Clinical neurophysiology of headache.

Methods of clinical neurophysiology are of little use for the diagnosis of headache disorders. They are, however, invaluable tools for a better understanding of the pathophysiology of functional headaches. They are traumatic, able to explore simple or more complex neural activities, and to some extent capable of reflecting activity in certain neurotransmitter systems as well as the action of pharmacologic agents on the CNS. This article reviews the interest and limits of electroencephalography, evoked potentials, electromyography, and nocifensive reflexes in primary headaches. Because neurophysiologic methods are no more than indirect means of looking into the "black box," their results need to be interpreted with caution and, whenever possible, should be compared in the same study with clinical behavioral and biochemical data.