[Neurophysiological studies of headaches]. / Estudios neurofisiológicos en cefaleas.

INTRODUCTION AND OBJECTIVE: The diagnosis of headache is based on the clinical criteria suggested by the IHS in 1988. The neurophysiological examinations often used in the study of headache may support the clinical diagnosis and give information as to the prognosis. The objective of this paper is to review the neurophysiological examinations most often used in the clinical and pathological investigation of headache. DEVELOPMENT: As shown by recent studies, the EEG is of little value in the routine evaluation of a patient with headache. However, it may be useful as an exploratory test for underlying pathology in atypical headache or when intra-cranial pathology is suspected. Evoked potentials, when used to study migraine, show absence of Habituation (or Potentiation) in migraine patients. This finding may represent abnormality in the processing of information at a cortical level in these patients. There is a tendency to unify the theory of neurone hypoxia and the absence of Habituation in Migraine as a single hypothesis of pathogenesis. Negative Contingent Variation has proved to be clinically useful to optimize treatment in Migraine. The electromyogram and Muscle Reflexes have been used in the study of Tension Type Headaches, ES2 changes, showing brainstem antinociceptive reflexes support the participation of a central factor in the origin of chronic Tension Headache. CONCLUSION: Neurophysiological tests may be useful in investigation of the pathology of headache since they permit a functional study of many neurone paths and the action of drugs on the central nervous system.