Prognosis is generally favourable.[99]Cross JH. Fever and fever-related epilepsies. Epilepsia. 2012 Sep;53(4 suppl):3-8.
https://www.doi.org/10.1111/j.1528-1167.2012.03608.x
http://www.ncbi.nlm.nih.gov/pubmed/22946716?tool=bestpractice.com
[100]Vestergaard M, Christensen J. Register-based studies on febrile seizures in Denmark. Brain Dev. 2009 May;31(5):372-7.
http://www.ncbi.nlm.nih.gov/pubmed/19203855?tool=bestpractice.com
Febrile seizures recur in approximately 30% of children during subsequent febrile illnesses.[95]Sadleir LG, Scheffer IE. Febrile seizures. BMJ. 2007 Feb 10;334(7588):307-11.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1796669
http://www.ncbi.nlm.nih.gov/pubmed/17289734?tool=bestpractice.com
Most recurrences occur within 2 years. The risk of non-febrile seizures and epilepsy developing after simple febrile seizures is 5% or less. However, after complex febrile seizures, the risk of developing epilepsy is 10% to 20%.[101]Chungath M, Shorvon S. The mortality and morbidity of febrile seizures. Nat Clin Pract Neurol. 2008 Nov;4(11):610-21.
http://www.ncbi.nlm.nih.gov/pubmed/18978801?tool=bestpractice.com
Febrile seizures are not associated with sudden unexpected death in epilepsy.[101]Chungath M, Shorvon S. The mortality and morbidity of febrile seizures. Nat Clin Pract Neurol. 2008 Nov;4(11):610-21.
http://www.ncbi.nlm.nih.gov/pubmed/18978801?tool=bestpractice.com
[102]Holm IA, Poduri A, Crandall L, et al. Inheritance of febrile seizures in sudden unexplained death in toddlers. Pediatr Neurol. 2012 Apr;46(4):235-9.
http://www.ncbi.nlm.nih.gov/pmc/articles/pmid/22490769
http://www.ncbi.nlm.nih.gov/pubmed/22490769?tool=bestpractice.com
Epidemiological data indicate that the vast majority of children with febrile seizures have a normal long-term outcome.[6]Waruiru C, Appleton R. Febrile seizures: an update. Arch Dis Child. 2004 Aug;89(8):751-6.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1720014
http://www.ncbi.nlm.nih.gov/pubmed/15269077?tool=bestpractice.com
[103]Knudsen FU. Febrile seizures: treatment and prognosis. Epilepsia. 2000 Jan;41(1):2-9.
http://www.ncbi.nlm.nih.gov/pubmed/10643916?tool=bestpractice.com
Genetic studies suggest that the relationship between febrile seizures and subsequent epilepsy and neurocognitive dysfunction is sometimes genetic, but there are complex interactions between genetic and environmental modifiers.[104]Huang CC, Chang YC. The long-term effects of febrile seizures on the hippocampal neuronal plasticity - clinical and experimental evidence. Brain Dev. 2009 May;31(5):383-7.
http://www.ncbi.nlm.nih.gov/pubmed/19131199?tool=bestpractice.com
Hippocampal abnormalities (mesial temporal sclerosis) and focal epilepsy are sometimes associated with prolonged febrile seizures.[66]Scott RC, King MD, Gadian DG, et al. Hippocampal abnormalities after prolonged febrile convulsion: a longitudinal MRI study. Brain. 2003 Nov;126(Pt 11):2551-7.
http://www.ncbi.nlm.nih.gov/pubmed/12937081?tool=bestpractice.com
Magnetic resonance imaging-detected brain abnormalities have also been reported in children following simple febrile seizures, and in adults with a history of simple febrile seizures in childhood.[105]Hesdorffer DC, Chan S, Tian H, et al. Are MRI-detected brain abnormalities associated with febrile seizure type? Epilepsia. 2008 May;49(5):765-71.
http://onlinelibrary.wiley.com/doi/10.1111/j.1528-1167.2007.01459.x/full
http://www.ncbi.nlm.nih.gov/pubmed/18070090?tool=bestpractice.com
[106]Auer T, Barsi P, Bone B, et al. History of simple febrile seizures is associated with hippocampal abnormalities in adults. Epilepsia. 2008 Sep;49(9):1562-9.
http://onlinelibrary.wiley.com/doi/10.1111/j.1528-1167.2008.01679.x/full
http://www.ncbi.nlm.nih.gov/pubmed/18503555?tool=bestpractice.com
Therefore, febrile seizures may be less benign than generally thought.
The literature appears to support a role for febrile status in the development of focal epilepsy, but febrile status is clearly neither necessary nor sufficient on its own in the focal epileptogenesis process. Multiple insults are likely necessary for a child with febrile status epilepticus to develop epilepsy later in life.[107]Ahmad S, Marsh ED. Febrile status epilepticus: current state of clinical and basic research. Semin Pediatr Neurol. 2010 Sep;17(3):150-4.
http://www.ncbi.nlm.nih.gov/pubmed/20727483?tool=bestpractice.com
One study has shown that children who have febrile seizures are at a higher risk of developing psychiatric disorders in later life.[108]Dreier JW, Pedersen CB, Cotsapas C, et al. Childhood seizures and risk of psychiatric disorders in adolescence and early adulthood: a Danish nationwide cohort study. Lancet Child Adolesc Health. 2019 Feb;3(2):99-108.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6903917
http://www.ncbi.nlm.nih.gov/pubmed/30528754?tool=bestpractice.com