The epidemiology of headache and migraine, and its meaning for neurological services.

: Estimates of the incidence and prevalence of migraine and tension-type headache are strongly dependent upon the diagnostic criteria employed. The inter-rater reliability of classification of different types of headache is poor. Whatever the "true" prevalence of headache and migraine, the demand for neurological services is culturally determined. A small alteration in tolerance of a population's headaches may lead to a demand for a greatly increased number of neurologists.