What is giant cell arteritis? Giant cell arteritis causes the arteries of the scalp and neck to become red, hot, swollen, or painful. The arteries most affected are those in the temples on either side of the head. These arteries narrow, so not enough blood can pass through. It is important that you get treatment right away. Otherwise, the arteries could be permanently damaged. There is also a risk of blindness or stroke. If you have giant cell arteritis, your doctor should also look for signs of another disorder, polymyalgia rheumatica. These conditions often occur together.