Seasonal variation of Bell's palsy in Athens, Greece - a hospital-based retrospective evaluation over fifteen years.

Epidemiological data on the incidence of Bell's palsy (BP) are conflicting. The aim of this retrospective study was to evaluate the variation of cases of BP acutely presented in the emergency room of our department over a 15-year period (January 1990 to December 2004). We examined the monthly and seasonal distribution of BPs among 36,312 patients who came to our emergency services and compared it with the assumed equal distribution of cases over the year (null hypothesis) using chi(2) techniques. During the observation period 1,252 of all patients (3.45%) presented due to BP. A decline during the summer was observed, in contrast to a peak documented during the autumn and winter. January and July were the months with the highest and lowest frequency of BP, respectively. Statistical analysis revealed a significantly different seasonal (chi(2) = 10.569; d.f. = 3; p = 0.014) and monthly (chi(2) = 25.445; d.f. = 11; p = 0.008) pattern of BP cases. The distribution of cases of BP shows a significant variation with a decline during the summer and an increase during the colder period of the year. A similar pattern has been described for reactivated herpetic ocular infections. Since a similar pathogenetic mechanism is regarded as the main cause of BP, the chronobiological aspects and the influence of meteorological factors on the reactivation of latent infections deserves further prospective evaluation.