NEUROLOGÍA

Introduction: We analyze the diagnostic utility of urgent EEG (electroencephalogram) performed in children under 16 years of age in our center

EEG is increasingly being used in other indications not directly associated with epilepsy.Given the challenge of history taking in paediatric patients, and especially in infants and children younger than 5 years, the availability of a technically simple, painless test not requiring sedation may be very useful for other conditions.
[16][17][18][19][20][21][22][23] Assessing the accuracy of neurological diagnostic tests performed in each centre is very useful, not only for physicians working there but also for other professionals to assess and compare the results.
We analyse the diagnostic usefulness of EEG recording at the emergency department in children aged 16 years or younger at our hospital.

Materials and methods
This is a descriptive, observational, retrospective study of consecutive patients aged 0 to 16 years who underwent emergency EEG at our hospital for any reason, either at the emergency department, on the inpatient ward, or in outpatient consultations.The inclusion period was from January to December 2022.
The variables analysed were: age of the patient, sex, history of epilepsy, age at epilepsy diagnosis, previous treatment with

Results
We identified a total of 418 emergency EEG studies during the study period.Of this total, 388 are different patients, and 20 are registries of patients who underwent another emergency study on the same day or very soon after.
Of the 70 EEG studies, 18 (25.71%)were performed in admitted patients, 48 (68.57%) at the emergency department, and the remaining 4 (5.71%) were requested by outpatient consultations.In terms of time of performance, 67 (95.71%) were performed within the first 24 hours, and 3 (4.28%)within 48 hours after the event.
Of the 70 studies, 47 yielded normal results (67.14%).The findings in the remaining 23   Aetiology was metabolic in the 2 patients presenting symptoms of encephalopathy with altered EEG recording (generalised slowing with theta activity and generalised delta waves).The 3 patients diagnosed with SE showed a burst-suppression pattern of generalised activity in the EEG recording.
Of the 47 patients with suspected epilepsy, 20 showed EEG abnormalities; in 19 of these, diagnosis was clinically confirmed and specific treatment started (epilepsy, encephalopathy/encephalitis, or SE).None of the patients with suspected syncope or paroxysmal disorder (17 patients, 24.28%) presented EEG abnormalities.Of the 17 patients with atypical febrile seizures, 3 presented EEG alterations (2 displayed epileptic foci, and the other met criteria for encephalopathy).
Of the 47 patients with normal EEG results, 10 were diagnosed with epilepsy, and 3 of these received antiepileptic treatment at discharge.The remaining patients were only indicated occasional benzodiazepines for new seizures.
Of the total 70 patients, 3 (4.28%)required ICU admission, and 35 (50%) were admitted to the paediatric or neurology ward to complete the diagnostic study.No death was reported in our series.

Discussion
After reviewing the emergency activity at our hospital's paediatric department, we identified a very high number of consultations (approximately 40,000 annual visits, with a mean of 100-110 patients daily, and peaks of 150 patients daily in winter) for the size of the centre (267 beds) and the assigned population (325,000 people in 2022).1][22][23] Considering the volume of patients attended, the number of EEG studies requested is low; this raised the question of what the main indications were and how accurate the study was in these cases.
Less than a tenth of patients in our series had previously been diagnosed with epilepsy; therefore, EEG was mainly requested for a de novo diagnosis, which was achieved in more than one-third of the patients.In patients with known epilepsy, EEG was indicated due to a change in the type of seizure or unusually long seizure duration.
The most surprising finding is that almost 25% of patients with atypical febrile seizures showed EEG alterations.The accuracy of EEG in our series seems higher than in previous series, probably due to the proximity to the event (almost all EEG studies were performed in the first 48 hours).Patients with paroxysmal events or syncope presented normal EEG results, as in previous series. 17  Almost half of patients with strongly suspected epilepsy or SE presented EEG abnormalities, and diagnosis was clinically confirmed in nearly all of them, leading to specific antiepileptic treatment (epilepsy, encephalopathy/encephalitis, or SE); therefore, the accuracy of the test in this group of patients seems clear, and influences the physician's approach.In the single patient with clinical suspicion and EEG abnormalities in whom diagnosis was not confirmed, this was due to dissociation between clinical symptoms and location of the EEG focus.In the remaining patients, clinical suspicion prevailed despite a normal EEG recording, pending confirmation in a follow-up visit to the paediatric neurology consultation scheduled at discharge.No case of strongly suspected epilepsy was ruled out due to normal EEG The percentage of SE in our series is very low, in terms of both clinical suspicion and final diagnosis.Many cases of refractory epilepsies, epileptic encephalopathies, and syndromic/metabolic diseases in paediatric patients are referred to tertiary care centres, so the low prevalence of SE in our centre may be associated with this degree of complexity.
The final diagnoses are very heterogeneous, although they are the typical diagnoses at the paediatric emergency department. 3,4,8,9In patients diagnosed with probable epilepsy (focal or generalised), the majority of treatments consisted of timely administration of benzodiazepines rather than preventive treatment with AED, according to the typical recommendations for this age group.If clinical doubts remained after a first emergency EEG recording showing normal results, a longer, sleep-deprived EEG recording (90 minutes) was indicated.In this series, no patient was directly referred from the emergency department for overnight video-EEG monitoring, as this resource is reserved for specialists at the paediatric neurology department.
One limitation of our study, in addition to its small sample size, is the variability in the reasons for consultations and final diagnoses, which complicated the analysis of results.Although the reasons for consultations were fairly clear, and may be grouped into frequent causes (febrile or afebrile seizures, syncope, paroxysmal events, etc), the final diagnoses were rather heterogeneous.
Another important limitation is the lack of follow-up of cases of SE in our series, as a result of which we do not know the aetiology and final outcome (all cases were transferred to other centres with paediatric ICU).With this in mind, the absence of mortality in our series may be due to underestimation.
The usefulness of emergency EEG in epileptic seizures is widely reported; however, the technique is also used in children whose symptoms are less specific, or difficult to categorise due to the challenging task of history-taking in this age group.We consider the study to offer an added value in these cases.

Conclusions
One-third of the EEG recordings at the emergency department showed alterations, which is higher than the rates reported in other published series, probably due to the time of EEG performance.Almost half of patients with suspected epilepsy or SE showed EEG abnormalities, which confirmed the diagnosis in these cases and favoured the onset of pharmacological treatment.Strongly suspected epilepsy was not ruled out due to normal EEG recording in any case in our series.
No patient diagnosed with syncope or paroxysmal disorder presented EEG alterations.Almost 25% of patients with atypical febrile seizures showed EEG alterations.Very few cases of SE were recorded, probably due to our centre's high degree of clinical complexity.

Figure 1
Figure 1 Box-and-whisker plot of the age and sex of patients.

Figure 2
Figure 2 Histogram of the age at diagnosis of epilepsy of the patients in our series.

Figure 3 Figure 4
Figure 3 Reasons for consultation.

Figure 6
Figure 6 Pharmacological treatment at discharge in our series.

Table 1
Mean age at epilepsy diagnosis and at EEG performance at the emergency department, adjusted by sex.