Unlike Huntington's or Parkinson's Diseases, a stroke is not a specific neurodegenerative disorder. Instead, a 'stroke' refers to one of two ways in which circulatory problems can cause brain damage. If blood flow to all or part of the brain is interrupted, neural cells die for lack of oxygen. A stroke is caused by relatively small, localized problem with an artery within the brain itself. The other type of vascular damage is caused by stopping all blood flow to the brain, as can occur with heart attacks. This causes damage to cells in sensitive areas like the the CA1 region of the hippocampus, involved in forming new memories. This area lends itself to neural stem cell grafts because areas of the hippocampus are known to be actively growing new neurons.
Following an induced heart attack, grafts of neural stem cells to to the CA1 region in rats improves spatial learning compared to the rats which did not receive the graft. Spatial learning is one of the main functions of CA1 in rats. Interestingly, only rats that where housed in an enriched environment, where they had things to interact with, showed the improvement. This shows the importance of interaction between grafted neural stem cells and established cells. For more information on stem cells and spatial memory, see here.
The other type of vascular damage that can occur in the brain is a stroke, which occurs when an artery in the brain is damaged. This causes cell death in the area around that artery. Since the damage generally occurs in a distinct brain region, neural stem cells may be able to help these areas regain control. So far there has been some success in animal models of stroke. Grafts placed in the striatum show promise, as do cortical grafts. However, as with CA1, cortical grafts require the animals to be in enriched environments (Bjorklund and Lindvall 2000).