OBJECTIVE: Cutaneous application of menthol in healthy subjects induces cold allodynia via sensitization of cold-sensitive nociceptors. We investigated the effects of menthol on preexisting cold allodynia in patients to test whether the allodynia was exacerbated. DESIGN: In eight neuropathic pain patients (six of peripheral, two of central origin), 40% menthol was applied topically to an area of preexisting cold allodynia. Mirror-image skin areas and aged-matched healthy subjects served as controls in patients with unilateral and bilateral neuropathic pain, respectively. Prior to and after menthol, cold pain thresholds were measured using a thermotest device. RESULTS: Menthol induced significant cold allodynia in control areas. However, in neuropathic areas, results were more heterogeneous. Overall, preexisting cold allodynia was not aggravated by topical menthol and was attenuated in 6/8 patients. CONCLUSIONS: These results suggest that, unlike in controls, menthol is not more hyperalgesic, but may be analgesic in some patients with peripheral and central neuropathic pain.
OBJECTIVE: Cutaneous application of menthol in healthy subjects induces cold allodynia via sensitization of cold-sensitive nociceptors. We investigated the effects of menthol on preexisting cold allodynia in patients to test whether the allodynia was exacerbated. DESIGN: In eight neuropathic painpatients (six of peripheral, two of central origin), 40% menthol was applied topically to an area of preexisting cold allodynia. Mirror-image skin areas and aged-matched healthy subjects served as controls in patients with unilateral and bilateral neuropathic pain, respectively. Prior to and after menthol, cold pain thresholds were measured using a thermotest device. RESULTS:Menthol induced significant cold allodynia in control areas. However, in neuropathic areas, results were more heterogeneous. Overall, preexisting cold allodynia was not aggravated by topical menthol and was attenuated in 6/8 patients. CONCLUSIONS: These results suggest that, unlike in controls, menthol is not more hyperalgesic, but may be analgesic in some patients with peripheral and central neuropathic pain.