Age Group for Convulsive Seizures (Febrile Seizures)
Febrile seizures occur between 6 months and 5 years of age, and this age range is a strict diagnostic criterion—seizures with fever outside this window should not be classified as febrile convulsions and require investigation for other etiologies. 1
Typical Age Range and Prevalence
- The diagnostic age window is 6 months to 5 years (or 60 months), as consistently specified by major guidelines including the American Academy of Pediatrics and the American College of Radiology 2, 1, 3
- Febrile seizures affect 2-5% of all children within this age range, making them the most common seizure disorder in pediatric patients 2, 4, 5
- Peak incidence occurs between 12 and 18 months of age, with the highest frequency of first episodes during this period 6
Critical Age-Related Clinical Implications
Age-Specific Risk of Recurrence
The age at first febrile seizure dramatically affects recurrence probability:
- Children younger than 12 months at their first febrile seizure have approximately 50% probability of recurrence 1, 7
- Children older than 12 months at their first event have approximately 30% probability of a second febrile seizure 1, 7
- Of those experiencing a second febrile seizure, 50% will have at least one additional recurrence 1
Age-Specific Management Algorithms
The approach to lumbar puncture varies critically by age:
- For infants under 12 months: Lumbar puncture is almost always indicated to rule out meningitis, given the difficulty in detecting meningeal signs in this age group 1, 7, 8
- For children 12-18 months: Lumbar puncture should probably be performed, with clinical judgment regarding meningeal signs becoming more reliable but still warranting caution 1
- For children over 18 months: Lumbar puncture is indicated only if there are clinical signs of meningism, complex features, excessive drowsiness/irritability, systemic illness, or incomplete recovery within one hour 1, 8
Critical Age-Related Pitfalls
Seizures Before 6 Months of Age
Seizures occurring before 6 months of age should NEVER be classified as febrile seizures and require thorough investigation for:
Seizures After 5 Years of Age
Seizures with fever occurring after 5 years of age should be evaluated as potential epilepsy or other neurological conditions rather than febrile convulsions 1, 3
Long-Term Prognosis by Age
- Risk of subsequent epilepsy after a simple febrile seizure is approximately 2.5% in children without complex features 1, 8
- Children experiencing prolonged febrile seizures before age 1 year warrant neurological consultation due to higher risk of complications 3
- The prognosis for developmental and neurological impairment is excellent after typical febrile convulsions within the appropriate age range 8, 5