Chiropractors rely heavily on manipulating their patients' spines. This has benefits for some patients, but more than half of all patients suffer mild to moderate adverse effects after seeing a chiropractor. These are mostly local and referred pains that usually last for two to three days. Chiropractors often claim that these are necessary steps on the road to getting better. However, several hundred cases have been documented in which patients were seriously and often permanently damaged after chiropractic manipulations. What usually happens in these tragic instances is that, upon manipulation of the upper spine, an artery supplying the brain is overstretched and simply breaks up, leading to a stroke that can prove fatal.