Evaluation of Clinical, EEG, and Lumbar Puncture Findings of Patients with Complicated Febrile Seizure

Introduction

Febrile seizure (convulsion) (FC) is a type of seizure accompanied by fever, without a history of neurological disease and central nervous system infection¹. It is a relatively common condition in the general pediatric population. It occurs in approximately 2–5% of children aged between 6 months and 5 years². FCs are divided into three groups: (1) Simple FC, (2) complex FC, and (3) febrile status epilepticus. Simple FC is a generalized seizure that reoccurs once in 24 h and lasts <15 min. About 70–75% of patients experience simple FC. Complex FC is type of seizure that is accompanied by focal seizures which reoccur within 24 h and/or lasts longer than 15 min. About 20–25% of patients experience complex FC. Febrile status is a type of seizure in which the duration of the seizure exceeds 30 min³. A Category 4 has emerged recently that describes a subset of complex FC called febrile seizure plus (FS+). FS+ includes simple febrile seizures occurring more than once in 24 h and underlying immunological events are suspected⁴. Among the new definitions, there is also genetic epilepsy with febrile seizures plus subgroup (GEFS+) which has a genetic origin and febrile infection related epilepsy syndrome (FIRES) subgroup with possible immunological origin triggered by any infection^5,6.

Although lumbar puncture (LP) is not a routine method applied to every patient in FC, it is a method that we frequently apply. LP procedure can be applied if the presence of meningeal signs and symptoms and/or the history of the child increases the possibility of intracranial infection, Hemophilus influenzae Type b or Streptococcus pneumoniae vaccines have not been administered in a 6–12-month-old baby or the immunization status is unknown, and if meningitis findings are thought to be shadowed in patients who have recently received antibiotic therapy³. Although electroencephalography (EEG) is not a routine method used in FC, it can be used in some patient groups to determine the presence of epilepsy, to determine the severity of encephalopathy and central nervous system infection. It is frequently preferred in complex FC and it is recommended to be taken 14 days after the seizure⁷.

Materials and Methods

Our study included 45 patients who applied to Aydın State Hospital Pediatric Neurology Clinic between July 2018 and July 2020 and Mersin City Training and Research Hospital between October 2020 and October 2021 with complex febrile seizures. Our study was carried out as a retrospective patient file scan. Patients with a previous diagnosis of epilepsy, regular use of antiepileptic agents or febrile seizure prophylaxis, followed up with neurometabolic and neurogenetic diagnoses, and patients with a history of trauma were excluded from the study. Patients presenting with complex FC were included in the study. Patients presenting with febrile status epilepticus and simple FC and patients diagnosed with metabolic disease as a result of investigations were not included in the study. Patients presenting with febrile status epilepticus were not included in the study.

Results

Two hundred and seven patients with FC were admitted to our clinic. Forty-five (21.7%) of these patients had complex FC. Forty-five patients diagnosed with complex FC were included in the study. The mean age of the patients was 16.6 months and the age range was between 6 and 58 months. Twenty-five (55.5%) of our patients were male and 20 (44.5%) were female. There was a family history of FC in 9 (20%) of 45 patients. Eight (17.7%) patients underwent cranial imaging. Cranial CT was performed in five patients and the results were normal. Cranial MRI was performed in five patients. LP was performed in 29 (64.4%) patients, EEG was performed in 40 (88.9%) patients. Among our patients, 10 (22.2%) patients had focal seizures, 15 (33.3%) patients had seizures longer than 15 min, and 25 (55.5%) patients had recurrent seizures within 24 h (Table 1).

If the CSF cell count was >5/mm³, it was considered as pleocytosis. Pleocytosis was detected in three (6.7%) patients, S. pneumonia was detected in CSF culture in one patient. H1N1 encephalitis was also observed in one of our patients. Sign of encephalitis due to H1N1 infection was observed on cranial imaging in one patient (Figure 1). In all three patients, seizure recurrence within 24 h and recurrent seizures lasting longer than 15 min were present. Besides the patient, who was diagnosed with S. pneumonia, had meningeal irritation findings on repeated examinations and the patient who was diagnosed with H1N1 encephalitis had postictal neurological findings. Forty (88.9%) patients underwent EEG within the 1^st month. EEG abnormalities were detected in 5 (11.1%) patients. Three of the five patients with EEG abnormalities were patients in whom pleocytosis was detected in the CSF. The other two patients were considered to have epilepsy and were followed up with antiepileptic therapy.

Close

Figure 1.

Hyperintense areas on MRI of the patient diagnosed with H1N1 encephalitis.

Export to PPT

Discussion

FCs, which are the most common seizure type in childhood, are more common in boys than girls and the M/F ratio is 1.2–1.41. Tsuboi reported the M/F ratio as 1.42 in children with FC^8,9. In our study, this ratio was detected as 1.25. Its high prevalence in male individuals has been associated with being more prone to infections¹⁰. Özaydın et al. followed up 1245 (89.8%) patients with simple FC and 140 patients (10.2%) with complex FC among a study group including 1385 patients¹¹. Aygün et al. observed in their study group that the ratio of simple FC was 69% and complex FC was 31%¹². While this ratio was 66/34% in the study of Yılmaz et al., Şen et al. determined this ratio as 76.2/23.8% in their study^13,14. In our study, 45 (21.7%) of 207 patients were followed up with complex FC. It is reported in the literature that the children with FC have a history of FC in their families and in their siblings with a ratio of 25–40% and 9–22%, respectively¹⁵. In our study, 20% of the patients had a family history. The fact that this rate was relatively low compared to the literature was attributed to the fact that we accepted the complex FC as our study sample.

According to Camfield et al., FCs lead to 15% of childhood-onset epilepsy¹⁶. In our study, the diagnosis of epilepsy was considered in two patients and they were followed-up^4,5. In the study of Biçer et al., a pathology was observed in the EEG in 53.8% of patients with complex FC, and in 37.4% of patients with simple FC¹⁷. In a study of Akbaş et al., EEG abnormality was observed in 24% of the patients. Focal epileptic discharges were observed in all patients with abnormal EEG. No generalized or multifocal discharge was observed¹⁸. In our study, EEG abnormalities were observed in 5 (12.5%) of 40 patients whose EEG was performed.

Application of LP procedure is controversial. Although the association of fever and convulsion in meningitis is <5%; LP should be performed in patients with focal seizures, raised fontanel, rash (petechiae, purpura), hypotension, cyanosis, and abnormal neurological findings. LP should be performed especially in babies younger than 12 months of age, presenting with fever and convulsions, since clinical signs of meningitis will not be evident, and it should not be routinely performed in children older than 18 months^19,20. In our study, LP was performed in 29 (64.4%) patients, and pleocytosis was detected in 3 (6.7%) patients. S. pneumonia was detected in CSF culture in one patient, and H1N1 encephalitis was observed in one patient.

Conclusion

The presence of postictal neurologic findings in our study were considered to be the most important risk factor for CNS infections. It was thought that the detection of epileptiform abnormality in the EEGs of the patients might be related to the shorter period after the seizure.