We aimed to estimate primary sensory evoked potential (EP) amplitude, amplitude-intensity functions and habituation in migraine patients compared with healthy control subjects and to investigate the possible relation to check size, sound and light discomfort thresholds, and the time to the next attack. Amplitudes of cortical visual evoked potentials (VEP, check size 8' and 33'), cortical long latency auditory evoked potential (AEP NIP1; 40, 55 and 70 dB SL tones) and brainstem auditory evoked potential (BAEP wave IV-V; 40, 55 and 65 dB SL clicks) were recorded and analysed in a blind and balanced design. The difference between the response to the first and the second half of the stimulus sequence was used as a measure of habituation. Twenty-one migraine patients (16 women and five men, mean age 39.3 years, six with aura, 15 without aura) and 22 sex- and age-matched healthy control subjects were studied (18 women and four men, mean age 39.5 years). Low sound discomfort threshold correlated significantly with low levels of BAEP wave IV-V amplitude habituation (r = -0.30, P = 0.05). VEP an AEP amplitudes, habituation, and amplitude-intensity function (ASF) slopes did not differ between groups when ANOVA main factors were considered. Control group VEP habituation was found for small check stimuli (P = 0.04), while potentiation was observed for medium sized checks (P = 0.02). The eight migraine patients who experienced headache within 24 h after the test tended to have increased BAEP wave IV-V ASF slopes (P = 0.08). This subgroup did also have a significant VEP habituation to small checks (P = 0.04). No correlation was found between different modalities. These results suggest that: (i) VEP habituation/potentiation state and brainstem activatio state may depend on the attack-interval cycle in migraine; (ii) VEP habituation/ potentiation may depend on spatial stimulus frequency; (iii) phonophobia (and possibly photophobia) may depend more on subcortical (brainstem) function than on cortical mechanisms; (iv) low cortical preactivation in migraine could not be confirmed; (v) EP habituation and ASF analysis may reflect sensory modality-specific, not generalized, central nervous system states in migraine and healthy control subjects.

Quantitative measurement of sound-induced discomfort and pain thresholds showed that migraineurs (n = 65) were significantly more sensitive than headache-free controls (n = 80), both during and outside attack (p < 0.0001). Patients tested with head pain had lower thresholds than those tested without pain (p < 0.01). Migraine with and without aura did not differ as to sound sensitivity. There were no significant differences in thresholds between the symptomatic and nonsymptomatic sides (p > or = 0.78). Patients with unilateral headache or pain of pulsating character were more sensitive than those with bilateral headache or pressing pain (p < 0.05). Phonophobia did not correlate significantly with duration, frequency, or severity of attacks. The main results were in accordance with a questionnaire study concerning subjective evaluation of sound sensitivity. Similarities between phonophobia and photophobia in migraine provide evidence that both phenomena share a common pathophysiological mechanism in this condition.

Questions about discomfort or pain produced by various stimuli (e.g., light, sound, exercise, neck movements) are currently used to differentiate between various primary headache disorders. In order to evaluate the usefulness of differences in sensitivity to physical stimuli in headache diagnosis, the answers to a questionnaire about sensitivity to various stimuli were compared in 68 patients with migraine, 45 with tension-type headache, 46 with cluster headache, and 23 patients with cervicogenic headache, and in 71 controls. Even among controls, a high proportion reported that many of these stimuli could elicit some degree of discomfort or pain. Without headache, migraineurs differed from the other patients with headache and controls mainly in their increased sensitivity to light. With headache, patients with tension-type headache were the least sensitive and migraineurs were the most sensitive to all stimuli, except for stimuli stemming from neck movements, to which patients with cervicogenic headache were most sensitive. Migraineurs also reported the highest degree of sensitivity regarding aggravation and provocation of headache. However, the most striking finding was that all patient groups, cluster headache in particular, became significantly more sensitive with headache than without headache to almost all stimulus categories. This may indicate that these headaches share important pathogenetic mechanisms. The fact that no headache had a very specific sensitivity profile may point to weaknesses of present headache classification systems.

Light and sound-induced discomfort and pain thresholds were measured in 26 patients with cervicogenic headache, in 40 patients with tension-type headache, and in 100 headache-free controls. Neither headache group was significantly different as to photophobia and phonophobia, but both were significantly more sensitive to light and sound than controls (p<0.0001), even when patients were tested in the headache-free period (p<0.05). Episodic and chronic tension-type headache had similar photo- and phonophobia thresholds (p> or =0.7). Tension-type headache patients were more photo- and phonophobic during headache than outside attack (p<0.05), but this was not true for cervicogenic headache (p> or =0.56). In cervicogenic headache patients, photophobia (p<0.05) but not phonophobia (p=0.28) was greater on the symptomatic side than on the non-symptomatic side.