The clinical neurophysiology of tension-type headache

Despite being widely investigated, the pathogenesis of tension-type headache (TTH) continues to be debated. Among the different approaches used to explore the mechanisms underlying TTH, clinical neurophysiology plays an important role. Studies to date have focused mainly on two areas: (1) evaluation of peripheral factors (i.e., by electromyography (EMG)); and (2) exploration of the role of the pain control system. In the second of these areas, a large number of studies have explored trigeminal pathways, in particular using reflexes (e.g., the trigeminofacial reflex, trigeminotrigeminal reflexes). More recently, the descending inhibitory system, known to modulate both the trigeminal and the spinal system, has also been investigated. In addition, several studies have sought to establish whether there are neurophysiological parameters that could be markers of this condition, but the results of these were inconclusive, since some abnormalities could frequently be observed in migraine too. This chapter critically reviews the clinical neurophysiology of TTH. It concludes that the majority of neurophysiological studies on TTH present serious methodological flaws that will have to be overcome to allow further understanding of the mechanisms of TTH.