Just what causes the temporal arteries to become inflamed isn't known. In some cases, the swelling affects just part of an artery with sections of normal vessel in between.
Symptoms include headache, scalp tenderness, jaw pain, blurred or double vision, and sudden loss of vision in one eye. Head pain can get increasingly worse, can come and go, or can stop temporarily.
The condition needs prompt treatment with corticosteroid drugs to prevent permanent vision loss.