<unk> s are recurring bouts of severe unilateral headache attacks. The duration of a typical CH attack ranges from about 15 to 180 minutes. About 75% of untreated attacks last less than 60 minutes. However, females may have longer and more severe CH. The onset of an attack is rapid and typically without an aura. Preliminary sensations of pain in the general area of attack, referred to as "shadows", may signal an imminent CH, or these symptoms may linger after an attack has passed, or between attacks. Though CH is strictly unilateral, there are some documented cases of "side-shift" between<unk>  periods, or, rarely, simultaneous (within the same<unk>  period) bilateral<unk> s. Pain The pain occurs only on one side of the head, around the eye, particularly behind or above the eye, in the temple. The pain is typically greater than in other headache conditions, including migraines, and is usually described as burning, stabbing, drilling or squeezing. While suicide is rare, those with<unk> s may experience suicidal thoughts (giving the alternative name "suicide headache" or "suicidal headache"). The pain of CH is remarkably greater than in other headache conditions, including severe migraine. The term "headache" does not adequately convey the severity of the condition; the disease may be the most painful condition known to medical science. Dr. Peter Goadsby, Professor of Clinical Neurology at University College London, a leading researcher on the condition has commented:<unk>  is probably the worst pain that humans experience. I know that’s quite a strong remark to make, but if you ask a<unk>  patient if they’ve had a worse experience, they’ll universally say they haven't. Women with<unk>  will tell you that an attack is worse than giving birth. So you can imagine that these people give birth without anesthetic once or twice a day, for six, eight, or ten weeks at a time, and then have a break. It's just awful." Other symptoms The typical symptoms of<unk>  include grouped occurrence and recurrence<unk>  of headache attack, severe unilateral orbital, supraorbital and/or temporal pain. If left untreated, attack frequency may range from one attack every two days to eight attacks per day.<unk>  attack is accompanied by at least one of the following autonomic symptoms: drooping eyelid, pupil constriction, redness of the conjunctiva, tearing, runny nose and less commonly, facial blushing, swelling, or sweating, typically appearing on the same side of the head as the pain. Similar to a migraine, sensitivity to light (photophobia) or noise (phonophobia) may occur during a CH. Nausea is a rare symptom although it has been reported. Restlessness (for example, pacing or rocking back and forth) may occur. Secondary effects may include the inability to organize thoughts and plans, physical exhaustion, confusion, agitation, aggressiveness, depression, and anxiety. People with CH may dread facing another headache and adjust their physical or social activities around a possible future occurrence. Likewise they may seek assistance to accomplish what would otherwise be normal tasks. They may hesitate to make plans because of the regularity, or conversely, the unpredictability of the pain schedule. These factors can lead to generalized anxiety disorders, panic disorder, serious depressive disorders, social withdrawal and isolation.<unk> s have been recently associated with obstructive sleep apnea comorbidity. Recurrence<unk> s may occasionally be referred to as "alarm clock headache" because of the regularity of their recurrence. CH attacks often awaken individuals from sleep. Both individual attacks and the<unk>  grouping can have a metronomic regularity; attacks typically striking at a precise time of day each morning or night. The recurrence of headache<unk>  grouping may occur more often around solstices, or seasonal changes, sometimes showing circannual periodicity. Conversely, attack frequency may be highly unpredictable, showing no periodicity at all. These observations have prompted researchers to speculate an involvement or dysfunction of the hypothalamus. The hypothalamus controls the body's "biological clock" and circadian rhythm. In episodic<unk> , attacks occur once or more daily, often at the same time each day for a period of several weeks, followed by a headache-free period lasting weeks, months, or years. Approximately 10–15% of<unk> s are chronic, with multiple headaches occurring every day for years, sometimes without any remission. In accordance with the International Headache Society (IHS) diagnostic criteria,<unk> s occurring in two or more<unk>  periods, lasting from 7 to 365 days with a pain-free remission of one month or longer between the headache attacks may be classified as episodic. If headache attacks occur for more than a year without pain-free remission of at least one month, the condition is classified as chronic. Chronic CH both occurs and recurs without any remission periods between cycles; there may be variation in cycles, meaning the frequency and severity of attacks may change without predictability for a period of time. The frequency, severity, and duration of headache attacks experienced by people during these cycles varies between individuals and does not demonstrate complete remission of the episodic form. The condition may change unpredictably from chronic to episodic and from episodic to chronic.
Cluster headache
Migraine
Lupus headache
Trigeminal neuralgia
Vascular headache
Trigeminal autonomic cephalgia
Tension headache
Medication overuse headache