The relation of the height of the fever to the recurrence rate of febrile convulsions was studied in 154 children admitted to the Paediatric Department, Ahmadi Hospital, Kuwait. The children were divided into three groups according to the height of the fever recorded on presentation. Group 1, temperature greater than 40°C, group 2, 39-39.9°C, and group 3, 38-38.9°C. The children were followed at three month intervals for a mean of 40 months (range 2-7) and recurrences occurred between one and 22 months after the original first febrile seizure. The recurrence rates of febrile convulsions were significantly greater in infants aged 6 to 18 months in whom the initial febrile convulsions had been associated with a lower temperature. The rate of recurrence was over nine times higher in infants who had the lowest fever, 38-38.9°C and over seven times higher in infants with temperatures of 39-39.9°C. Repeated convulsions with each febrile episode occurred in only four children (3%). [1]

COMMENT. These findings are confirmation of a febrile seizure threshold dependent on the height of the fever first proposed 30 years ago [2]. It is not surprising that children who convulse with a relatively low fever have a poorer prognosis than those convulsing only with high fevers. Another factor noted in many studies to increase the risk of recurrence of febrile seizures is an early age at the first febrile seizure. Frantzen et al (1968) found that children who experienced their first seizure at less than 13 months of age had a 2.3:1 chance for developing further febrile seizures compared to a 1:2 chance when the seizure occurred between 14 and 32 months of age and a 1:5 risk when the onset was after 32 months of age. Nelson and Ellenberg (1978) found a 50% recurrence rate with the onset in the first year of life compared to a 28% recurrence rate when the onset was after the first year. The height of the fever is a most important determinant of the occurrence of febrile seizures in the infant and young child.