Characteristics of Pain
The pain of a cluster headache commences quickly, without warning, and reaches a crescendo within 2 to 15 minutes. It is often excruciating in intensity, and is deep, nonfluctuating, and explosive in quality; only occasionally is it pulsatile. In addition, 10 to 20 percent of patients report superimposed paroxysms of stabbing, icepick-like pains in the periorbital region that last for a few seconds and may occur once or several times in rapid succession; this paroxysmal pain usually heralds the end of an attack. The symptoms resolve in 1 to 2 minutes (Ekbom, 1975).
The pain usually begins in, around, or above the eye or the temple (Fig. 6-3); occasionally the face, neck, ear, or hemicranium may be affected (Sutherland and Eadie, 1972). It is always unilateral, and generally affects the same side in subsequent bouts. However, it may shift to the corresponding region of the opposite side in 15 percent of patients (Manzoni et al, 1983b), usually for the duration of a bout, less often switching sides within a bout. Many patients prefer to be upright and active when an attack is in progress, but this is reported with a frequency that is not high enough to be useful diagnostically (Russell, 1981).
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Periodicity and Duration of the Attacks
Attacks last from 30 minutes to 2 hours (mean of 45 minutes) in about 75 percent of cases. Occasionally, attacks - especially mild ones - may be as short as 10 minutes, whereas others may last as long as several hours. Attacks range in frequency from six per 24 hours to one per week, with a mean of one to two per day. Periodicity is a characteristic feature in about 85 percent of patients: attacks of pain tend to recur at the same hour each day for the duration of the cluster bout; many individuals also experience additional attacks that occur randomly throughout the day. About 75 percent of attacks occur between 9 p.m. and 10 a.m. (Russell, 1981). Manzoni et al, (1983b) found sharp peaks for attack frequency between 1 and 2 a.m., 1 and 3 p.m., and at 9 p.m (Fig. 6-4). Patients are awakened from sleep by pain paroxysms in about 50 percent of cases, usually within 2 hours of falling asleep (Lance and Anthony, 1971; Hornabrook, 1964). Nocturnal attacks are associated with rapid eye movement (REM) sleep about one-half the time in episodic cluster headache, but only rarely in the chronic form (Plaffenrath et al, 1986; Kayed and Sjaastad, 1985).