Background: Habituation of P300 in the migraineurs has been studied in a number of studies, but not very often in tension type headache patients. Moreover, most of the studies have used only single montage. This study assesses the habituation in migraineurs and tension type headache subjects during inter-ictal period with the help of three scalp montages., Aims and objectives: To find out if the habituation of P3 differ between the migraineurs, tension type headache subjects and controls during inter-ictal period., Methods: Study sample comprised of three groups - migraineurs, tension type headache subjects as well as a healthy control group. Fifty subjects in each group were included after screening for the respective inclusion criteria and exclusion criteria. None of the subjects were blood relatives of each other. Habituation of P3 was assessed using the frontal, central and parietal electrodes using odd-ball paradigm for target stimuli., Statistical Analysis: Data was analyzed with the help of SPSS V11.0 for Windows. Paired sample test and one way ANOVA with post-hoc tukey (wherever required) were performed., Results: P3 did not show habituation or the potentiation after successive trials in any of the group. Similarly, amplitude or latency of any of these waves was not significantly different among groups. These results were consistent among all the three scalp montages., Conclusion: In between the headache episodes, event related potentials do not habituate or potentiate, thus confirming the true episodic nature of the headache episodes.

Key Words: Migraine, tension type headache, habituation, P300