","percentage":1}],"promptToLogin":false,"questionManager":false,"articleId":"brainstem-stroke-syndromes"}