Role of Electroencephalogram and Neuroimaging in First Afebrile Seizure in Children: A Retrospective Study

Background: To evaluate the role of EEG and Magnetic resonance imaging (MRI) in first episode of unprovoked afebri le seizure in a child. Subjects and Methods: Data was collected retrospectively from case record s f patients admitted with seizures during the per iod between January 2016 to December 2018. All children with fi rst episode of unprovoked afebrile seizure (1-15 ye ars of age) were included in the study. Results: Case records of 108 patients with first episode of unprovoked afebrile seizures were reviewed . Out of these , 65 patients were investigated with MRI and EEG.54 children (83.1%)ha d generalized tonic clonic seizures(GTCS), 11 had p rtial seizures (16.9 %) . EEG abnormalities were seen in 21 children, predominant ly i GTCS type. The most common EEG abnormality ob served was sharp and spike wave discharges .7 children (10.7 %) had abnormal (MRI). The accuracy of MRI detecting the abnormality when EEG was abnormal was 33.3 % (p < 0.05). Conclusion: This study illustrates that routine neuroimaging fo r all children with first episode of unprovoked afe brile seizures is gratuitous. Neuroimaging can be reserved for those patients with recurrence of seizures or those child ren with clinical findings suggestive of intracranial pathologies.


Introduction
It is estimated that about 10 % of the population are known to have a seizure at some point in their lifetime. [1] Also, it accounts for about 1 % of visits to the emergency department with a high incidence among infants and young children. [2,3] The first seizure may indicate an initial presentation of epilepsy or an underlying neurological disease. The combination of seizure history, electroencephalography (EEG) and neuroimaging allows the clinician for the accurate diagnosis & early management decisions regarding antiepileptic drug therapy and surgery and also facilitates patient counseling. Although EEG is recommended as a part of the neurodiagnostic evaluation of the child with an apparent first unprovoked seizure, [4,5] the role of neuroimaging in these children is not well defined. In a few studies that have reviewed the yield of neuroimaging in children with unprovoked seizure, the prevalence of abnormalities ranged from 0% to 21%. [6][7][8] Neuroimaging (MRI) is one of the useful tool to determine the etiological diagnosis of seizure. The purpose of emergency neuroimaging is to look for the intracranial pathology that requires immediate surgical intervention in children who presents with first episode of afebrile seizure. However, there is no standard recommendation or guidelines for neuroimaging in children with unprovoked seizure. The American College of Emergency Physicians recommends neuroimaging for those younger than one year, those with cognitive or motor developmental delay, unexplained neurologic abnormalities, a history of focal seizures or findings on electroencephalography (EEG) that are incompatible with benign partial epilepsy of childhood or primary generalized epilepsy. [5] We conducted this study to evaluate the role of EEG and neuroimaging in first episode afebrile seizure.

subjects and Methods
This was a retrospective study done in the department of Paediatrics at AJ Institute of Medical Sciences, Mangalore. Data was collected from January 2016 to December 2018 using the G-health software system used for data storage of inpatients in our hospital. Individual case records were retrieved after identifying patients with seizures .Children with first episode of unprovoked afebrile seizure in whom EEG and neuroimaging was done were included in the study.

ISSN (0): 2347-3363; ISSN (P): 2347-3355
Original Article occurrence of significant EEG as well as neuroimaging findings. First unprovoked seizure (FUS) is defined as first nonfebrile seizure that cannot be explained by an immediate, obvious precipitating cause such as head trauma or intracranial infection EEG is a noninvasive, readily available and inexpensive investigation tool, helps in diagnosis of the event, identification of a specific syndrome, and prediction of longterm outcome. It also helps to differentiate a seizure from other events and predicts the risk for recurrence. [11] American EEG society recommends EEG to be performed after all first non febrile seizures. However optimal timing for obtaining EEG is not clear, EEG done within 24 hours of the seizure is most likely to show background and epileptiform abnormalities. [5,10] EEGs performed for new-onset seizures show epileptiform discharge in approximately 18% to 56% of children. [12] In our study, we found that 32.3% of children had EEG abnormalities. However in a study done by Doescher et al EEG abnormality was observed in 65.7 % of children, [13] a comparatively lower incidence of EEG abnormality noted in our study could be probably due to variable timings and method of EEG recording. Also, sometimes in remote and deep epileptic focus EEG can be normal. [10] In our study overall 71 % patients with generalized seizures had EEG abnormalities which was consistent with similar observations made by Al-Sulaiman et al, [14] and Doose et al, [15] in cases of newly diagnosed seizure. On analyzing individual abnormalities in EEG, it was observed that the most common abnormality detected was sharp wave and spikes (either alone or both) as observed by studies conducted by Baheti et al16 and Doose et al. [15] However, Shinnar et al, [17,20] Doescher et al, [15] observed a focal slowing as most common EEG abnormality which had predominantly the children with partial seizures. Neuroimaging can also be useful adjunctive tool in evaluation of a first episode of afebrile seizure but its role in paediatric patients with first episode of unprovoked seizure is still a controversy. MRI is more sensitive than CT and is the modality of choice when indicated. [10] Meta analytic studies done have shown that neuroimaging abnormalities are found in 30 % of children but clinically significant changes were seen in 13%, however it doesn't influence treatment or management decisions on hospitalization. American academy of neurology recommends emergent neuroimaging only in children who have post ictal focal deficits not resolving quickly and children not returning to baseline within several hours after the seizure. Emergency neuroimaging should be performed in a child with first afebrile seizure to look for intracranial pathologies needing immediate intervention. [5] Non urgent imaging studies with MRI should be considered in child with significant congnitive or motor impairement , focal seizures, unexplained neurological examination, age less than 1 year and EEG that doesn't show benign partial epilepsy or generalized epilepsy of childhood. [5] In our study, MRI abnormalities was seen in 7 (10.7 % ) children which was consistent with the study done by Sharma et al [18] where they found that overall incidence of neuroimaging abnormality was 8%, (26% in high risk children and 2 % in low risk) emphasizing the need of neuroimaging in only high risk category like presence of predisposing conditions and focal seizures in less than 3 years , whereas well appearing and low risk children don't warrant immediate neuroimaging. [18] However , in various studies with children evaluated for first episode of unprovoked seizures prevalence of abnormalities in the neuroimaging ranged from 0-21% [19] probably due to inclusion of non significant MRI findings as well.
Limitations of our study were small sample size, as it was retrospective study casual relationship between investigation findings and clinical condition of the patient couldn't be obtained, further studies are needed to establish the role of neuroimaging in Paediatric age group.

Conclusion
EEG is a highly useful tool in evaluating all children with first episode of unprovoked seizure. However neuroimaging with MRI is not routinely indicated in all well appearing children with afebrile seizures and should be reserved only for high risk category.