Page 118 - The clinical aspects and management of chronic migraine Judith Anne Pijpers

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Chapter 6
Discussion
This study shows that the absence of cutaneous allodynia is predictive for a good outcome after withdrawal therapy in patients with chronic migraine with medication overuse. The predictive value was even more pronounced when comparing with extracephalic allodynia, which is indicative of trigeminothalamic involvement 6–8. Our findings further suggest a migraine specific relationship because allodynia was only a strong predictor for migraine-related outcome measures.
These findings are relevant to clinical practice and current treatment concepts and expectations. Chronic migraine is a highly disabling migraine variant, in which the majority of patients overuse acute anti-headache medication 3,4,20. Withdrawal of acute medication results into reversion to episodic migraine in the majority, but not of all, patients. Previous studies at predictors for response to withdrawal treatment in mixed populations of patients with migraine or tension type headache with medication overuse, mainly showed the underlying primary headache type as predictive factor 21,22. Daily headache or daily use of medication was a predictor in univariate analysis 21,23, but did not predict outcome when adjusted for covariates 21. Psychological factors have been indicated as predictor for response 24, but require extensive assessment. This is the first study to show cutaneous allodynia as a predictor of response in chronic migraine, using a simple validated diagnostic tool for clinical practice. The effect size is moderate when comparing absence of allodynia versus allodynia in general (cohen’s d = 0.42), but increases to a moderate-large effect when considering spatial distribution, comparing no allodynia versus extracephalic allodynia (cohen’s d = 0.65). Especially with the emergence of promising, but high-cost treatment with antibodies to CGRP or its receptor 25,26, identification of predictors for response to treatment is warranted. Various trials in chronic migraine demonstrated, partly in sub-analyses, that chronic migraine patients with medication overuse will be able to respond 27,28. However, no predictors for response to monoclonal antibodies against CGRP or its receptor have yet been established 29. It is of great interest to investigate whether allodynia provides a specific predictor to chronic migraine and withdrawal therapy, or relates to other treatments in chronic migraine (with and without medication overuse) as well. Sustained exposure to acute anti-headache medication in animal models causes allodynia and an increased sensitivity to cortical spreading depression. The associated increased