The single largest cause of adult disability in the developed world is ischemic stroke, in which blood flow in or to the brain is blocked. It precipitates immense amounts of social and financial costs. Currently, therapies for stroke focus on prevention or acute phase treatments that arrest the stroke while it is happening. But many patients are not fortunate enough to get acute phase treatment and suffer neurological damage that leads to functional and cognitive impairment. Until now, there have been almost no options for such patients. But last February, a company called ReNeuron received approval to begin a clinical trial of neural stem cell therapy for disabled stroke patients . Two patients have been treated thus far and the therapy appears to be safe.