Stroke is a result of the aortic dissection.
http://www.emedicine.com/radio/topic43.htm
"Occlusion of aortic branch vessels from aortic dissection may result in stroke, renal failure, mesenteric ischemia, lower extremity ischemia, and paraplegia (caused by obstruction of the spinal artery)."
FYI. Looks like Mae was as terminal as her La Grange physician stated.