Seasonal variations in the incidence of cranial nerve paralysis

The aim of the study was to verify whether there is a seasonal pattern in t he occurrence of cranial nerve paralysis. All patients admitted to the Emer gency Department of St Anna Hospital, Ferrara, Italy, from 1 January 1991 t o 31 December 1997, were reviewed. Cranial nerve paralysis was diagnosed in 126 cases: the oculomotor nerve accounted for 46 cases, the trochlear nerv e for 14, and the abducens nerve for 66. The frequencies of cases involving the oculomotor nerve and of all cases were significantly higher in winter than in the other seasons. Compared with other 2-month periods, the highest number of total cases occurred in November to December. Chronobiological a nalysis of the data for individual months showed a rhythmic 12-month patter n for the total population, with a weakly significant peak in January.