AUDITORY EVEN-RELATED BRAIN POTENTIALS IN HYPERTHYROIDISM

Several studies based on psychometric tests have demostrated an impair ment of cognitive functions in hyperthyroid patients. Long-latency au ditory event related potentials (ERPs) allow the measurement of a kind of cerebral reaction time that is unavailable to psychometric tests. However, ERPs alterations in hyperthyroidism have been investigated on ly, in experimentally induced hyperthyroidism in healthy subjects, but no study has reported on thyrotoxic patients so far. Therefore, we in vestigated alterations of P300 wave latency in hyperthyroid patients b efore and after antithyroid treatment. ERPs were elicited in 20 untrea ted patients with hyperthyroidism (mean age :27.40 +/- 2.10 years) and in 30 sex-, age- and education-matched controls. ERPs recordings were repeated 4 months after attainment of euthyroidism. Untreated patient s had longer mean P300 latencies when compared to those in controls (3 38.3 +/- 26.6 vs 320.7 +/- 16.2 msec, P = 0.020). Slowing of P300 late ncy was marked in 4 of 20 patients and its normalization was observed after treatment. The mean P300 latencies also returned to normal (320. 5 +/- 15.5 msec) 4 months after achievement of euthyroidism. Our study shows that P300 is normal in most cases, while we have found in a sub group of patients a small but statistically significant slowing. Howev er, these alterations are reversed 4 months after attainment of euthyr oidism.