Febrile seizures

EDITOR – We read with interest the very informative review article
from Dr Sadler and Dr Scheffer (1) and would like to suggest that a useful
piece of information could be added, regarding the time of occurrence of
febrile seizures. In fact, a seasonal variation characterized by a winter
peak has been reported (2), with a possible association with influenza
(3). Moreover, first febrile seizures exhibit a circadian variation, with
a significant peak in the evening, between 4 to 8 PM (2).
As appropriately stated (1), it is of limited importance whether febrile
seizures are more likely to occur with the maximal rate of temperature
rise or before the fever is apparent. A close relationship between
circadian rhythms of physiological functions and diseases exists, such as
that between blood pressure rhythm and time of onset of cardiovascular
events (4-5). Also body temperature exhibits a well-known endogenous
circadian rhythm, characterized by a physiological increase during the
afternoon – evening hours and an estimated variation in amplitude up to
0.8°C (6). Thus, in some children, an even mild increase may reach the
threshold that triggers convulsions.
Although febrile seizures are a benign disorder with an excellent outcome
(1), they are particularly stressful for parents, who often develop a high
level of anxiety in the fear of recurrence. Since education and
reassurance are the mainstay of management, parents of children should be
informed about the clustering of events during winter and in the evening.

References

1) Sadler LG, Scheffer IE. Febrile seizures. BMJ 2007;334:307-311.

2) Manfredini R, Vergine G, Boari B, Faggioli R, Borgna-Pignatti C.
Circadian and seasonal variation of first febrile seizures. J Pediatr
2004;145:838-839.

3) van Zeijl JH, Mullaart RA, Borm GF, Galama JMD. Recurrence of
febrile seizures in the respiratory season is associated with influenza A.
J Pediatr 2004;145:800-805.

4) Manfredini R, Gallerani M, Portaluppi F, Fersini C. Relationships
of the circadian rhythms of thrombotic, ischemic, and arrhythmic events to
blood pressure rhythms. Ann N Y Acad Sci 1996;783:141-158.

5) Portaluppi F, Manfredini R, Fersini C. From a static to a dynamic
concept of risk: the circadian epidemiology of cardiovascular events.
Chronobiol Int 1999;16:33-49.

6) Reilly T. Circadian rhythms in muscular activity. In: Komi PV,
Marconnet P, Saltin B, Sejersted OM, eds. Muscle Fatigue Mechanisms in
Exercise and Training (Switzerland): Karger;1992;218-222.

Competing interests:
None declared