Allodynia, Phonophobia Appear Linked in Migraineurs

BY JOHN R. BELL
Elsevier Global Medical News

BOSTON (EGMN) - Migraineurs with allodynia also are likely to have phonophobia, according to a report presented as a poster May 2 at the annual meeting of the American Academy of Neurology.

Dr. Avi Ashkenazi of Thomas Jefferson University, Philadelphia, and colleagues based their conclusion on studies of 25 women and 2 men with episodic migraines and normal audiograms.

They tested the study participants for phonophobia and ascribed a sound sensitivity threshold based on response to a repeated sound stimulus. The stimulus had three ascending frequencies (1,000, 4,000, and 8,000 Hz) that were increased in volume from 50 dB to 110 dB until the participants reported that the sound was painful or bothersome. The sound stimuli were administered using the PsychRP psychoacoustic software. Participants also were tested for brush allodynia via stimulation with a gauze pad applied to three different skin areas. Participants were tested for allodynia and phonophobia between migraine attacks and during an untreated migraine.

Of the 27 participants, 18 were examined both during an acute migraine attack and between attacks. Of those 18 participants, 14 (78%) had allodynia, and 4 (22%) did not. During migraines, sound sensitivity thresholds were lower for the entire study cohort, but the differences were statistically significant only among those with allodynia, and the differences were significant at every level of sound stimulus, decreasing by 16 dB at 1,000 Hz, 13 dB at 4,000 Hz, and 14 dB at 8,000 Hz. For the nonallodynic group, there were no significant differences in sound sensitivity thresholds at any frequency level.

These results "suggest an association between cutaneous allodynia and phonophobia in migraine," Dr. Ashkenazi and colleagues concluded. They noted that both skin and sound sensitivity have previously been identified as more common among migraine patients.

This multiple sensitivity "has implications for the mechanisms of both allodynia and phonophobia," Dr. Ashkenazi said in an interview. "I think it's a generalized cortical hyperexcitability that involves all areas of the sensory cortex, from the visual to the tactile - to the somatosensory cortex to the auditory cortex. So it's not a specific mechanism that involves one specific sensory modality." He surmised that it likely is associated with cortical spreading depression.

Dr. Ashkenazi received a grant from Merck and Co., and his colleagues were supported by Allergan, NPS Pharmaceuticals, UCB Pharma, RW Johnson, Pfizer Inc., AstraZeneca, and Integrated Therapeutics Inc.

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