Laser-evoked potentials in primary headaches and cranial neuralgias.

Using neurophysiological methods to explore nociceptive pathways may improve knowledge of the functional changes subtending pain processing in the different forms of headache and facial pain. Laser-evoked potentials (LEPs) are a reliable neurophysiological assay for the clinical assessment of pain syndromes. Reduced amplitude of LEPs seems to characterize trigeminal neuralgia and painful temporomandibular disorders, suggesting the neuropathic origin of pain. In tension-type headache, as well as in fibromyalgia, enhanced pericranial LEP amplitude suggests the psychogenic origin of pain. In migraine, a normal amplitude of basal LEPs with reduced habituation and altered attentive modulation seems to express a general dysfunction of cortical pain processing, which may also contribute, other than to predispose, to the persistence of migraine. LEPs may be employed in the clinical evaluation of the neurophysiological and psychophysiological aspects of pain in the different forms of headaches and facial pain to improve the therapeutic approach and provide an objective measure of treatment efficacy.