1 If a lot of blood leaks out, it can cause a buildup of pressure in the brain because the brain is enclosed in the skull. There is no room for brain tissue to expand, and so the leaked blood can compress and kill important areas of the brain.  Hemorrhagic strokes tend to be more serious than ischemic strokes.
Horizontal definition, at right angles to the vertical; parallel to level ground. See more.
When you're standing up, you're vertical, as opposed to when you lie down in a horizontal position on the couch. The terms vertical and horizontal often describe directions: a vertical line goes up and down, and a horizontal line goes across.