More About Febrile Seizures

Febrile seizures (FS) occur in 2-5% of children. These commonly provoked seizures typically appear as generalized tonic-clonic seizures between the ages of 6 months to 6 years associated with a fever. Simple FS occur in previously healthy, developmentally normal children and consist of brief (less than 10 minutes), symmetric convulsions. The medical evaluation following simple FS focuses on identifying a reason for the fever. While one-third of children who have FS will have at least one additional FS, most children do not require extensive medical evaluation or daily medication for seizure prevention. Simple FS is considered a common, benign condition affecting many children, and the chance of developing epilepsy later in life is only very slightly higher in children who have had FS (about 1%) compared to the general population (about 0.5%). In contrast, complex FS are defined as either prolonged or asymmetric, and children with complex FS require some further evaluation (typically EEG and MRI) to distinguish between the relatively benign condition of FS vs. epilepsy being “unmasked” by fever. 

Recent studies have also suggested that there may be a link between SUDC and FS in some children. Some children who die of SUDC have a history of febrile seizures in the recent or remote past, and/or a family history of febrile seizures, and this link between FS and SUDC is being studied. The potential link could possibly be due to FS leading to a predisposition to epilepsy, which in turn may be associated with sudden death, a very uncommon occurrence. That said, by its very definition, children who have died of SUDC have not been reported to have active seizures at or immediately leading up to the time of death. In addition, studies also show a correlation of febrile seziures to particular rare cardiac channelopathies- or abnormal inherited rythms of the heart. Brugada syndrome, specifically, can be precipitated by fever and is now regarded as a medical urgency in someone who has the syndrome. A cardiac channel molecular autopsy can examine the SCN5A gene which is responsible for 25% of Brugada syndrome.

It is also important to emphasize that in contrast to FS, SUDC, while tragic, is far less common and for the vast majority of otherwise normal children with FS, the long-term prognosis is excellent. Careful research is underway to further investigate the role FS might play in a subset of cases of SUDC, but we do not want the thousands of parents and health care providers facing FS to experience undue anxiety about this apparent connection.

 

From Our SUDC Advisory Board Members

Annapurna Poduri, M.D., M.P.H.
Division of Epilepsy and Clinical Neurophysiology
Children's Hospital Boston, Boston, MA

Ingrid A. Holm, MD, MPH
Divisions of Genetics and Endocrinology
Children's Hospital Boston, Boston, MA

Michael J. Ackerman, M.D.
Ph.D. Director, Long QT Syndrome Clinic
Pediatrics, and Molecular Pharmacology
Senior Associate Consultant in Cardiovascular Diseases
and Pediatric Cardiology
Mayo Clinic, Rochester, MN

 

Recently, we reported hippocampal abnormalities in 5 toddlers with sudden unexplained death in childhood (SUDC). The association of hippocampal anomalies with a high incidence of individual/family histories of simple febrile seizures in these cases (40%) raised concern that febrile seizures can be associated with death. In a series of 64 toddlers with sudden death, we tested the hypothesis that a SUDC subset is characterized by hippocampal maldevelopment and an individual and/or family history of simple familial seizures. Cases of sudden and unexplained death, aged 1.0-5.9 (median 1.7 years) were divided into groups based upon a history of febrile or non-febrile seizures, familial febrile seizures, and autopsy classification of cause of death. Forty-nine of the 64 cases (77%) were classified as SUDC of which 40% had an individual/family history of febrile seizures. Of the 26 SUDC cases with available hippocampal sections, 62% (16/26) had hippocampal anomalies, including 82% (9/11) of cases with an individual/family history of febrile seizures. Cases with hippocampal anomalies were all found dead during a sleep period, typically in the prone (87%) position. We conclude that a potential new entity may account for the majority of SUDC in toddlers, defined by sleep-related death in the prone position, individual/family history of febrile seizures, and hippocampal anomalies. The mechanism of death appears analogous to sudden death in (temporal lobe) epilepsy, with a putative unwitnessed seizure during sleep leading to airway occlusion and death. This study mandates further research into the potential link between simple febrile seizures and death.

PMID: 19606910 [PubMed - as supplied by publisher]