Sometimes, aura occurs without a subsequent headache. This is known in modern classification as a typical aura without headache, or acephalgic migraine in previous classification, or commonly as a silent migraine. However, silent migraine can still produce debilitating symptoms, with visual disturbance, vision loss in half of both eyes, alterations in color perception, and other sensory problems, like sensitivity to light, sound, and odors, and aura sudden outbreak without headache can be scary. It can last from 15 to 30 minutes, usually no longer than 60 minutes, and it can recur or appear as an isolated event. Many report a sore feeling in the area where the migraine was, and some report impaired thinking for a few days after the headache has passed. The person may feel tired or "hung over" and have head pain, cognitive difficulties, gastrointestinal symptoms, mood changes, and weakness. According to one summary, "Some people feel unusually refreshed or euphoric after an attack, whereas others note depression and malaise." For some individuals this can vary each time.