77 healthy volunteers without any other primary headache disorder were included into this study. 44/77 (57%) volunteers had a previous history of HICS.
Two protocols for provoking HICS were tested.
(1) Solid ice test (Selekler et al., 2004): Volunteers were asked to press a trapezoid ice cube to the hard palate (contact time 90 s, temperature −16 °C).
(2) Ice water test: Volunteers were asked to drink 200 mL of ice water (temperature 0 °C) as fast as possible.
Subsequently the clinical features of the provoked headaches were inquired.
The ice water stimulus provoked HICS significantly more often than the ice cube stimulus (OR 7.75, 95% CI 3.39–17.72, p<0.001, χ2). Latency and duration of HICS during the ice water protocol were shorter than during the ice cube protocol. Headache character was different between ice cube stimulation and ice water stimulation (Table 1). Localisation did not differ between the two protocols (Fig. 1). A second headache attack followed in 10/39 (26%) volunteers after ice water intake. Lacrimation occurred more often in volunteers with HICS than in volunteers without HICS.
The ice water stimulus provoked HICS significantly more often than the ice cube stimulus. HICS provoked by ice water had a shorter latency, shorter duration, different pain character and higher pain intensity than HICS provoked by ice cubes. Spatial extent, spatial summation and a high intake speed, achieved by drinking ice water, seem to be more important than temperature alone for HICS induction. The different properties of the cold stimuli might also explain the different latencies of HICS occurrence between the two protocols. Another explanation might be that there are two types of HICS (an early onset short lasting and a late onset longer lasting type) as proposed previously (Bird et al., 1992). The present findings of two subsequent HICS in the same volunteers and differences of pain quality between ice cube stimulation and ice water stimulation support and extend this notion. Lacrimation during HICS indicates strong activation of the trigeminal autonomic reflex in HICS.