Clinical neurophysiology of chronic daily headache

The pathophysiology of chronic daily headache is unclear. Clinical research aiming to elucidate causative mechanisms is often confounded by the variability of factors involved. Furthermore, there is a recent trend to use neurophysiological tests in the investigation of functional disorders in brain structures. In order to evaluate the pathophysicology of chronic daily headache, several methodologies have been employed. The aim of the present review is to relate the obtained results in the most frequently used neurophysiological tests to possible pathophysiological mechanisms of chronic daily headache. The neurophysiological findings suggest that a common neuronal dysfunction redisposes to primary headaches subtypes, whose chronicization may depend upon many factors, such as the influence of peripheral muscular factors and the dysfunction in central nociceptive modulation. These factors may explain the large variability observed in clinical features.