Medication overuse headache (MOH): complication of migraine or secondary headache?

In the field of chronic forms of headache, medication overuse headache (MOH) seems to be a problematic argument as the correct position of this clinical condition in the International Headache Society (IHS) classification is not clear yet. In 1988, when IHS organized the first classification of the different forms of headache, the clinical problem of medication overuse was included in the section eight of the IHS; during the last decades the criteria of the classification changed, and now this form is included in the classification system as a clinical condition distinguished from chronic migraine and other chronic forms of headache. The different models of classification are discussed and the clinical and practical aspects are considered in this paper.